b9c6820f02
The sub-buffer pages are held in an unsigned long array, and when it is
passed to virt_to_page() a cast is needed.
Link: https://lore.kernel.org/all/20240515124808.06279d04@canb.auug.org.au/
Link: https://lore.kernel.org/linux-trace-kernel/20240515010558.4abaefdd@rorschach.local.home
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Fixes: 117c39200d
("ring-buffer: Introducing ring-buffer mapping functions")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
6870 lines
182 KiB
C
6870 lines
182 KiB
C
// SPDX-License-Identifier: GPL-2.0
|
|
/*
|
|
* Generic ring buffer
|
|
*
|
|
* Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
|
|
*/
|
|
#include <linux/trace_recursion.h>
|
|
#include <linux/trace_events.h>
|
|
#include <linux/ring_buffer.h>
|
|
#include <linux/trace_clock.h>
|
|
#include <linux/sched/clock.h>
|
|
#include <linux/cacheflush.h>
|
|
#include <linux/trace_seq.h>
|
|
#include <linux/spinlock.h>
|
|
#include <linux/irq_work.h>
|
|
#include <linux/security.h>
|
|
#include <linux/uaccess.h>
|
|
#include <linux/hardirq.h>
|
|
#include <linux/kthread.h> /* for self test */
|
|
#include <linux/module.h>
|
|
#include <linux/percpu.h>
|
|
#include <linux/mutex.h>
|
|
#include <linux/delay.h>
|
|
#include <linux/slab.h>
|
|
#include <linux/init.h>
|
|
#include <linux/hash.h>
|
|
#include <linux/list.h>
|
|
#include <linux/cpu.h>
|
|
#include <linux/oom.h>
|
|
#include <linux/mm.h>
|
|
|
|
#include <asm/local64.h>
|
|
#include <asm/local.h>
|
|
|
|
/*
|
|
* The "absolute" timestamp in the buffer is only 59 bits.
|
|
* If a clock has the 5 MSBs set, it needs to be saved and
|
|
* reinserted.
|
|
*/
|
|
#define TS_MSB (0xf8ULL << 56)
|
|
#define ABS_TS_MASK (~TS_MSB)
|
|
|
|
static void update_pages_handler(struct work_struct *work);
|
|
|
|
/*
|
|
* The ring buffer header is special. We must manually up keep it.
|
|
*/
|
|
int ring_buffer_print_entry_header(struct trace_seq *s)
|
|
{
|
|
trace_seq_puts(s, "# compressed entry header\n");
|
|
trace_seq_puts(s, "\ttype_len : 5 bits\n");
|
|
trace_seq_puts(s, "\ttime_delta : 27 bits\n");
|
|
trace_seq_puts(s, "\tarray : 32 bits\n");
|
|
trace_seq_putc(s, '\n');
|
|
trace_seq_printf(s, "\tpadding : type == %d\n",
|
|
RINGBUF_TYPE_PADDING);
|
|
trace_seq_printf(s, "\ttime_extend : type == %d\n",
|
|
RINGBUF_TYPE_TIME_EXTEND);
|
|
trace_seq_printf(s, "\ttime_stamp : type == %d\n",
|
|
RINGBUF_TYPE_TIME_STAMP);
|
|
trace_seq_printf(s, "\tdata max type_len == %d\n",
|
|
RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
|
|
|
|
return !trace_seq_has_overflowed(s);
|
|
}
|
|
|
|
/*
|
|
* The ring buffer is made up of a list of pages. A separate list of pages is
|
|
* allocated for each CPU. A writer may only write to a buffer that is
|
|
* associated with the CPU it is currently executing on. A reader may read
|
|
* from any per cpu buffer.
|
|
*
|
|
* The reader is special. For each per cpu buffer, the reader has its own
|
|
* reader page. When a reader has read the entire reader page, this reader
|
|
* page is swapped with another page in the ring buffer.
|
|
*
|
|
* Now, as long as the writer is off the reader page, the reader can do what
|
|
* ever it wants with that page. The writer will never write to that page
|
|
* again (as long as it is out of the ring buffer).
|
|
*
|
|
* Here's some silly ASCII art.
|
|
*
|
|
* +------+
|
|
* |reader| RING BUFFER
|
|
* |page |
|
|
* +------+ +---+ +---+ +---+
|
|
* | |-->| |-->| |
|
|
* +---+ +---+ +---+
|
|
* ^ |
|
|
* | |
|
|
* +---------------+
|
|
*
|
|
*
|
|
* +------+
|
|
* |reader| RING BUFFER
|
|
* |page |------------------v
|
|
* +------+ +---+ +---+ +---+
|
|
* | |-->| |-->| |
|
|
* +---+ +---+ +---+
|
|
* ^ |
|
|
* | |
|
|
* +---------------+
|
|
*
|
|
*
|
|
* +------+
|
|
* |reader| RING BUFFER
|
|
* |page |------------------v
|
|
* +------+ +---+ +---+ +---+
|
|
* ^ | |-->| |-->| |
|
|
* | +---+ +---+ +---+
|
|
* | |
|
|
* | |
|
|
* +------------------------------+
|
|
*
|
|
*
|
|
* +------+
|
|
* |buffer| RING BUFFER
|
|
* |page |------------------v
|
|
* +------+ +---+ +---+ +---+
|
|
* ^ | | | |-->| |
|
|
* | New +---+ +---+ +---+
|
|
* | Reader------^ |
|
|
* | page |
|
|
* +------------------------------+
|
|
*
|
|
*
|
|
* After we make this swap, the reader can hand this page off to the splice
|
|
* code and be done with it. It can even allocate a new page if it needs to
|
|
* and swap that into the ring buffer.
|
|
*
|
|
* We will be using cmpxchg soon to make all this lockless.
|
|
*
|
|
*/
|
|
|
|
/* Used for individual buffers (after the counter) */
|
|
#define RB_BUFFER_OFF (1 << 20)
|
|
|
|
#define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data)
|
|
|
|
#define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
|
|
#define RB_ALIGNMENT 4U
|
|
#define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
|
|
#define RB_EVNT_MIN_SIZE 8U /* two 32bit words */
|
|
|
|
#ifndef CONFIG_HAVE_64BIT_ALIGNED_ACCESS
|
|
# define RB_FORCE_8BYTE_ALIGNMENT 0
|
|
# define RB_ARCH_ALIGNMENT RB_ALIGNMENT
|
|
#else
|
|
# define RB_FORCE_8BYTE_ALIGNMENT 1
|
|
# define RB_ARCH_ALIGNMENT 8U
|
|
#endif
|
|
|
|
#define RB_ALIGN_DATA __aligned(RB_ARCH_ALIGNMENT)
|
|
|
|
/* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */
|
|
#define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX
|
|
|
|
enum {
|
|
RB_LEN_TIME_EXTEND = 8,
|
|
RB_LEN_TIME_STAMP = 8,
|
|
};
|
|
|
|
#define skip_time_extend(event) \
|
|
((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND))
|
|
|
|
#define extended_time(event) \
|
|
(event->type_len >= RINGBUF_TYPE_TIME_EXTEND)
|
|
|
|
static inline bool rb_null_event(struct ring_buffer_event *event)
|
|
{
|
|
return event->type_len == RINGBUF_TYPE_PADDING && !event->time_delta;
|
|
}
|
|
|
|
static void rb_event_set_padding(struct ring_buffer_event *event)
|
|
{
|
|
/* padding has a NULL time_delta */
|
|
event->type_len = RINGBUF_TYPE_PADDING;
|
|
event->time_delta = 0;
|
|
}
|
|
|
|
static unsigned
|
|
rb_event_data_length(struct ring_buffer_event *event)
|
|
{
|
|
unsigned length;
|
|
|
|
if (event->type_len)
|
|
length = event->type_len * RB_ALIGNMENT;
|
|
else
|
|
length = event->array[0];
|
|
return length + RB_EVNT_HDR_SIZE;
|
|
}
|
|
|
|
/*
|
|
* Return the length of the given event. Will return
|
|
* the length of the time extend if the event is a
|
|
* time extend.
|
|
*/
|
|
static inline unsigned
|
|
rb_event_length(struct ring_buffer_event *event)
|
|
{
|
|
switch (event->type_len) {
|
|
case RINGBUF_TYPE_PADDING:
|
|
if (rb_null_event(event))
|
|
/* undefined */
|
|
return -1;
|
|
return event->array[0] + RB_EVNT_HDR_SIZE;
|
|
|
|
case RINGBUF_TYPE_TIME_EXTEND:
|
|
return RB_LEN_TIME_EXTEND;
|
|
|
|
case RINGBUF_TYPE_TIME_STAMP:
|
|
return RB_LEN_TIME_STAMP;
|
|
|
|
case RINGBUF_TYPE_DATA:
|
|
return rb_event_data_length(event);
|
|
default:
|
|
WARN_ON_ONCE(1);
|
|
}
|
|
/* not hit */
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Return total length of time extend and data,
|
|
* or just the event length for all other events.
|
|
*/
|
|
static inline unsigned
|
|
rb_event_ts_length(struct ring_buffer_event *event)
|
|
{
|
|
unsigned len = 0;
|
|
|
|
if (extended_time(event)) {
|
|
/* time extends include the data event after it */
|
|
len = RB_LEN_TIME_EXTEND;
|
|
event = skip_time_extend(event);
|
|
}
|
|
return len + rb_event_length(event);
|
|
}
|
|
|
|
/**
|
|
* ring_buffer_event_length - return the length of the event
|
|
* @event: the event to get the length of
|
|
*
|
|
* Returns the size of the data load of a data event.
|
|
* If the event is something other than a data event, it
|
|
* returns the size of the event itself. With the exception
|
|
* of a TIME EXTEND, where it still returns the size of the
|
|
* data load of the data event after it.
|
|
*/
|
|
unsigned ring_buffer_event_length(struct ring_buffer_event *event)
|
|
{
|
|
unsigned length;
|
|
|
|
if (extended_time(event))
|
|
event = skip_time_extend(event);
|
|
|
|
length = rb_event_length(event);
|
|
if (event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
|
|
return length;
|
|
length -= RB_EVNT_HDR_SIZE;
|
|
if (length > RB_MAX_SMALL_DATA + sizeof(event->array[0]))
|
|
length -= sizeof(event->array[0]);
|
|
return length;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_event_length);
|
|
|
|
/* inline for ring buffer fast paths */
|
|
static __always_inline void *
|
|
rb_event_data(struct ring_buffer_event *event)
|
|
{
|
|
if (extended_time(event))
|
|
event = skip_time_extend(event);
|
|
WARN_ON_ONCE(event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX);
|
|
/* If length is in len field, then array[0] has the data */
|
|
if (event->type_len)
|
|
return (void *)&event->array[0];
|
|
/* Otherwise length is in array[0] and array[1] has the data */
|
|
return (void *)&event->array[1];
|
|
}
|
|
|
|
/**
|
|
* ring_buffer_event_data - return the data of the event
|
|
* @event: the event to get the data from
|
|
*/
|
|
void *ring_buffer_event_data(struct ring_buffer_event *event)
|
|
{
|
|
return rb_event_data(event);
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_event_data);
|
|
|
|
#define for_each_buffer_cpu(buffer, cpu) \
|
|
for_each_cpu(cpu, buffer->cpumask)
|
|
|
|
#define for_each_online_buffer_cpu(buffer, cpu) \
|
|
for_each_cpu_and(cpu, buffer->cpumask, cpu_online_mask)
|
|
|
|
#define TS_SHIFT 27
|
|
#define TS_MASK ((1ULL << TS_SHIFT) - 1)
|
|
#define TS_DELTA_TEST (~TS_MASK)
|
|
|
|
static u64 rb_event_time_stamp(struct ring_buffer_event *event)
|
|
{
|
|
u64 ts;
|
|
|
|
ts = event->array[0];
|
|
ts <<= TS_SHIFT;
|
|
ts += event->time_delta;
|
|
|
|
return ts;
|
|
}
|
|
|
|
/* Flag when events were overwritten */
|
|
#define RB_MISSED_EVENTS (1 << 31)
|
|
/* Missed count stored at end */
|
|
#define RB_MISSED_STORED (1 << 30)
|
|
|
|
#define RB_MISSED_MASK (3 << 30)
|
|
|
|
struct buffer_data_page {
|
|
u64 time_stamp; /* page time stamp */
|
|
local_t commit; /* write committed index */
|
|
unsigned char data[] RB_ALIGN_DATA; /* data of buffer page */
|
|
};
|
|
|
|
struct buffer_data_read_page {
|
|
unsigned order; /* order of the page */
|
|
struct buffer_data_page *data; /* actual data, stored in this page */
|
|
};
|
|
|
|
/*
|
|
* Note, the buffer_page list must be first. The buffer pages
|
|
* are allocated in cache lines, which means that each buffer
|
|
* page will be at the beginning of a cache line, and thus
|
|
* the least significant bits will be zero. We use this to
|
|
* add flags in the list struct pointers, to make the ring buffer
|
|
* lockless.
|
|
*/
|
|
struct buffer_page {
|
|
struct list_head list; /* list of buffer pages */
|
|
local_t write; /* index for next write */
|
|
unsigned read; /* index for next read */
|
|
local_t entries; /* entries on this page */
|
|
unsigned long real_end; /* real end of data */
|
|
unsigned order; /* order of the page */
|
|
u32 id; /* ID for external mapping */
|
|
struct buffer_data_page *page; /* Actual data page */
|
|
};
|
|
|
|
/*
|
|
* The buffer page counters, write and entries, must be reset
|
|
* atomically when crossing page boundaries. To synchronize this
|
|
* update, two counters are inserted into the number. One is
|
|
* the actual counter for the write position or count on the page.
|
|
*
|
|
* The other is a counter of updaters. Before an update happens
|
|
* the update partition of the counter is incremented. This will
|
|
* allow the updater to update the counter atomically.
|
|
*
|
|
* The counter is 20 bits, and the state data is 12.
|
|
*/
|
|
#define RB_WRITE_MASK 0xfffff
|
|
#define RB_WRITE_INTCNT (1 << 20)
|
|
|
|
static void rb_init_page(struct buffer_data_page *bpage)
|
|
{
|
|
local_set(&bpage->commit, 0);
|
|
}
|
|
|
|
static __always_inline unsigned int rb_page_commit(struct buffer_page *bpage)
|
|
{
|
|
return local_read(&bpage->page->commit);
|
|
}
|
|
|
|
static void free_buffer_page(struct buffer_page *bpage)
|
|
{
|
|
free_pages((unsigned long)bpage->page, bpage->order);
|
|
kfree(bpage);
|
|
}
|
|
|
|
/*
|
|
* We need to fit the time_stamp delta into 27 bits.
|
|
*/
|
|
static inline bool test_time_stamp(u64 delta)
|
|
{
|
|
return !!(delta & TS_DELTA_TEST);
|
|
}
|
|
|
|
struct rb_irq_work {
|
|
struct irq_work work;
|
|
wait_queue_head_t waiters;
|
|
wait_queue_head_t full_waiters;
|
|
atomic_t seq;
|
|
bool waiters_pending;
|
|
bool full_waiters_pending;
|
|
bool wakeup_full;
|
|
};
|
|
|
|
/*
|
|
* Structure to hold event state and handle nested events.
|
|
*/
|
|
struct rb_event_info {
|
|
u64 ts;
|
|
u64 delta;
|
|
u64 before;
|
|
u64 after;
|
|
unsigned long length;
|
|
struct buffer_page *tail_page;
|
|
int add_timestamp;
|
|
};
|
|
|
|
/*
|
|
* Used for the add_timestamp
|
|
* NONE
|
|
* EXTEND - wants a time extend
|
|
* ABSOLUTE - the buffer requests all events to have absolute time stamps
|
|
* FORCE - force a full time stamp.
|
|
*/
|
|
enum {
|
|
RB_ADD_STAMP_NONE = 0,
|
|
RB_ADD_STAMP_EXTEND = BIT(1),
|
|
RB_ADD_STAMP_ABSOLUTE = BIT(2),
|
|
RB_ADD_STAMP_FORCE = BIT(3)
|
|
};
|
|
/*
|
|
* Used for which event context the event is in.
|
|
* TRANSITION = 0
|
|
* NMI = 1
|
|
* IRQ = 2
|
|
* SOFTIRQ = 3
|
|
* NORMAL = 4
|
|
*
|
|
* See trace_recursive_lock() comment below for more details.
|
|
*/
|
|
enum {
|
|
RB_CTX_TRANSITION,
|
|
RB_CTX_NMI,
|
|
RB_CTX_IRQ,
|
|
RB_CTX_SOFTIRQ,
|
|
RB_CTX_NORMAL,
|
|
RB_CTX_MAX
|
|
};
|
|
|
|
struct rb_time_struct {
|
|
local64_t time;
|
|
};
|
|
typedef struct rb_time_struct rb_time_t;
|
|
|
|
#define MAX_NEST 5
|
|
|
|
/*
|
|
* head_page == tail_page && head == tail then buffer is empty.
|
|
*/
|
|
struct ring_buffer_per_cpu {
|
|
int cpu;
|
|
atomic_t record_disabled;
|
|
atomic_t resize_disabled;
|
|
struct trace_buffer *buffer;
|
|
raw_spinlock_t reader_lock; /* serialize readers */
|
|
arch_spinlock_t lock;
|
|
struct lock_class_key lock_key;
|
|
struct buffer_data_page *free_page;
|
|
unsigned long nr_pages;
|
|
unsigned int current_context;
|
|
struct list_head *pages;
|
|
struct buffer_page *head_page; /* read from head */
|
|
struct buffer_page *tail_page; /* write to tail */
|
|
struct buffer_page *commit_page; /* committed pages */
|
|
struct buffer_page *reader_page;
|
|
unsigned long lost_events;
|
|
unsigned long last_overrun;
|
|
unsigned long nest;
|
|
local_t entries_bytes;
|
|
local_t entries;
|
|
local_t overrun;
|
|
local_t commit_overrun;
|
|
local_t dropped_events;
|
|
local_t committing;
|
|
local_t commits;
|
|
local_t pages_touched;
|
|
local_t pages_lost;
|
|
local_t pages_read;
|
|
long last_pages_touch;
|
|
size_t shortest_full;
|
|
unsigned long read;
|
|
unsigned long read_bytes;
|
|
rb_time_t write_stamp;
|
|
rb_time_t before_stamp;
|
|
u64 event_stamp[MAX_NEST];
|
|
u64 read_stamp;
|
|
/* pages removed since last reset */
|
|
unsigned long pages_removed;
|
|
|
|
unsigned int mapped;
|
|
struct mutex mapping_lock;
|
|
unsigned long *subbuf_ids; /* ID to subbuf VA */
|
|
struct trace_buffer_meta *meta_page;
|
|
|
|
/* ring buffer pages to update, > 0 to add, < 0 to remove */
|
|
long nr_pages_to_update;
|
|
struct list_head new_pages; /* new pages to add */
|
|
struct work_struct update_pages_work;
|
|
struct completion update_done;
|
|
|
|
struct rb_irq_work irq_work;
|
|
};
|
|
|
|
struct trace_buffer {
|
|
unsigned flags;
|
|
int cpus;
|
|
atomic_t record_disabled;
|
|
atomic_t resizing;
|
|
cpumask_var_t cpumask;
|
|
|
|
struct lock_class_key *reader_lock_key;
|
|
|
|
struct mutex mutex;
|
|
|
|
struct ring_buffer_per_cpu **buffers;
|
|
|
|
struct hlist_node node;
|
|
u64 (*clock)(void);
|
|
|
|
struct rb_irq_work irq_work;
|
|
bool time_stamp_abs;
|
|
|
|
unsigned int subbuf_size;
|
|
unsigned int subbuf_order;
|
|
unsigned int max_data_size;
|
|
};
|
|
|
|
struct ring_buffer_iter {
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
unsigned long head;
|
|
unsigned long next_event;
|
|
struct buffer_page *head_page;
|
|
struct buffer_page *cache_reader_page;
|
|
unsigned long cache_read;
|
|
unsigned long cache_pages_removed;
|
|
u64 read_stamp;
|
|
u64 page_stamp;
|
|
struct ring_buffer_event *event;
|
|
size_t event_size;
|
|
int missed_events;
|
|
};
|
|
|
|
int ring_buffer_print_page_header(struct trace_buffer *buffer, struct trace_seq *s)
|
|
{
|
|
struct buffer_data_page field;
|
|
|
|
trace_seq_printf(s, "\tfield: u64 timestamp;\t"
|
|
"offset:0;\tsize:%u;\tsigned:%u;\n",
|
|
(unsigned int)sizeof(field.time_stamp),
|
|
(unsigned int)is_signed_type(u64));
|
|
|
|
trace_seq_printf(s, "\tfield: local_t commit;\t"
|
|
"offset:%u;\tsize:%u;\tsigned:%u;\n",
|
|
(unsigned int)offsetof(typeof(field), commit),
|
|
(unsigned int)sizeof(field.commit),
|
|
(unsigned int)is_signed_type(long));
|
|
|
|
trace_seq_printf(s, "\tfield: int overwrite;\t"
|
|
"offset:%u;\tsize:%u;\tsigned:%u;\n",
|
|
(unsigned int)offsetof(typeof(field), commit),
|
|
1,
|
|
(unsigned int)is_signed_type(long));
|
|
|
|
trace_seq_printf(s, "\tfield: char data;\t"
|
|
"offset:%u;\tsize:%u;\tsigned:%u;\n",
|
|
(unsigned int)offsetof(typeof(field), data),
|
|
(unsigned int)buffer->subbuf_size,
|
|
(unsigned int)is_signed_type(char));
|
|
|
|
return !trace_seq_has_overflowed(s);
|
|
}
|
|
|
|
static inline void rb_time_read(rb_time_t *t, u64 *ret)
|
|
{
|
|
*ret = local64_read(&t->time);
|
|
}
|
|
static void rb_time_set(rb_time_t *t, u64 val)
|
|
{
|
|
local64_set(&t->time, val);
|
|
}
|
|
|
|
/*
|
|
* Enable this to make sure that the event passed to
|
|
* ring_buffer_event_time_stamp() is not committed and also
|
|
* is on the buffer that it passed in.
|
|
*/
|
|
//#define RB_VERIFY_EVENT
|
|
#ifdef RB_VERIFY_EVENT
|
|
static struct list_head *rb_list_head(struct list_head *list);
|
|
static void verify_event(struct ring_buffer_per_cpu *cpu_buffer,
|
|
void *event)
|
|
{
|
|
struct buffer_page *page = cpu_buffer->commit_page;
|
|
struct buffer_page *tail_page = READ_ONCE(cpu_buffer->tail_page);
|
|
struct list_head *next;
|
|
long commit, write;
|
|
unsigned long addr = (unsigned long)event;
|
|
bool done = false;
|
|
int stop = 0;
|
|
|
|
/* Make sure the event exists and is not committed yet */
|
|
do {
|
|
if (page == tail_page || WARN_ON_ONCE(stop++ > 100))
|
|
done = true;
|
|
commit = local_read(&page->page->commit);
|
|
write = local_read(&page->write);
|
|
if (addr >= (unsigned long)&page->page->data[commit] &&
|
|
addr < (unsigned long)&page->page->data[write])
|
|
return;
|
|
|
|
next = rb_list_head(page->list.next);
|
|
page = list_entry(next, struct buffer_page, list);
|
|
} while (!done);
|
|
WARN_ON_ONCE(1);
|
|
}
|
|
#else
|
|
static inline void verify_event(struct ring_buffer_per_cpu *cpu_buffer,
|
|
void *event)
|
|
{
|
|
}
|
|
#endif
|
|
|
|
/*
|
|
* The absolute time stamp drops the 5 MSBs and some clocks may
|
|
* require them. The rb_fix_abs_ts() will take a previous full
|
|
* time stamp, and add the 5 MSB of that time stamp on to the
|
|
* saved absolute time stamp. Then they are compared in case of
|
|
* the unlikely event that the latest time stamp incremented
|
|
* the 5 MSB.
|
|
*/
|
|
static inline u64 rb_fix_abs_ts(u64 abs, u64 save_ts)
|
|
{
|
|
if (save_ts & TS_MSB) {
|
|
abs |= save_ts & TS_MSB;
|
|
/* Check for overflow */
|
|
if (unlikely(abs < save_ts))
|
|
abs += 1ULL << 59;
|
|
}
|
|
return abs;
|
|
}
|
|
|
|
static inline u64 rb_time_stamp(struct trace_buffer *buffer);
|
|
|
|
/**
|
|
* ring_buffer_event_time_stamp - return the event's current time stamp
|
|
* @buffer: The buffer that the event is on
|
|
* @event: the event to get the time stamp of
|
|
*
|
|
* Note, this must be called after @event is reserved, and before it is
|
|
* committed to the ring buffer. And must be called from the same
|
|
* context where the event was reserved (normal, softirq, irq, etc).
|
|
*
|
|
* Returns the time stamp associated with the current event.
|
|
* If the event has an extended time stamp, then that is used as
|
|
* the time stamp to return.
|
|
* In the highly unlikely case that the event was nested more than
|
|
* the max nesting, then the write_stamp of the buffer is returned,
|
|
* otherwise current time is returned, but that really neither of
|
|
* the last two cases should ever happen.
|
|
*/
|
|
u64 ring_buffer_event_time_stamp(struct trace_buffer *buffer,
|
|
struct ring_buffer_event *event)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[smp_processor_id()];
|
|
unsigned int nest;
|
|
u64 ts;
|
|
|
|
/* If the event includes an absolute time, then just use that */
|
|
if (event->type_len == RINGBUF_TYPE_TIME_STAMP) {
|
|
ts = rb_event_time_stamp(event);
|
|
return rb_fix_abs_ts(ts, cpu_buffer->tail_page->page->time_stamp);
|
|
}
|
|
|
|
nest = local_read(&cpu_buffer->committing);
|
|
verify_event(cpu_buffer, event);
|
|
if (WARN_ON_ONCE(!nest))
|
|
goto fail;
|
|
|
|
/* Read the current saved nesting level time stamp */
|
|
if (likely(--nest < MAX_NEST))
|
|
return cpu_buffer->event_stamp[nest];
|
|
|
|
/* Shouldn't happen, warn if it does */
|
|
WARN_ONCE(1, "nest (%d) greater than max", nest);
|
|
|
|
fail:
|
|
rb_time_read(&cpu_buffer->write_stamp, &ts);
|
|
|
|
return ts;
|
|
}
|
|
|
|
/**
|
|
* ring_buffer_nr_pages - get the number of buffer pages in the ring buffer
|
|
* @buffer: The ring_buffer to get the number of pages from
|
|
* @cpu: The cpu of the ring_buffer to get the number of pages from
|
|
*
|
|
* Returns the number of pages used by a per_cpu buffer of the ring buffer.
|
|
*/
|
|
size_t ring_buffer_nr_pages(struct trace_buffer *buffer, int cpu)
|
|
{
|
|
return buffer->buffers[cpu]->nr_pages;
|
|
}
|
|
|
|
/**
|
|
* ring_buffer_nr_dirty_pages - get the number of used pages in the ring buffer
|
|
* @buffer: The ring_buffer to get the number of pages from
|
|
* @cpu: The cpu of the ring_buffer to get the number of pages from
|
|
*
|
|
* Returns the number of pages that have content in the ring buffer.
|
|
*/
|
|
size_t ring_buffer_nr_dirty_pages(struct trace_buffer *buffer, int cpu)
|
|
{
|
|
size_t read;
|
|
size_t lost;
|
|
size_t cnt;
|
|
|
|
read = local_read(&buffer->buffers[cpu]->pages_read);
|
|
lost = local_read(&buffer->buffers[cpu]->pages_lost);
|
|
cnt = local_read(&buffer->buffers[cpu]->pages_touched);
|
|
|
|
if (WARN_ON_ONCE(cnt < lost))
|
|
return 0;
|
|
|
|
cnt -= lost;
|
|
|
|
/* The reader can read an empty page, but not more than that */
|
|
if (cnt < read) {
|
|
WARN_ON_ONCE(read > cnt + 1);
|
|
return 0;
|
|
}
|
|
|
|
return cnt - read;
|
|
}
|
|
|
|
static __always_inline bool full_hit(struct trace_buffer *buffer, int cpu, int full)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
|
|
size_t nr_pages;
|
|
size_t dirty;
|
|
|
|
nr_pages = cpu_buffer->nr_pages;
|
|
if (!nr_pages || !full)
|
|
return true;
|
|
|
|
/*
|
|
* Add one as dirty will never equal nr_pages, as the sub-buffer
|
|
* that the writer is on is not counted as dirty.
|
|
* This is needed if "buffer_percent" is set to 100.
|
|
*/
|
|
dirty = ring_buffer_nr_dirty_pages(buffer, cpu) + 1;
|
|
|
|
return (dirty * 100) >= (full * nr_pages);
|
|
}
|
|
|
|
/*
|
|
* rb_wake_up_waiters - wake up tasks waiting for ring buffer input
|
|
*
|
|
* Schedules a delayed work to wake up any task that is blocked on the
|
|
* ring buffer waiters queue.
|
|
*/
|
|
static void rb_wake_up_waiters(struct irq_work *work)
|
|
{
|
|
struct rb_irq_work *rbwork = container_of(work, struct rb_irq_work, work);
|
|
|
|
/* For waiters waiting for the first wake up */
|
|
(void)atomic_fetch_inc_release(&rbwork->seq);
|
|
|
|
wake_up_all(&rbwork->waiters);
|
|
if (rbwork->full_waiters_pending || rbwork->wakeup_full) {
|
|
/* Only cpu_buffer sets the above flags */
|
|
struct ring_buffer_per_cpu *cpu_buffer =
|
|
container_of(rbwork, struct ring_buffer_per_cpu, irq_work);
|
|
|
|
/* Called from interrupt context */
|
|
raw_spin_lock(&cpu_buffer->reader_lock);
|
|
rbwork->wakeup_full = false;
|
|
rbwork->full_waiters_pending = false;
|
|
|
|
/* Waking up all waiters, they will reset the shortest full */
|
|
cpu_buffer->shortest_full = 0;
|
|
raw_spin_unlock(&cpu_buffer->reader_lock);
|
|
|
|
wake_up_all(&rbwork->full_waiters);
|
|
}
|
|
}
|
|
|
|
/**
|
|
* ring_buffer_wake_waiters - wake up any waiters on this ring buffer
|
|
* @buffer: The ring buffer to wake waiters on
|
|
* @cpu: The CPU buffer to wake waiters on
|
|
*
|
|
* In the case of a file that represents a ring buffer is closing,
|
|
* it is prudent to wake up any waiters that are on this.
|
|
*/
|
|
void ring_buffer_wake_waiters(struct trace_buffer *buffer, int cpu)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
struct rb_irq_work *rbwork;
|
|
|
|
if (!buffer)
|
|
return;
|
|
|
|
if (cpu == RING_BUFFER_ALL_CPUS) {
|
|
|
|
/* Wake up individual ones too. One level recursion */
|
|
for_each_buffer_cpu(buffer, cpu)
|
|
ring_buffer_wake_waiters(buffer, cpu);
|
|
|
|
rbwork = &buffer->irq_work;
|
|
} else {
|
|
if (WARN_ON_ONCE(!buffer->buffers))
|
|
return;
|
|
if (WARN_ON_ONCE(cpu >= nr_cpu_ids))
|
|
return;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
/* The CPU buffer may not have been initialized yet */
|
|
if (!cpu_buffer)
|
|
return;
|
|
rbwork = &cpu_buffer->irq_work;
|
|
}
|
|
|
|
/* This can be called in any context */
|
|
irq_work_queue(&rbwork->work);
|
|
}
|
|
|
|
static bool rb_watermark_hit(struct trace_buffer *buffer, int cpu, int full)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
bool ret = false;
|
|
|
|
/* Reads of all CPUs always waits for any data */
|
|
if (cpu == RING_BUFFER_ALL_CPUS)
|
|
return !ring_buffer_empty(buffer);
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
|
|
if (!ring_buffer_empty_cpu(buffer, cpu)) {
|
|
unsigned long flags;
|
|
bool pagebusy;
|
|
|
|
if (!full)
|
|
return true;
|
|
|
|
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
|
|
pagebusy = cpu_buffer->reader_page == cpu_buffer->commit_page;
|
|
ret = !pagebusy && full_hit(buffer, cpu, full);
|
|
|
|
if (!ret && (!cpu_buffer->shortest_full ||
|
|
cpu_buffer->shortest_full > full)) {
|
|
cpu_buffer->shortest_full = full;
|
|
}
|
|
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
|
|
}
|
|
return ret;
|
|
}
|
|
|
|
static inline bool
|
|
rb_wait_cond(struct rb_irq_work *rbwork, struct trace_buffer *buffer,
|
|
int cpu, int full, ring_buffer_cond_fn cond, void *data)
|
|
{
|
|
if (rb_watermark_hit(buffer, cpu, full))
|
|
return true;
|
|
|
|
if (cond(data))
|
|
return true;
|
|
|
|
/*
|
|
* The events can happen in critical sections where
|
|
* checking a work queue can cause deadlocks.
|
|
* After adding a task to the queue, this flag is set
|
|
* only to notify events to try to wake up the queue
|
|
* using irq_work.
|
|
*
|
|
* We don't clear it even if the buffer is no longer
|
|
* empty. The flag only causes the next event to run
|
|
* irq_work to do the work queue wake up. The worse
|
|
* that can happen if we race with !trace_empty() is that
|
|
* an event will cause an irq_work to try to wake up
|
|
* an empty queue.
|
|
*
|
|
* There's no reason to protect this flag either, as
|
|
* the work queue and irq_work logic will do the necessary
|
|
* synchronization for the wake ups. The only thing
|
|
* that is necessary is that the wake up happens after
|
|
* a task has been queued. It's OK for spurious wake ups.
|
|
*/
|
|
if (full)
|
|
rbwork->full_waiters_pending = true;
|
|
else
|
|
rbwork->waiters_pending = true;
|
|
|
|
return false;
|
|
}
|
|
|
|
struct rb_wait_data {
|
|
struct rb_irq_work *irq_work;
|
|
int seq;
|
|
};
|
|
|
|
/*
|
|
* The default wait condition for ring_buffer_wait() is to just to exit the
|
|
* wait loop the first time it is woken up.
|
|
*/
|
|
static bool rb_wait_once(void *data)
|
|
{
|
|
struct rb_wait_data *rdata = data;
|
|
struct rb_irq_work *rbwork = rdata->irq_work;
|
|
|
|
return atomic_read_acquire(&rbwork->seq) != rdata->seq;
|
|
}
|
|
|
|
/**
|
|
* ring_buffer_wait - wait for input to the ring buffer
|
|
* @buffer: buffer to wait on
|
|
* @cpu: the cpu buffer to wait on
|
|
* @full: wait until the percentage of pages are available, if @cpu != RING_BUFFER_ALL_CPUS
|
|
* @cond: condition function to break out of wait (NULL to run once)
|
|
* @data: the data to pass to @cond.
|
|
*
|
|
* If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
|
|
* as data is added to any of the @buffer's cpu buffers. Otherwise
|
|
* it will wait for data to be added to a specific cpu buffer.
|
|
*/
|
|
int ring_buffer_wait(struct trace_buffer *buffer, int cpu, int full,
|
|
ring_buffer_cond_fn cond, void *data)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
struct wait_queue_head *waitq;
|
|
struct rb_irq_work *rbwork;
|
|
struct rb_wait_data rdata;
|
|
int ret = 0;
|
|
|
|
/*
|
|
* Depending on what the caller is waiting for, either any
|
|
* data in any cpu buffer, or a specific buffer, put the
|
|
* caller on the appropriate wait queue.
|
|
*/
|
|
if (cpu == RING_BUFFER_ALL_CPUS) {
|
|
rbwork = &buffer->irq_work;
|
|
/* Full only makes sense on per cpu reads */
|
|
full = 0;
|
|
} else {
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
return -ENODEV;
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
rbwork = &cpu_buffer->irq_work;
|
|
}
|
|
|
|
if (full)
|
|
waitq = &rbwork->full_waiters;
|
|
else
|
|
waitq = &rbwork->waiters;
|
|
|
|
/* Set up to exit loop as soon as it is woken */
|
|
if (!cond) {
|
|
cond = rb_wait_once;
|
|
rdata.irq_work = rbwork;
|
|
rdata.seq = atomic_read_acquire(&rbwork->seq);
|
|
data = &rdata;
|
|
}
|
|
|
|
ret = wait_event_interruptible((*waitq),
|
|
rb_wait_cond(rbwork, buffer, cpu, full, cond, data));
|
|
|
|
return ret;
|
|
}
|
|
|
|
/**
|
|
* ring_buffer_poll_wait - poll on buffer input
|
|
* @buffer: buffer to wait on
|
|
* @cpu: the cpu buffer to wait on
|
|
* @filp: the file descriptor
|
|
* @poll_table: The poll descriptor
|
|
* @full: wait until the percentage of pages are available, if @cpu != RING_BUFFER_ALL_CPUS
|
|
*
|
|
* If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon
|
|
* as data is added to any of the @buffer's cpu buffers. Otherwise
|
|
* it will wait for data to be added to a specific cpu buffer.
|
|
*
|
|
* Returns EPOLLIN | EPOLLRDNORM if data exists in the buffers,
|
|
* zero otherwise.
|
|
*/
|
|
__poll_t ring_buffer_poll_wait(struct trace_buffer *buffer, int cpu,
|
|
struct file *filp, poll_table *poll_table, int full)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
struct rb_irq_work *rbwork;
|
|
|
|
if (cpu == RING_BUFFER_ALL_CPUS) {
|
|
rbwork = &buffer->irq_work;
|
|
full = 0;
|
|
} else {
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
return EPOLLERR;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
rbwork = &cpu_buffer->irq_work;
|
|
}
|
|
|
|
if (full) {
|
|
poll_wait(filp, &rbwork->full_waiters, poll_table);
|
|
|
|
if (rb_watermark_hit(buffer, cpu, full))
|
|
return EPOLLIN | EPOLLRDNORM;
|
|
/*
|
|
* Only allow full_waiters_pending update to be seen after
|
|
* the shortest_full is set (in rb_watermark_hit). If the
|
|
* writer sees the full_waiters_pending flag set, it will
|
|
* compare the amount in the ring buffer to shortest_full.
|
|
* If the amount in the ring buffer is greater than the
|
|
* shortest_full percent, it will call the irq_work handler
|
|
* to wake up this list. The irq_handler will reset shortest_full
|
|
* back to zero. That's done under the reader_lock, but
|
|
* the below smp_mb() makes sure that the update to
|
|
* full_waiters_pending doesn't leak up into the above.
|
|
*/
|
|
smp_mb();
|
|
rbwork->full_waiters_pending = true;
|
|
return 0;
|
|
}
|
|
|
|
poll_wait(filp, &rbwork->waiters, poll_table);
|
|
rbwork->waiters_pending = true;
|
|
|
|
/*
|
|
* There's a tight race between setting the waiters_pending and
|
|
* checking if the ring buffer is empty. Once the waiters_pending bit
|
|
* is set, the next event will wake the task up, but we can get stuck
|
|
* if there's only a single event in.
|
|
*
|
|
* FIXME: Ideally, we need a memory barrier on the writer side as well,
|
|
* but adding a memory barrier to all events will cause too much of a
|
|
* performance hit in the fast path. We only need a memory barrier when
|
|
* the buffer goes from empty to having content. But as this race is
|
|
* extremely small, and it's not a problem if another event comes in, we
|
|
* will fix it later.
|
|
*/
|
|
smp_mb();
|
|
|
|
if ((cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer)) ||
|
|
(cpu != RING_BUFFER_ALL_CPUS && !ring_buffer_empty_cpu(buffer, cpu)))
|
|
return EPOLLIN | EPOLLRDNORM;
|
|
return 0;
|
|
}
|
|
|
|
/* buffer may be either ring_buffer or ring_buffer_per_cpu */
|
|
#define RB_WARN_ON(b, cond) \
|
|
({ \
|
|
int _____ret = unlikely(cond); \
|
|
if (_____ret) { \
|
|
if (__same_type(*(b), struct ring_buffer_per_cpu)) { \
|
|
struct ring_buffer_per_cpu *__b = \
|
|
(void *)b; \
|
|
atomic_inc(&__b->buffer->record_disabled); \
|
|
} else \
|
|
atomic_inc(&b->record_disabled); \
|
|
WARN_ON(1); \
|
|
} \
|
|
_____ret; \
|
|
})
|
|
|
|
/* Up this if you want to test the TIME_EXTENTS and normalization */
|
|
#define DEBUG_SHIFT 0
|
|
|
|
static inline u64 rb_time_stamp(struct trace_buffer *buffer)
|
|
{
|
|
u64 ts;
|
|
|
|
/* Skip retpolines :-( */
|
|
if (IS_ENABLED(CONFIG_MITIGATION_RETPOLINE) && likely(buffer->clock == trace_clock_local))
|
|
ts = trace_clock_local();
|
|
else
|
|
ts = buffer->clock();
|
|
|
|
/* shift to debug/test normalization and TIME_EXTENTS */
|
|
return ts << DEBUG_SHIFT;
|
|
}
|
|
|
|
u64 ring_buffer_time_stamp(struct trace_buffer *buffer)
|
|
{
|
|
u64 time;
|
|
|
|
preempt_disable_notrace();
|
|
time = rb_time_stamp(buffer);
|
|
preempt_enable_notrace();
|
|
|
|
return time;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_time_stamp);
|
|
|
|
void ring_buffer_normalize_time_stamp(struct trace_buffer *buffer,
|
|
int cpu, u64 *ts)
|
|
{
|
|
/* Just stupid testing the normalize function and deltas */
|
|
*ts >>= DEBUG_SHIFT;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp);
|
|
|
|
/*
|
|
* Making the ring buffer lockless makes things tricky.
|
|
* Although writes only happen on the CPU that they are on,
|
|
* and they only need to worry about interrupts. Reads can
|
|
* happen on any CPU.
|
|
*
|
|
* The reader page is always off the ring buffer, but when the
|
|
* reader finishes with a page, it needs to swap its page with
|
|
* a new one from the buffer. The reader needs to take from
|
|
* the head (writes go to the tail). But if a writer is in overwrite
|
|
* mode and wraps, it must push the head page forward.
|
|
*
|
|
* Here lies the problem.
|
|
*
|
|
* The reader must be careful to replace only the head page, and
|
|
* not another one. As described at the top of the file in the
|
|
* ASCII art, the reader sets its old page to point to the next
|
|
* page after head. It then sets the page after head to point to
|
|
* the old reader page. But if the writer moves the head page
|
|
* during this operation, the reader could end up with the tail.
|
|
*
|
|
* We use cmpxchg to help prevent this race. We also do something
|
|
* special with the page before head. We set the LSB to 1.
|
|
*
|
|
* When the writer must push the page forward, it will clear the
|
|
* bit that points to the head page, move the head, and then set
|
|
* the bit that points to the new head page.
|
|
*
|
|
* We also don't want an interrupt coming in and moving the head
|
|
* page on another writer. Thus we use the second LSB to catch
|
|
* that too. Thus:
|
|
*
|
|
* head->list->prev->next bit 1 bit 0
|
|
* ------- -------
|
|
* Normal page 0 0
|
|
* Points to head page 0 1
|
|
* New head page 1 0
|
|
*
|
|
* Note we can not trust the prev pointer of the head page, because:
|
|
*
|
|
* +----+ +-----+ +-----+
|
|
* | |------>| T |---X--->| N |
|
|
* | |<------| | | |
|
|
* +----+ +-----+ +-----+
|
|
* ^ ^ |
|
|
* | +-----+ | |
|
|
* +----------| R |----------+ |
|
|
* | |<-----------+
|
|
* +-----+
|
|
*
|
|
* Key: ---X--> HEAD flag set in pointer
|
|
* T Tail page
|
|
* R Reader page
|
|
* N Next page
|
|
*
|
|
* (see __rb_reserve_next() to see where this happens)
|
|
*
|
|
* What the above shows is that the reader just swapped out
|
|
* the reader page with a page in the buffer, but before it
|
|
* could make the new header point back to the new page added
|
|
* it was preempted by a writer. The writer moved forward onto
|
|
* the new page added by the reader and is about to move forward
|
|
* again.
|
|
*
|
|
* You can see, it is legitimate for the previous pointer of
|
|
* the head (or any page) not to point back to itself. But only
|
|
* temporarily.
|
|
*/
|
|
|
|
#define RB_PAGE_NORMAL 0UL
|
|
#define RB_PAGE_HEAD 1UL
|
|
#define RB_PAGE_UPDATE 2UL
|
|
|
|
|
|
#define RB_FLAG_MASK 3UL
|
|
|
|
/* PAGE_MOVED is not part of the mask */
|
|
#define RB_PAGE_MOVED 4UL
|
|
|
|
/*
|
|
* rb_list_head - remove any bit
|
|
*/
|
|
static struct list_head *rb_list_head(struct list_head *list)
|
|
{
|
|
unsigned long val = (unsigned long)list;
|
|
|
|
return (struct list_head *)(val & ~RB_FLAG_MASK);
|
|
}
|
|
|
|
/*
|
|
* rb_is_head_page - test if the given page is the head page
|
|
*
|
|
* Because the reader may move the head_page pointer, we can
|
|
* not trust what the head page is (it may be pointing to
|
|
* the reader page). But if the next page is a header page,
|
|
* its flags will be non zero.
|
|
*/
|
|
static inline int
|
|
rb_is_head_page(struct buffer_page *page, struct list_head *list)
|
|
{
|
|
unsigned long val;
|
|
|
|
val = (unsigned long)list->next;
|
|
|
|
if ((val & ~RB_FLAG_MASK) != (unsigned long)&page->list)
|
|
return RB_PAGE_MOVED;
|
|
|
|
return val & RB_FLAG_MASK;
|
|
}
|
|
|
|
/*
|
|
* rb_is_reader_page
|
|
*
|
|
* The unique thing about the reader page, is that, if the
|
|
* writer is ever on it, the previous pointer never points
|
|
* back to the reader page.
|
|
*/
|
|
static bool rb_is_reader_page(struct buffer_page *page)
|
|
{
|
|
struct list_head *list = page->list.prev;
|
|
|
|
return rb_list_head(list->next) != &page->list;
|
|
}
|
|
|
|
/*
|
|
* rb_set_list_to_head - set a list_head to be pointing to head.
|
|
*/
|
|
static void rb_set_list_to_head(struct list_head *list)
|
|
{
|
|
unsigned long *ptr;
|
|
|
|
ptr = (unsigned long *)&list->next;
|
|
*ptr |= RB_PAGE_HEAD;
|
|
*ptr &= ~RB_PAGE_UPDATE;
|
|
}
|
|
|
|
/*
|
|
* rb_head_page_activate - sets up head page
|
|
*/
|
|
static void rb_head_page_activate(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
struct buffer_page *head;
|
|
|
|
head = cpu_buffer->head_page;
|
|
if (!head)
|
|
return;
|
|
|
|
/*
|
|
* Set the previous list pointer to have the HEAD flag.
|
|
*/
|
|
rb_set_list_to_head(head->list.prev);
|
|
}
|
|
|
|
static void rb_list_head_clear(struct list_head *list)
|
|
{
|
|
unsigned long *ptr = (unsigned long *)&list->next;
|
|
|
|
*ptr &= ~RB_FLAG_MASK;
|
|
}
|
|
|
|
/*
|
|
* rb_head_page_deactivate - clears head page ptr (for free list)
|
|
*/
|
|
static void
|
|
rb_head_page_deactivate(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
struct list_head *hd;
|
|
|
|
/* Go through the whole list and clear any pointers found. */
|
|
rb_list_head_clear(cpu_buffer->pages);
|
|
|
|
list_for_each(hd, cpu_buffer->pages)
|
|
rb_list_head_clear(hd);
|
|
}
|
|
|
|
static int rb_head_page_set(struct ring_buffer_per_cpu *cpu_buffer,
|
|
struct buffer_page *head,
|
|
struct buffer_page *prev,
|
|
int old_flag, int new_flag)
|
|
{
|
|
struct list_head *list;
|
|
unsigned long val = (unsigned long)&head->list;
|
|
unsigned long ret;
|
|
|
|
list = &prev->list;
|
|
|
|
val &= ~RB_FLAG_MASK;
|
|
|
|
ret = cmpxchg((unsigned long *)&list->next,
|
|
val | old_flag, val | new_flag);
|
|
|
|
/* check if the reader took the page */
|
|
if ((ret & ~RB_FLAG_MASK) != val)
|
|
return RB_PAGE_MOVED;
|
|
|
|
return ret & RB_FLAG_MASK;
|
|
}
|
|
|
|
static int rb_head_page_set_update(struct ring_buffer_per_cpu *cpu_buffer,
|
|
struct buffer_page *head,
|
|
struct buffer_page *prev,
|
|
int old_flag)
|
|
{
|
|
return rb_head_page_set(cpu_buffer, head, prev,
|
|
old_flag, RB_PAGE_UPDATE);
|
|
}
|
|
|
|
static int rb_head_page_set_head(struct ring_buffer_per_cpu *cpu_buffer,
|
|
struct buffer_page *head,
|
|
struct buffer_page *prev,
|
|
int old_flag)
|
|
{
|
|
return rb_head_page_set(cpu_buffer, head, prev,
|
|
old_flag, RB_PAGE_HEAD);
|
|
}
|
|
|
|
static int rb_head_page_set_normal(struct ring_buffer_per_cpu *cpu_buffer,
|
|
struct buffer_page *head,
|
|
struct buffer_page *prev,
|
|
int old_flag)
|
|
{
|
|
return rb_head_page_set(cpu_buffer, head, prev,
|
|
old_flag, RB_PAGE_NORMAL);
|
|
}
|
|
|
|
static inline void rb_inc_page(struct buffer_page **bpage)
|
|
{
|
|
struct list_head *p = rb_list_head((*bpage)->list.next);
|
|
|
|
*bpage = list_entry(p, struct buffer_page, list);
|
|
}
|
|
|
|
static struct buffer_page *
|
|
rb_set_head_page(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
struct buffer_page *head;
|
|
struct buffer_page *page;
|
|
struct list_head *list;
|
|
int i;
|
|
|
|
if (RB_WARN_ON(cpu_buffer, !cpu_buffer->head_page))
|
|
return NULL;
|
|
|
|
/* sanity check */
|
|
list = cpu_buffer->pages;
|
|
if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev->next) != list))
|
|
return NULL;
|
|
|
|
page = head = cpu_buffer->head_page;
|
|
/*
|
|
* It is possible that the writer moves the header behind
|
|
* where we started, and we miss in one loop.
|
|
* A second loop should grab the header, but we'll do
|
|
* three loops just because I'm paranoid.
|
|
*/
|
|
for (i = 0; i < 3; i++) {
|
|
do {
|
|
if (rb_is_head_page(page, page->list.prev)) {
|
|
cpu_buffer->head_page = page;
|
|
return page;
|
|
}
|
|
rb_inc_page(&page);
|
|
} while (page != head);
|
|
}
|
|
|
|
RB_WARN_ON(cpu_buffer, 1);
|
|
|
|
return NULL;
|
|
}
|
|
|
|
static bool rb_head_page_replace(struct buffer_page *old,
|
|
struct buffer_page *new)
|
|
{
|
|
unsigned long *ptr = (unsigned long *)&old->list.prev->next;
|
|
unsigned long val;
|
|
|
|
val = *ptr & ~RB_FLAG_MASK;
|
|
val |= RB_PAGE_HEAD;
|
|
|
|
return try_cmpxchg(ptr, &val, (unsigned long)&new->list);
|
|
}
|
|
|
|
/*
|
|
* rb_tail_page_update - move the tail page forward
|
|
*/
|
|
static void rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer,
|
|
struct buffer_page *tail_page,
|
|
struct buffer_page *next_page)
|
|
{
|
|
unsigned long old_entries;
|
|
unsigned long old_write;
|
|
|
|
/*
|
|
* The tail page now needs to be moved forward.
|
|
*
|
|
* We need to reset the tail page, but without messing
|
|
* with possible erasing of data brought in by interrupts
|
|
* that have moved the tail page and are currently on it.
|
|
*
|
|
* We add a counter to the write field to denote this.
|
|
*/
|
|
old_write = local_add_return(RB_WRITE_INTCNT, &next_page->write);
|
|
old_entries = local_add_return(RB_WRITE_INTCNT, &next_page->entries);
|
|
|
|
/*
|
|
* Just make sure we have seen our old_write and synchronize
|
|
* with any interrupts that come in.
|
|
*/
|
|
barrier();
|
|
|
|
/*
|
|
* If the tail page is still the same as what we think
|
|
* it is, then it is up to us to update the tail
|
|
* pointer.
|
|
*/
|
|
if (tail_page == READ_ONCE(cpu_buffer->tail_page)) {
|
|
/* Zero the write counter */
|
|
unsigned long val = old_write & ~RB_WRITE_MASK;
|
|
unsigned long eval = old_entries & ~RB_WRITE_MASK;
|
|
|
|
/*
|
|
* This will only succeed if an interrupt did
|
|
* not come in and change it. In which case, we
|
|
* do not want to modify it.
|
|
*
|
|
* We add (void) to let the compiler know that we do not care
|
|
* about the return value of these functions. We use the
|
|
* cmpxchg to only update if an interrupt did not already
|
|
* do it for us. If the cmpxchg fails, we don't care.
|
|
*/
|
|
(void)local_cmpxchg(&next_page->write, old_write, val);
|
|
(void)local_cmpxchg(&next_page->entries, old_entries, eval);
|
|
|
|
/*
|
|
* No need to worry about races with clearing out the commit.
|
|
* it only can increment when a commit takes place. But that
|
|
* only happens in the outer most nested commit.
|
|
*/
|
|
local_set(&next_page->page->commit, 0);
|
|
|
|
/* Either we update tail_page or an interrupt does */
|
|
if (try_cmpxchg(&cpu_buffer->tail_page, &tail_page, next_page))
|
|
local_inc(&cpu_buffer->pages_touched);
|
|
}
|
|
}
|
|
|
|
static void rb_check_bpage(struct ring_buffer_per_cpu *cpu_buffer,
|
|
struct buffer_page *bpage)
|
|
{
|
|
unsigned long val = (unsigned long)bpage;
|
|
|
|
RB_WARN_ON(cpu_buffer, val & RB_FLAG_MASK);
|
|
}
|
|
|
|
/**
|
|
* rb_check_pages - integrity check of buffer pages
|
|
* @cpu_buffer: CPU buffer with pages to test
|
|
*
|
|
* As a safety measure we check to make sure the data pages have not
|
|
* been corrupted.
|
|
*/
|
|
static void rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
struct list_head *head = rb_list_head(cpu_buffer->pages);
|
|
struct list_head *tmp;
|
|
|
|
if (RB_WARN_ON(cpu_buffer,
|
|
rb_list_head(rb_list_head(head->next)->prev) != head))
|
|
return;
|
|
|
|
if (RB_WARN_ON(cpu_buffer,
|
|
rb_list_head(rb_list_head(head->prev)->next) != head))
|
|
return;
|
|
|
|
for (tmp = rb_list_head(head->next); tmp != head; tmp = rb_list_head(tmp->next)) {
|
|
if (RB_WARN_ON(cpu_buffer,
|
|
rb_list_head(rb_list_head(tmp->next)->prev) != tmp))
|
|
return;
|
|
|
|
if (RB_WARN_ON(cpu_buffer,
|
|
rb_list_head(rb_list_head(tmp->prev)->next) != tmp))
|
|
return;
|
|
}
|
|
}
|
|
|
|
static int __rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
|
|
long nr_pages, struct list_head *pages)
|
|
{
|
|
struct buffer_page *bpage, *tmp;
|
|
bool user_thread = current->mm != NULL;
|
|
gfp_t mflags;
|
|
long i;
|
|
|
|
/*
|
|
* Check if the available memory is there first.
|
|
* Note, si_mem_available() only gives us a rough estimate of available
|
|
* memory. It may not be accurate. But we don't care, we just want
|
|
* to prevent doing any allocation when it is obvious that it is
|
|
* not going to succeed.
|
|
*/
|
|
i = si_mem_available();
|
|
if (i < nr_pages)
|
|
return -ENOMEM;
|
|
|
|
/*
|
|
* __GFP_RETRY_MAYFAIL flag makes sure that the allocation fails
|
|
* gracefully without invoking oom-killer and the system is not
|
|
* destabilized.
|
|
*/
|
|
mflags = GFP_KERNEL | __GFP_RETRY_MAYFAIL;
|
|
|
|
/*
|
|
* If a user thread allocates too much, and si_mem_available()
|
|
* reports there's enough memory, even though there is not.
|
|
* Make sure the OOM killer kills this thread. This can happen
|
|
* even with RETRY_MAYFAIL because another task may be doing
|
|
* an allocation after this task has taken all memory.
|
|
* This is the task the OOM killer needs to take out during this
|
|
* loop, even if it was triggered by an allocation somewhere else.
|
|
*/
|
|
if (user_thread)
|
|
set_current_oom_origin();
|
|
for (i = 0; i < nr_pages; i++) {
|
|
struct page *page;
|
|
|
|
bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
|
|
mflags, cpu_to_node(cpu_buffer->cpu));
|
|
if (!bpage)
|
|
goto free_pages;
|
|
|
|
rb_check_bpage(cpu_buffer, bpage);
|
|
|
|
list_add(&bpage->list, pages);
|
|
|
|
page = alloc_pages_node(cpu_to_node(cpu_buffer->cpu),
|
|
mflags | __GFP_COMP | __GFP_ZERO,
|
|
cpu_buffer->buffer->subbuf_order);
|
|
if (!page)
|
|
goto free_pages;
|
|
bpage->page = page_address(page);
|
|
bpage->order = cpu_buffer->buffer->subbuf_order;
|
|
rb_init_page(bpage->page);
|
|
|
|
if (user_thread && fatal_signal_pending(current))
|
|
goto free_pages;
|
|
}
|
|
if (user_thread)
|
|
clear_current_oom_origin();
|
|
|
|
return 0;
|
|
|
|
free_pages:
|
|
list_for_each_entry_safe(bpage, tmp, pages, list) {
|
|
list_del_init(&bpage->list);
|
|
free_buffer_page(bpage);
|
|
}
|
|
if (user_thread)
|
|
clear_current_oom_origin();
|
|
|
|
return -ENOMEM;
|
|
}
|
|
|
|
static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
|
|
unsigned long nr_pages)
|
|
{
|
|
LIST_HEAD(pages);
|
|
|
|
WARN_ON(!nr_pages);
|
|
|
|
if (__rb_allocate_pages(cpu_buffer, nr_pages, &pages))
|
|
return -ENOMEM;
|
|
|
|
/*
|
|
* The ring buffer page list is a circular list that does not
|
|
* start and end with a list head. All page list items point to
|
|
* other pages.
|
|
*/
|
|
cpu_buffer->pages = pages.next;
|
|
list_del(&pages);
|
|
|
|
cpu_buffer->nr_pages = nr_pages;
|
|
|
|
rb_check_pages(cpu_buffer);
|
|
|
|
return 0;
|
|
}
|
|
|
|
static struct ring_buffer_per_cpu *
|
|
rb_allocate_cpu_buffer(struct trace_buffer *buffer, long nr_pages, int cpu)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
struct buffer_page *bpage;
|
|
struct page *page;
|
|
int ret;
|
|
|
|
cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()),
|
|
GFP_KERNEL, cpu_to_node(cpu));
|
|
if (!cpu_buffer)
|
|
return NULL;
|
|
|
|
cpu_buffer->cpu = cpu;
|
|
cpu_buffer->buffer = buffer;
|
|
raw_spin_lock_init(&cpu_buffer->reader_lock);
|
|
lockdep_set_class(&cpu_buffer->reader_lock, buffer->reader_lock_key);
|
|
cpu_buffer->lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
|
|
INIT_WORK(&cpu_buffer->update_pages_work, update_pages_handler);
|
|
init_completion(&cpu_buffer->update_done);
|
|
init_irq_work(&cpu_buffer->irq_work.work, rb_wake_up_waiters);
|
|
init_waitqueue_head(&cpu_buffer->irq_work.waiters);
|
|
init_waitqueue_head(&cpu_buffer->irq_work.full_waiters);
|
|
mutex_init(&cpu_buffer->mapping_lock);
|
|
|
|
bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
|
|
GFP_KERNEL, cpu_to_node(cpu));
|
|
if (!bpage)
|
|
goto fail_free_buffer;
|
|
|
|
rb_check_bpage(cpu_buffer, bpage);
|
|
|
|
cpu_buffer->reader_page = bpage;
|
|
|
|
page = alloc_pages_node(cpu_to_node(cpu), GFP_KERNEL | __GFP_COMP | __GFP_ZERO,
|
|
cpu_buffer->buffer->subbuf_order);
|
|
if (!page)
|
|
goto fail_free_reader;
|
|
bpage->page = page_address(page);
|
|
rb_init_page(bpage->page);
|
|
|
|
INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
|
|
INIT_LIST_HEAD(&cpu_buffer->new_pages);
|
|
|
|
ret = rb_allocate_pages(cpu_buffer, nr_pages);
|
|
if (ret < 0)
|
|
goto fail_free_reader;
|
|
|
|
cpu_buffer->head_page
|
|
= list_entry(cpu_buffer->pages, struct buffer_page, list);
|
|
cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;
|
|
|
|
rb_head_page_activate(cpu_buffer);
|
|
|
|
return cpu_buffer;
|
|
|
|
fail_free_reader:
|
|
free_buffer_page(cpu_buffer->reader_page);
|
|
|
|
fail_free_buffer:
|
|
kfree(cpu_buffer);
|
|
return NULL;
|
|
}
|
|
|
|
static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
struct list_head *head = cpu_buffer->pages;
|
|
struct buffer_page *bpage, *tmp;
|
|
|
|
irq_work_sync(&cpu_buffer->irq_work.work);
|
|
|
|
free_buffer_page(cpu_buffer->reader_page);
|
|
|
|
if (head) {
|
|
rb_head_page_deactivate(cpu_buffer);
|
|
|
|
list_for_each_entry_safe(bpage, tmp, head, list) {
|
|
list_del_init(&bpage->list);
|
|
free_buffer_page(bpage);
|
|
}
|
|
bpage = list_entry(head, struct buffer_page, list);
|
|
free_buffer_page(bpage);
|
|
}
|
|
|
|
free_page((unsigned long)cpu_buffer->free_page);
|
|
|
|
kfree(cpu_buffer);
|
|
}
|
|
|
|
/**
|
|
* __ring_buffer_alloc - allocate a new ring_buffer
|
|
* @size: the size in bytes per cpu that is needed.
|
|
* @flags: attributes to set for the ring buffer.
|
|
* @key: ring buffer reader_lock_key.
|
|
*
|
|
* Currently the only flag that is available is the RB_FL_OVERWRITE
|
|
* flag. This flag means that the buffer will overwrite old data
|
|
* when the buffer wraps. If this flag is not set, the buffer will
|
|
* drop data when the tail hits the head.
|
|
*/
|
|
struct trace_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
|
|
struct lock_class_key *key)
|
|
{
|
|
struct trace_buffer *buffer;
|
|
long nr_pages;
|
|
int bsize;
|
|
int cpu;
|
|
int ret;
|
|
|
|
/* keep it in its own cache line */
|
|
buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
|
|
GFP_KERNEL);
|
|
if (!buffer)
|
|
return NULL;
|
|
|
|
if (!zalloc_cpumask_var(&buffer->cpumask, GFP_KERNEL))
|
|
goto fail_free_buffer;
|
|
|
|
/* Default buffer page size - one system page */
|
|
buffer->subbuf_order = 0;
|
|
buffer->subbuf_size = PAGE_SIZE - BUF_PAGE_HDR_SIZE;
|
|
|
|
/* Max payload is buffer page size - header (8bytes) */
|
|
buffer->max_data_size = buffer->subbuf_size - (sizeof(u32) * 2);
|
|
|
|
nr_pages = DIV_ROUND_UP(size, buffer->subbuf_size);
|
|
buffer->flags = flags;
|
|
buffer->clock = trace_clock_local;
|
|
buffer->reader_lock_key = key;
|
|
|
|
init_irq_work(&buffer->irq_work.work, rb_wake_up_waiters);
|
|
init_waitqueue_head(&buffer->irq_work.waiters);
|
|
|
|
/* need at least two pages */
|
|
if (nr_pages < 2)
|
|
nr_pages = 2;
|
|
|
|
buffer->cpus = nr_cpu_ids;
|
|
|
|
bsize = sizeof(void *) * nr_cpu_ids;
|
|
buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()),
|
|
GFP_KERNEL);
|
|
if (!buffer->buffers)
|
|
goto fail_free_cpumask;
|
|
|
|
cpu = raw_smp_processor_id();
|
|
cpumask_set_cpu(cpu, buffer->cpumask);
|
|
buffer->buffers[cpu] = rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
|
|
if (!buffer->buffers[cpu])
|
|
goto fail_free_buffers;
|
|
|
|
ret = cpuhp_state_add_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
|
|
if (ret < 0)
|
|
goto fail_free_buffers;
|
|
|
|
mutex_init(&buffer->mutex);
|
|
|
|
return buffer;
|
|
|
|
fail_free_buffers:
|
|
for_each_buffer_cpu(buffer, cpu) {
|
|
if (buffer->buffers[cpu])
|
|
rb_free_cpu_buffer(buffer->buffers[cpu]);
|
|
}
|
|
kfree(buffer->buffers);
|
|
|
|
fail_free_cpumask:
|
|
free_cpumask_var(buffer->cpumask);
|
|
|
|
fail_free_buffer:
|
|
kfree(buffer);
|
|
return NULL;
|
|
}
|
|
EXPORT_SYMBOL_GPL(__ring_buffer_alloc);
|
|
|
|
/**
|
|
* ring_buffer_free - free a ring buffer.
|
|
* @buffer: the buffer to free.
|
|
*/
|
|
void
|
|
ring_buffer_free(struct trace_buffer *buffer)
|
|
{
|
|
int cpu;
|
|
|
|
cpuhp_state_remove_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node);
|
|
|
|
irq_work_sync(&buffer->irq_work.work);
|
|
|
|
for_each_buffer_cpu(buffer, cpu)
|
|
rb_free_cpu_buffer(buffer->buffers[cpu]);
|
|
|
|
kfree(buffer->buffers);
|
|
free_cpumask_var(buffer->cpumask);
|
|
|
|
kfree(buffer);
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_free);
|
|
|
|
void ring_buffer_set_clock(struct trace_buffer *buffer,
|
|
u64 (*clock)(void))
|
|
{
|
|
buffer->clock = clock;
|
|
}
|
|
|
|
void ring_buffer_set_time_stamp_abs(struct trace_buffer *buffer, bool abs)
|
|
{
|
|
buffer->time_stamp_abs = abs;
|
|
}
|
|
|
|
bool ring_buffer_time_stamp_abs(struct trace_buffer *buffer)
|
|
{
|
|
return buffer->time_stamp_abs;
|
|
}
|
|
|
|
static inline unsigned long rb_page_entries(struct buffer_page *bpage)
|
|
{
|
|
return local_read(&bpage->entries) & RB_WRITE_MASK;
|
|
}
|
|
|
|
static inline unsigned long rb_page_write(struct buffer_page *bpage)
|
|
{
|
|
return local_read(&bpage->write) & RB_WRITE_MASK;
|
|
}
|
|
|
|
static bool
|
|
rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned long nr_pages)
|
|
{
|
|
struct list_head *tail_page, *to_remove, *next_page;
|
|
struct buffer_page *to_remove_page, *tmp_iter_page;
|
|
struct buffer_page *last_page, *first_page;
|
|
unsigned long nr_removed;
|
|
unsigned long head_bit;
|
|
int page_entries;
|
|
|
|
head_bit = 0;
|
|
|
|
raw_spin_lock_irq(&cpu_buffer->reader_lock);
|
|
atomic_inc(&cpu_buffer->record_disabled);
|
|
/*
|
|
* We don't race with the readers since we have acquired the reader
|
|
* lock. We also don't race with writers after disabling recording.
|
|
* This makes it easy to figure out the first and the last page to be
|
|
* removed from the list. We unlink all the pages in between including
|
|
* the first and last pages. This is done in a busy loop so that we
|
|
* lose the least number of traces.
|
|
* The pages are freed after we restart recording and unlock readers.
|
|
*/
|
|
tail_page = &cpu_buffer->tail_page->list;
|
|
|
|
/*
|
|
* tail page might be on reader page, we remove the next page
|
|
* from the ring buffer
|
|
*/
|
|
if (cpu_buffer->tail_page == cpu_buffer->reader_page)
|
|
tail_page = rb_list_head(tail_page->next);
|
|
to_remove = tail_page;
|
|
|
|
/* start of pages to remove */
|
|
first_page = list_entry(rb_list_head(to_remove->next),
|
|
struct buffer_page, list);
|
|
|
|
for (nr_removed = 0; nr_removed < nr_pages; nr_removed++) {
|
|
to_remove = rb_list_head(to_remove)->next;
|
|
head_bit |= (unsigned long)to_remove & RB_PAGE_HEAD;
|
|
}
|
|
/* Read iterators need to reset themselves when some pages removed */
|
|
cpu_buffer->pages_removed += nr_removed;
|
|
|
|
next_page = rb_list_head(to_remove)->next;
|
|
|
|
/*
|
|
* Now we remove all pages between tail_page and next_page.
|
|
* Make sure that we have head_bit value preserved for the
|
|
* next page
|
|
*/
|
|
tail_page->next = (struct list_head *)((unsigned long)next_page |
|
|
head_bit);
|
|
next_page = rb_list_head(next_page);
|
|
next_page->prev = tail_page;
|
|
|
|
/* make sure pages points to a valid page in the ring buffer */
|
|
cpu_buffer->pages = next_page;
|
|
|
|
/* update head page */
|
|
if (head_bit)
|
|
cpu_buffer->head_page = list_entry(next_page,
|
|
struct buffer_page, list);
|
|
|
|
/* pages are removed, resume tracing and then free the pages */
|
|
atomic_dec(&cpu_buffer->record_disabled);
|
|
raw_spin_unlock_irq(&cpu_buffer->reader_lock);
|
|
|
|
RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages));
|
|
|
|
/* last buffer page to remove */
|
|
last_page = list_entry(rb_list_head(to_remove), struct buffer_page,
|
|
list);
|
|
tmp_iter_page = first_page;
|
|
|
|
do {
|
|
cond_resched();
|
|
|
|
to_remove_page = tmp_iter_page;
|
|
rb_inc_page(&tmp_iter_page);
|
|
|
|
/* update the counters */
|
|
page_entries = rb_page_entries(to_remove_page);
|
|
if (page_entries) {
|
|
/*
|
|
* If something was added to this page, it was full
|
|
* since it is not the tail page. So we deduct the
|
|
* bytes consumed in ring buffer from here.
|
|
* Increment overrun to account for the lost events.
|
|
*/
|
|
local_add(page_entries, &cpu_buffer->overrun);
|
|
local_sub(rb_page_commit(to_remove_page), &cpu_buffer->entries_bytes);
|
|
local_inc(&cpu_buffer->pages_lost);
|
|
}
|
|
|
|
/*
|
|
* We have already removed references to this list item, just
|
|
* free up the buffer_page and its page
|
|
*/
|
|
free_buffer_page(to_remove_page);
|
|
nr_removed--;
|
|
|
|
} while (to_remove_page != last_page);
|
|
|
|
RB_WARN_ON(cpu_buffer, nr_removed);
|
|
|
|
return nr_removed == 0;
|
|
}
|
|
|
|
static bool
|
|
rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
struct list_head *pages = &cpu_buffer->new_pages;
|
|
unsigned long flags;
|
|
bool success;
|
|
int retries;
|
|
|
|
/* Can be called at early boot up, where interrupts must not been enabled */
|
|
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
|
|
/*
|
|
* We are holding the reader lock, so the reader page won't be swapped
|
|
* in the ring buffer. Now we are racing with the writer trying to
|
|
* move head page and the tail page.
|
|
* We are going to adapt the reader page update process where:
|
|
* 1. We first splice the start and end of list of new pages between
|
|
* the head page and its previous page.
|
|
* 2. We cmpxchg the prev_page->next to point from head page to the
|
|
* start of new pages list.
|
|
* 3. Finally, we update the head->prev to the end of new list.
|
|
*
|
|
* We will try this process 10 times, to make sure that we don't keep
|
|
* spinning.
|
|
*/
|
|
retries = 10;
|
|
success = false;
|
|
while (retries--) {
|
|
struct list_head *head_page, *prev_page;
|
|
struct list_head *last_page, *first_page;
|
|
struct list_head *head_page_with_bit;
|
|
struct buffer_page *hpage = rb_set_head_page(cpu_buffer);
|
|
|
|
if (!hpage)
|
|
break;
|
|
head_page = &hpage->list;
|
|
prev_page = head_page->prev;
|
|
|
|
first_page = pages->next;
|
|
last_page = pages->prev;
|
|
|
|
head_page_with_bit = (struct list_head *)
|
|
((unsigned long)head_page | RB_PAGE_HEAD);
|
|
|
|
last_page->next = head_page_with_bit;
|
|
first_page->prev = prev_page;
|
|
|
|
/* caution: head_page_with_bit gets updated on cmpxchg failure */
|
|
if (try_cmpxchg(&prev_page->next,
|
|
&head_page_with_bit, first_page)) {
|
|
/*
|
|
* yay, we replaced the page pointer to our new list,
|
|
* now, we just have to update to head page's prev
|
|
* pointer to point to end of list
|
|
*/
|
|
head_page->prev = last_page;
|
|
success = true;
|
|
break;
|
|
}
|
|
}
|
|
|
|
if (success)
|
|
INIT_LIST_HEAD(pages);
|
|
/*
|
|
* If we weren't successful in adding in new pages, warn and stop
|
|
* tracing
|
|
*/
|
|
RB_WARN_ON(cpu_buffer, !success);
|
|
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
|
|
|
|
/* free pages if they weren't inserted */
|
|
if (!success) {
|
|
struct buffer_page *bpage, *tmp;
|
|
list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
|
|
list) {
|
|
list_del_init(&bpage->list);
|
|
free_buffer_page(bpage);
|
|
}
|
|
}
|
|
return success;
|
|
}
|
|
|
|
static void rb_update_pages(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
bool success;
|
|
|
|
if (cpu_buffer->nr_pages_to_update > 0)
|
|
success = rb_insert_pages(cpu_buffer);
|
|
else
|
|
success = rb_remove_pages(cpu_buffer,
|
|
-cpu_buffer->nr_pages_to_update);
|
|
|
|
if (success)
|
|
cpu_buffer->nr_pages += cpu_buffer->nr_pages_to_update;
|
|
}
|
|
|
|
static void update_pages_handler(struct work_struct *work)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer = container_of(work,
|
|
struct ring_buffer_per_cpu, update_pages_work);
|
|
rb_update_pages(cpu_buffer);
|
|
complete(&cpu_buffer->update_done);
|
|
}
|
|
|
|
/**
|
|
* ring_buffer_resize - resize the ring buffer
|
|
* @buffer: the buffer to resize.
|
|
* @size: the new size.
|
|
* @cpu_id: the cpu buffer to resize
|
|
*
|
|
* Minimum size is 2 * buffer->subbuf_size.
|
|
*
|
|
* Returns 0 on success and < 0 on failure.
|
|
*/
|
|
int ring_buffer_resize(struct trace_buffer *buffer, unsigned long size,
|
|
int cpu_id)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
unsigned long nr_pages;
|
|
int cpu, err;
|
|
|
|
/*
|
|
* Always succeed at resizing a non-existent buffer:
|
|
*/
|
|
if (!buffer)
|
|
return 0;
|
|
|
|
/* Make sure the requested buffer exists */
|
|
if (cpu_id != RING_BUFFER_ALL_CPUS &&
|
|
!cpumask_test_cpu(cpu_id, buffer->cpumask))
|
|
return 0;
|
|
|
|
nr_pages = DIV_ROUND_UP(size, buffer->subbuf_size);
|
|
|
|
/* we need a minimum of two pages */
|
|
if (nr_pages < 2)
|
|
nr_pages = 2;
|
|
|
|
/* prevent another thread from changing buffer sizes */
|
|
mutex_lock(&buffer->mutex);
|
|
atomic_inc(&buffer->resizing);
|
|
|
|
if (cpu_id == RING_BUFFER_ALL_CPUS) {
|
|
/*
|
|
* Don't succeed if resizing is disabled, as a reader might be
|
|
* manipulating the ring buffer and is expecting a sane state while
|
|
* this is true.
|
|
*/
|
|
for_each_buffer_cpu(buffer, cpu) {
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
if (atomic_read(&cpu_buffer->resize_disabled)) {
|
|
err = -EBUSY;
|
|
goto out_err_unlock;
|
|
}
|
|
}
|
|
|
|
/* calculate the pages to update */
|
|
for_each_buffer_cpu(buffer, cpu) {
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
|
|
cpu_buffer->nr_pages_to_update = nr_pages -
|
|
cpu_buffer->nr_pages;
|
|
/*
|
|
* nothing more to do for removing pages or no update
|
|
*/
|
|
if (cpu_buffer->nr_pages_to_update <= 0)
|
|
continue;
|
|
/*
|
|
* to add pages, make sure all new pages can be
|
|
* allocated without receiving ENOMEM
|
|
*/
|
|
INIT_LIST_HEAD(&cpu_buffer->new_pages);
|
|
if (__rb_allocate_pages(cpu_buffer, cpu_buffer->nr_pages_to_update,
|
|
&cpu_buffer->new_pages)) {
|
|
/* not enough memory for new pages */
|
|
err = -ENOMEM;
|
|
goto out_err;
|
|
}
|
|
|
|
cond_resched();
|
|
}
|
|
|
|
cpus_read_lock();
|
|
/*
|
|
* Fire off all the required work handlers
|
|
* We can't schedule on offline CPUs, but it's not necessary
|
|
* since we can change their buffer sizes without any race.
|
|
*/
|
|
for_each_buffer_cpu(buffer, cpu) {
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
if (!cpu_buffer->nr_pages_to_update)
|
|
continue;
|
|
|
|
/* Can't run something on an offline CPU. */
|
|
if (!cpu_online(cpu)) {
|
|
rb_update_pages(cpu_buffer);
|
|
cpu_buffer->nr_pages_to_update = 0;
|
|
} else {
|
|
/* Run directly if possible. */
|
|
migrate_disable();
|
|
if (cpu != smp_processor_id()) {
|
|
migrate_enable();
|
|
schedule_work_on(cpu,
|
|
&cpu_buffer->update_pages_work);
|
|
} else {
|
|
update_pages_handler(&cpu_buffer->update_pages_work);
|
|
migrate_enable();
|
|
}
|
|
}
|
|
}
|
|
|
|
/* wait for all the updates to complete */
|
|
for_each_buffer_cpu(buffer, cpu) {
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
if (!cpu_buffer->nr_pages_to_update)
|
|
continue;
|
|
|
|
if (cpu_online(cpu))
|
|
wait_for_completion(&cpu_buffer->update_done);
|
|
cpu_buffer->nr_pages_to_update = 0;
|
|
}
|
|
|
|
cpus_read_unlock();
|
|
} else {
|
|
cpu_buffer = buffer->buffers[cpu_id];
|
|
|
|
if (nr_pages == cpu_buffer->nr_pages)
|
|
goto out;
|
|
|
|
/*
|
|
* Don't succeed if resizing is disabled, as a reader might be
|
|
* manipulating the ring buffer and is expecting a sane state while
|
|
* this is true.
|
|
*/
|
|
if (atomic_read(&cpu_buffer->resize_disabled)) {
|
|
err = -EBUSY;
|
|
goto out_err_unlock;
|
|
}
|
|
|
|
cpu_buffer->nr_pages_to_update = nr_pages -
|
|
cpu_buffer->nr_pages;
|
|
|
|
INIT_LIST_HEAD(&cpu_buffer->new_pages);
|
|
if (cpu_buffer->nr_pages_to_update > 0 &&
|
|
__rb_allocate_pages(cpu_buffer, cpu_buffer->nr_pages_to_update,
|
|
&cpu_buffer->new_pages)) {
|
|
err = -ENOMEM;
|
|
goto out_err;
|
|
}
|
|
|
|
cpus_read_lock();
|
|
|
|
/* Can't run something on an offline CPU. */
|
|
if (!cpu_online(cpu_id))
|
|
rb_update_pages(cpu_buffer);
|
|
else {
|
|
/* Run directly if possible. */
|
|
migrate_disable();
|
|
if (cpu_id == smp_processor_id()) {
|
|
rb_update_pages(cpu_buffer);
|
|
migrate_enable();
|
|
} else {
|
|
migrate_enable();
|
|
schedule_work_on(cpu_id,
|
|
&cpu_buffer->update_pages_work);
|
|
wait_for_completion(&cpu_buffer->update_done);
|
|
}
|
|
}
|
|
|
|
cpu_buffer->nr_pages_to_update = 0;
|
|
cpus_read_unlock();
|
|
}
|
|
|
|
out:
|
|
/*
|
|
* The ring buffer resize can happen with the ring buffer
|
|
* enabled, so that the update disturbs the tracing as little
|
|
* as possible. But if the buffer is disabled, we do not need
|
|
* to worry about that, and we can take the time to verify
|
|
* that the buffer is not corrupt.
|
|
*/
|
|
if (atomic_read(&buffer->record_disabled)) {
|
|
atomic_inc(&buffer->record_disabled);
|
|
/*
|
|
* Even though the buffer was disabled, we must make sure
|
|
* that it is truly disabled before calling rb_check_pages.
|
|
* There could have been a race between checking
|
|
* record_disable and incrementing it.
|
|
*/
|
|
synchronize_rcu();
|
|
for_each_buffer_cpu(buffer, cpu) {
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
rb_check_pages(cpu_buffer);
|
|
}
|
|
atomic_dec(&buffer->record_disabled);
|
|
}
|
|
|
|
atomic_dec(&buffer->resizing);
|
|
mutex_unlock(&buffer->mutex);
|
|
return 0;
|
|
|
|
out_err:
|
|
for_each_buffer_cpu(buffer, cpu) {
|
|
struct buffer_page *bpage, *tmp;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
cpu_buffer->nr_pages_to_update = 0;
|
|
|
|
if (list_empty(&cpu_buffer->new_pages))
|
|
continue;
|
|
|
|
list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages,
|
|
list) {
|
|
list_del_init(&bpage->list);
|
|
free_buffer_page(bpage);
|
|
}
|
|
}
|
|
out_err_unlock:
|
|
atomic_dec(&buffer->resizing);
|
|
mutex_unlock(&buffer->mutex);
|
|
return err;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_resize);
|
|
|
|
void ring_buffer_change_overwrite(struct trace_buffer *buffer, int val)
|
|
{
|
|
mutex_lock(&buffer->mutex);
|
|
if (val)
|
|
buffer->flags |= RB_FL_OVERWRITE;
|
|
else
|
|
buffer->flags &= ~RB_FL_OVERWRITE;
|
|
mutex_unlock(&buffer->mutex);
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite);
|
|
|
|
static __always_inline void *__rb_page_index(struct buffer_page *bpage, unsigned index)
|
|
{
|
|
return bpage->page->data + index;
|
|
}
|
|
|
|
static __always_inline struct ring_buffer_event *
|
|
rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
return __rb_page_index(cpu_buffer->reader_page,
|
|
cpu_buffer->reader_page->read);
|
|
}
|
|
|
|
static struct ring_buffer_event *
|
|
rb_iter_head_event(struct ring_buffer_iter *iter)
|
|
{
|
|
struct ring_buffer_event *event;
|
|
struct buffer_page *iter_head_page = iter->head_page;
|
|
unsigned long commit;
|
|
unsigned length;
|
|
|
|
if (iter->head != iter->next_event)
|
|
return iter->event;
|
|
|
|
/*
|
|
* When the writer goes across pages, it issues a cmpxchg which
|
|
* is a mb(), which will synchronize with the rmb here.
|
|
* (see rb_tail_page_update() and __rb_reserve_next())
|
|
*/
|
|
commit = rb_page_commit(iter_head_page);
|
|
smp_rmb();
|
|
|
|
/* An event needs to be at least 8 bytes in size */
|
|
if (iter->head > commit - 8)
|
|
goto reset;
|
|
|
|
event = __rb_page_index(iter_head_page, iter->head);
|
|
length = rb_event_length(event);
|
|
|
|
/*
|
|
* READ_ONCE() doesn't work on functions and we don't want the
|
|
* compiler doing any crazy optimizations with length.
|
|
*/
|
|
barrier();
|
|
|
|
if ((iter->head + length) > commit || length > iter->event_size)
|
|
/* Writer corrupted the read? */
|
|
goto reset;
|
|
|
|
memcpy(iter->event, event, length);
|
|
/*
|
|
* If the page stamp is still the same after this rmb() then the
|
|
* event was safely copied without the writer entering the page.
|
|
*/
|
|
smp_rmb();
|
|
|
|
/* Make sure the page didn't change since we read this */
|
|
if (iter->page_stamp != iter_head_page->page->time_stamp ||
|
|
commit > rb_page_commit(iter_head_page))
|
|
goto reset;
|
|
|
|
iter->next_event = iter->head + length;
|
|
return iter->event;
|
|
reset:
|
|
/* Reset to the beginning */
|
|
iter->page_stamp = iter->read_stamp = iter->head_page->page->time_stamp;
|
|
iter->head = 0;
|
|
iter->next_event = 0;
|
|
iter->missed_events = 1;
|
|
return NULL;
|
|
}
|
|
|
|
/* Size is determined by what has been committed */
|
|
static __always_inline unsigned rb_page_size(struct buffer_page *bpage)
|
|
{
|
|
return rb_page_commit(bpage) & ~RB_MISSED_MASK;
|
|
}
|
|
|
|
static __always_inline unsigned
|
|
rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
return rb_page_commit(cpu_buffer->commit_page);
|
|
}
|
|
|
|
static __always_inline unsigned
|
|
rb_event_index(struct ring_buffer_per_cpu *cpu_buffer, struct ring_buffer_event *event)
|
|
{
|
|
unsigned long addr = (unsigned long)event;
|
|
|
|
addr &= (PAGE_SIZE << cpu_buffer->buffer->subbuf_order) - 1;
|
|
|
|
return addr - BUF_PAGE_HDR_SIZE;
|
|
}
|
|
|
|
static void rb_inc_iter(struct ring_buffer_iter *iter)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
|
|
|
|
/*
|
|
* The iterator could be on the reader page (it starts there).
|
|
* But the head could have moved, since the reader was
|
|
* found. Check for this case and assign the iterator
|
|
* to the head page instead of next.
|
|
*/
|
|
if (iter->head_page == cpu_buffer->reader_page)
|
|
iter->head_page = rb_set_head_page(cpu_buffer);
|
|
else
|
|
rb_inc_page(&iter->head_page);
|
|
|
|
iter->page_stamp = iter->read_stamp = iter->head_page->page->time_stamp;
|
|
iter->head = 0;
|
|
iter->next_event = 0;
|
|
}
|
|
|
|
/*
|
|
* rb_handle_head_page - writer hit the head page
|
|
*
|
|
* Returns: +1 to retry page
|
|
* 0 to continue
|
|
* -1 on error
|
|
*/
|
|
static int
|
|
rb_handle_head_page(struct ring_buffer_per_cpu *cpu_buffer,
|
|
struct buffer_page *tail_page,
|
|
struct buffer_page *next_page)
|
|
{
|
|
struct buffer_page *new_head;
|
|
int entries;
|
|
int type;
|
|
int ret;
|
|
|
|
entries = rb_page_entries(next_page);
|
|
|
|
/*
|
|
* The hard part is here. We need to move the head
|
|
* forward, and protect against both readers on
|
|
* other CPUs and writers coming in via interrupts.
|
|
*/
|
|
type = rb_head_page_set_update(cpu_buffer, next_page, tail_page,
|
|
RB_PAGE_HEAD);
|
|
|
|
/*
|
|
* type can be one of four:
|
|
* NORMAL - an interrupt already moved it for us
|
|
* HEAD - we are the first to get here.
|
|
* UPDATE - we are the interrupt interrupting
|
|
* a current move.
|
|
* MOVED - a reader on another CPU moved the next
|
|
* pointer to its reader page. Give up
|
|
* and try again.
|
|
*/
|
|
|
|
switch (type) {
|
|
case RB_PAGE_HEAD:
|
|
/*
|
|
* We changed the head to UPDATE, thus
|
|
* it is our responsibility to update
|
|
* the counters.
|
|
*/
|
|
local_add(entries, &cpu_buffer->overrun);
|
|
local_sub(rb_page_commit(next_page), &cpu_buffer->entries_bytes);
|
|
local_inc(&cpu_buffer->pages_lost);
|
|
|
|
/*
|
|
* The entries will be zeroed out when we move the
|
|
* tail page.
|
|
*/
|
|
|
|
/* still more to do */
|
|
break;
|
|
|
|
case RB_PAGE_UPDATE:
|
|
/*
|
|
* This is an interrupt that interrupt the
|
|
* previous update. Still more to do.
|
|
*/
|
|
break;
|
|
case RB_PAGE_NORMAL:
|
|
/*
|
|
* An interrupt came in before the update
|
|
* and processed this for us.
|
|
* Nothing left to do.
|
|
*/
|
|
return 1;
|
|
case RB_PAGE_MOVED:
|
|
/*
|
|
* The reader is on another CPU and just did
|
|
* a swap with our next_page.
|
|
* Try again.
|
|
*/
|
|
return 1;
|
|
default:
|
|
RB_WARN_ON(cpu_buffer, 1); /* WTF??? */
|
|
return -1;
|
|
}
|
|
|
|
/*
|
|
* Now that we are here, the old head pointer is
|
|
* set to UPDATE. This will keep the reader from
|
|
* swapping the head page with the reader page.
|
|
* The reader (on another CPU) will spin till
|
|
* we are finished.
|
|
*
|
|
* We just need to protect against interrupts
|
|
* doing the job. We will set the next pointer
|
|
* to HEAD. After that, we set the old pointer
|
|
* to NORMAL, but only if it was HEAD before.
|
|
* otherwise we are an interrupt, and only
|
|
* want the outer most commit to reset it.
|
|
*/
|
|
new_head = next_page;
|
|
rb_inc_page(&new_head);
|
|
|
|
ret = rb_head_page_set_head(cpu_buffer, new_head, next_page,
|
|
RB_PAGE_NORMAL);
|
|
|
|
/*
|
|
* Valid returns are:
|
|
* HEAD - an interrupt came in and already set it.
|
|
* NORMAL - One of two things:
|
|
* 1) We really set it.
|
|
* 2) A bunch of interrupts came in and moved
|
|
* the page forward again.
|
|
*/
|
|
switch (ret) {
|
|
case RB_PAGE_HEAD:
|
|
case RB_PAGE_NORMAL:
|
|
/* OK */
|
|
break;
|
|
default:
|
|
RB_WARN_ON(cpu_buffer, 1);
|
|
return -1;
|
|
}
|
|
|
|
/*
|
|
* It is possible that an interrupt came in,
|
|
* set the head up, then more interrupts came in
|
|
* and moved it again. When we get back here,
|
|
* the page would have been set to NORMAL but we
|
|
* just set it back to HEAD.
|
|
*
|
|
* How do you detect this? Well, if that happened
|
|
* the tail page would have moved.
|
|
*/
|
|
if (ret == RB_PAGE_NORMAL) {
|
|
struct buffer_page *buffer_tail_page;
|
|
|
|
buffer_tail_page = READ_ONCE(cpu_buffer->tail_page);
|
|
/*
|
|
* If the tail had moved passed next, then we need
|
|
* to reset the pointer.
|
|
*/
|
|
if (buffer_tail_page != tail_page &&
|
|
buffer_tail_page != next_page)
|
|
rb_head_page_set_normal(cpu_buffer, new_head,
|
|
next_page,
|
|
RB_PAGE_HEAD);
|
|
}
|
|
|
|
/*
|
|
* If this was the outer most commit (the one that
|
|
* changed the original pointer from HEAD to UPDATE),
|
|
* then it is up to us to reset it to NORMAL.
|
|
*/
|
|
if (type == RB_PAGE_HEAD) {
|
|
ret = rb_head_page_set_normal(cpu_buffer, next_page,
|
|
tail_page,
|
|
RB_PAGE_UPDATE);
|
|
if (RB_WARN_ON(cpu_buffer,
|
|
ret != RB_PAGE_UPDATE))
|
|
return -1;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
static inline void
|
|
rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer,
|
|
unsigned long tail, struct rb_event_info *info)
|
|
{
|
|
unsigned long bsize = READ_ONCE(cpu_buffer->buffer->subbuf_size);
|
|
struct buffer_page *tail_page = info->tail_page;
|
|
struct ring_buffer_event *event;
|
|
unsigned long length = info->length;
|
|
|
|
/*
|
|
* Only the event that crossed the page boundary
|
|
* must fill the old tail_page with padding.
|
|
*/
|
|
if (tail >= bsize) {
|
|
/*
|
|
* If the page was filled, then we still need
|
|
* to update the real_end. Reset it to zero
|
|
* and the reader will ignore it.
|
|
*/
|
|
if (tail == bsize)
|
|
tail_page->real_end = 0;
|
|
|
|
local_sub(length, &tail_page->write);
|
|
return;
|
|
}
|
|
|
|
event = __rb_page_index(tail_page, tail);
|
|
|
|
/*
|
|
* Save the original length to the meta data.
|
|
* This will be used by the reader to add lost event
|
|
* counter.
|
|
*/
|
|
tail_page->real_end = tail;
|
|
|
|
/*
|
|
* If this event is bigger than the minimum size, then
|
|
* we need to be careful that we don't subtract the
|
|
* write counter enough to allow another writer to slip
|
|
* in on this page.
|
|
* We put in a discarded commit instead, to make sure
|
|
* that this space is not used again, and this space will
|
|
* not be accounted into 'entries_bytes'.
|
|
*
|
|
* If we are less than the minimum size, we don't need to
|
|
* worry about it.
|
|
*/
|
|
if (tail > (bsize - RB_EVNT_MIN_SIZE)) {
|
|
/* No room for any events */
|
|
|
|
/* Mark the rest of the page with padding */
|
|
rb_event_set_padding(event);
|
|
|
|
/* Make sure the padding is visible before the write update */
|
|
smp_wmb();
|
|
|
|
/* Set the write back to the previous setting */
|
|
local_sub(length, &tail_page->write);
|
|
return;
|
|
}
|
|
|
|
/* Put in a discarded event */
|
|
event->array[0] = (bsize - tail) - RB_EVNT_HDR_SIZE;
|
|
event->type_len = RINGBUF_TYPE_PADDING;
|
|
/* time delta must be non zero */
|
|
event->time_delta = 1;
|
|
|
|
/* account for padding bytes */
|
|
local_add(bsize - tail, &cpu_buffer->entries_bytes);
|
|
|
|
/* Make sure the padding is visible before the tail_page->write update */
|
|
smp_wmb();
|
|
|
|
/* Set write to end of buffer */
|
|
length = (tail + length) - bsize;
|
|
local_sub(length, &tail_page->write);
|
|
}
|
|
|
|
static inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer);
|
|
|
|
/*
|
|
* This is the slow path, force gcc not to inline it.
|
|
*/
|
|
static noinline struct ring_buffer_event *
|
|
rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer,
|
|
unsigned long tail, struct rb_event_info *info)
|
|
{
|
|
struct buffer_page *tail_page = info->tail_page;
|
|
struct buffer_page *commit_page = cpu_buffer->commit_page;
|
|
struct trace_buffer *buffer = cpu_buffer->buffer;
|
|
struct buffer_page *next_page;
|
|
int ret;
|
|
|
|
next_page = tail_page;
|
|
|
|
rb_inc_page(&next_page);
|
|
|
|
/*
|
|
* If for some reason, we had an interrupt storm that made
|
|
* it all the way around the buffer, bail, and warn
|
|
* about it.
|
|
*/
|
|
if (unlikely(next_page == commit_page)) {
|
|
local_inc(&cpu_buffer->commit_overrun);
|
|
goto out_reset;
|
|
}
|
|
|
|
/*
|
|
* This is where the fun begins!
|
|
*
|
|
* We are fighting against races between a reader that
|
|
* could be on another CPU trying to swap its reader
|
|
* page with the buffer head.
|
|
*
|
|
* We are also fighting against interrupts coming in and
|
|
* moving the head or tail on us as well.
|
|
*
|
|
* If the next page is the head page then we have filled
|
|
* the buffer, unless the commit page is still on the
|
|
* reader page.
|
|
*/
|
|
if (rb_is_head_page(next_page, &tail_page->list)) {
|
|
|
|
/*
|
|
* If the commit is not on the reader page, then
|
|
* move the header page.
|
|
*/
|
|
if (!rb_is_reader_page(cpu_buffer->commit_page)) {
|
|
/*
|
|
* If we are not in overwrite mode,
|
|
* this is easy, just stop here.
|
|
*/
|
|
if (!(buffer->flags & RB_FL_OVERWRITE)) {
|
|
local_inc(&cpu_buffer->dropped_events);
|
|
goto out_reset;
|
|
}
|
|
|
|
ret = rb_handle_head_page(cpu_buffer,
|
|
tail_page,
|
|
next_page);
|
|
if (ret < 0)
|
|
goto out_reset;
|
|
if (ret)
|
|
goto out_again;
|
|
} else {
|
|
/*
|
|
* We need to be careful here too. The
|
|
* commit page could still be on the reader
|
|
* page. We could have a small buffer, and
|
|
* have filled up the buffer with events
|
|
* from interrupts and such, and wrapped.
|
|
*
|
|
* Note, if the tail page is also on the
|
|
* reader_page, we let it move out.
|
|
*/
|
|
if (unlikely((cpu_buffer->commit_page !=
|
|
cpu_buffer->tail_page) &&
|
|
(cpu_buffer->commit_page ==
|
|
cpu_buffer->reader_page))) {
|
|
local_inc(&cpu_buffer->commit_overrun);
|
|
goto out_reset;
|
|
}
|
|
}
|
|
}
|
|
|
|
rb_tail_page_update(cpu_buffer, tail_page, next_page);
|
|
|
|
out_again:
|
|
|
|
rb_reset_tail(cpu_buffer, tail, info);
|
|
|
|
/* Commit what we have for now. */
|
|
rb_end_commit(cpu_buffer);
|
|
/* rb_end_commit() decs committing */
|
|
local_inc(&cpu_buffer->committing);
|
|
|
|
/* fail and let the caller try again */
|
|
return ERR_PTR(-EAGAIN);
|
|
|
|
out_reset:
|
|
/* reset write */
|
|
rb_reset_tail(cpu_buffer, tail, info);
|
|
|
|
return NULL;
|
|
}
|
|
|
|
/* Slow path */
|
|
static struct ring_buffer_event *
|
|
rb_add_time_stamp(struct ring_buffer_per_cpu *cpu_buffer,
|
|
struct ring_buffer_event *event, u64 delta, bool abs)
|
|
{
|
|
if (abs)
|
|
event->type_len = RINGBUF_TYPE_TIME_STAMP;
|
|
else
|
|
event->type_len = RINGBUF_TYPE_TIME_EXTEND;
|
|
|
|
/* Not the first event on the page, or not delta? */
|
|
if (abs || rb_event_index(cpu_buffer, event)) {
|
|
event->time_delta = delta & TS_MASK;
|
|
event->array[0] = delta >> TS_SHIFT;
|
|
} else {
|
|
/* nope, just zero it */
|
|
event->time_delta = 0;
|
|
event->array[0] = 0;
|
|
}
|
|
|
|
return skip_time_extend(event);
|
|
}
|
|
|
|
#ifndef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
|
|
static inline bool sched_clock_stable(void)
|
|
{
|
|
return true;
|
|
}
|
|
#endif
|
|
|
|
static void
|
|
rb_check_timestamp(struct ring_buffer_per_cpu *cpu_buffer,
|
|
struct rb_event_info *info)
|
|
{
|
|
u64 write_stamp;
|
|
|
|
WARN_ONCE(1, "Delta way too big! %llu ts=%llu before=%llu after=%llu write stamp=%llu\n%s",
|
|
(unsigned long long)info->delta,
|
|
(unsigned long long)info->ts,
|
|
(unsigned long long)info->before,
|
|
(unsigned long long)info->after,
|
|
(unsigned long long)({rb_time_read(&cpu_buffer->write_stamp, &write_stamp); write_stamp;}),
|
|
sched_clock_stable() ? "" :
|
|
"If you just came from a suspend/resume,\n"
|
|
"please switch to the trace global clock:\n"
|
|
" echo global > /sys/kernel/tracing/trace_clock\n"
|
|
"or add trace_clock=global to the kernel command line\n");
|
|
}
|
|
|
|
static void rb_add_timestamp(struct ring_buffer_per_cpu *cpu_buffer,
|
|
struct ring_buffer_event **event,
|
|
struct rb_event_info *info,
|
|
u64 *delta,
|
|
unsigned int *length)
|
|
{
|
|
bool abs = info->add_timestamp &
|
|
(RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE);
|
|
|
|
if (unlikely(info->delta > (1ULL << 59))) {
|
|
/*
|
|
* Some timers can use more than 59 bits, and when a timestamp
|
|
* is added to the buffer, it will lose those bits.
|
|
*/
|
|
if (abs && (info->ts & TS_MSB)) {
|
|
info->delta &= ABS_TS_MASK;
|
|
|
|
/* did the clock go backwards */
|
|
} else if (info->before == info->after && info->before > info->ts) {
|
|
/* not interrupted */
|
|
static int once;
|
|
|
|
/*
|
|
* This is possible with a recalibrating of the TSC.
|
|
* Do not produce a call stack, but just report it.
|
|
*/
|
|
if (!once) {
|
|
once++;
|
|
pr_warn("Ring buffer clock went backwards: %llu -> %llu\n",
|
|
info->before, info->ts);
|
|
}
|
|
} else
|
|
rb_check_timestamp(cpu_buffer, info);
|
|
if (!abs)
|
|
info->delta = 0;
|
|
}
|
|
*event = rb_add_time_stamp(cpu_buffer, *event, info->delta, abs);
|
|
*length -= RB_LEN_TIME_EXTEND;
|
|
*delta = 0;
|
|
}
|
|
|
|
/**
|
|
* rb_update_event - update event type and data
|
|
* @cpu_buffer: The per cpu buffer of the @event
|
|
* @event: the event to update
|
|
* @info: The info to update the @event with (contains length and delta)
|
|
*
|
|
* Update the type and data fields of the @event. The length
|
|
* is the actual size that is written to the ring buffer,
|
|
* and with this, we can determine what to place into the
|
|
* data field.
|
|
*/
|
|
static void
|
|
rb_update_event(struct ring_buffer_per_cpu *cpu_buffer,
|
|
struct ring_buffer_event *event,
|
|
struct rb_event_info *info)
|
|
{
|
|
unsigned length = info->length;
|
|
u64 delta = info->delta;
|
|
unsigned int nest = local_read(&cpu_buffer->committing) - 1;
|
|
|
|
if (!WARN_ON_ONCE(nest >= MAX_NEST))
|
|
cpu_buffer->event_stamp[nest] = info->ts;
|
|
|
|
/*
|
|
* If we need to add a timestamp, then we
|
|
* add it to the start of the reserved space.
|
|
*/
|
|
if (unlikely(info->add_timestamp))
|
|
rb_add_timestamp(cpu_buffer, &event, info, &delta, &length);
|
|
|
|
event->time_delta = delta;
|
|
length -= RB_EVNT_HDR_SIZE;
|
|
if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT) {
|
|
event->type_len = 0;
|
|
event->array[0] = length;
|
|
} else
|
|
event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT);
|
|
}
|
|
|
|
static unsigned rb_calculate_event_length(unsigned length)
|
|
{
|
|
struct ring_buffer_event event; /* Used only for sizeof array */
|
|
|
|
/* zero length can cause confusions */
|
|
if (!length)
|
|
length++;
|
|
|
|
if (length > RB_MAX_SMALL_DATA || RB_FORCE_8BYTE_ALIGNMENT)
|
|
length += sizeof(event.array[0]);
|
|
|
|
length += RB_EVNT_HDR_SIZE;
|
|
length = ALIGN(length, RB_ARCH_ALIGNMENT);
|
|
|
|
/*
|
|
* In case the time delta is larger than the 27 bits for it
|
|
* in the header, we need to add a timestamp. If another
|
|
* event comes in when trying to discard this one to increase
|
|
* the length, then the timestamp will be added in the allocated
|
|
* space of this event. If length is bigger than the size needed
|
|
* for the TIME_EXTEND, then padding has to be used. The events
|
|
* length must be either RB_LEN_TIME_EXTEND, or greater than or equal
|
|
* to RB_LEN_TIME_EXTEND + 8, as 8 is the minimum size for padding.
|
|
* As length is a multiple of 4, we only need to worry if it
|
|
* is 12 (RB_LEN_TIME_EXTEND + 4).
|
|
*/
|
|
if (length == RB_LEN_TIME_EXTEND + RB_ALIGNMENT)
|
|
length += RB_ALIGNMENT;
|
|
|
|
return length;
|
|
}
|
|
|
|
static inline bool
|
|
rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer,
|
|
struct ring_buffer_event *event)
|
|
{
|
|
unsigned long new_index, old_index;
|
|
struct buffer_page *bpage;
|
|
unsigned long addr;
|
|
|
|
new_index = rb_event_index(cpu_buffer, event);
|
|
old_index = new_index + rb_event_ts_length(event);
|
|
addr = (unsigned long)event;
|
|
addr &= ~((PAGE_SIZE << cpu_buffer->buffer->subbuf_order) - 1);
|
|
|
|
bpage = READ_ONCE(cpu_buffer->tail_page);
|
|
|
|
/*
|
|
* Make sure the tail_page is still the same and
|
|
* the next write location is the end of this event
|
|
*/
|
|
if (bpage->page == (void *)addr && rb_page_write(bpage) == old_index) {
|
|
unsigned long write_mask =
|
|
local_read(&bpage->write) & ~RB_WRITE_MASK;
|
|
unsigned long event_length = rb_event_length(event);
|
|
|
|
/*
|
|
* For the before_stamp to be different than the write_stamp
|
|
* to make sure that the next event adds an absolute
|
|
* value and does not rely on the saved write stamp, which
|
|
* is now going to be bogus.
|
|
*
|
|
* By setting the before_stamp to zero, the next event
|
|
* is not going to use the write_stamp and will instead
|
|
* create an absolute timestamp. This means there's no
|
|
* reason to update the wirte_stamp!
|
|
*/
|
|
rb_time_set(&cpu_buffer->before_stamp, 0);
|
|
|
|
/*
|
|
* If an event were to come in now, it would see that the
|
|
* write_stamp and the before_stamp are different, and assume
|
|
* that this event just added itself before updating
|
|
* the write stamp. The interrupting event will fix the
|
|
* write stamp for us, and use an absolute timestamp.
|
|
*/
|
|
|
|
/*
|
|
* This is on the tail page. It is possible that
|
|
* a write could come in and move the tail page
|
|
* and write to the next page. That is fine
|
|
* because we just shorten what is on this page.
|
|
*/
|
|
old_index += write_mask;
|
|
new_index += write_mask;
|
|
|
|
/* caution: old_index gets updated on cmpxchg failure */
|
|
if (local_try_cmpxchg(&bpage->write, &old_index, new_index)) {
|
|
/* update counters */
|
|
local_sub(event_length, &cpu_buffer->entries_bytes);
|
|
return true;
|
|
}
|
|
}
|
|
|
|
/* could not discard */
|
|
return false;
|
|
}
|
|
|
|
static void rb_start_commit(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
local_inc(&cpu_buffer->committing);
|
|
local_inc(&cpu_buffer->commits);
|
|
}
|
|
|
|
static __always_inline void
|
|
rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
unsigned long max_count;
|
|
|
|
/*
|
|
* We only race with interrupts and NMIs on this CPU.
|
|
* If we own the commit event, then we can commit
|
|
* all others that interrupted us, since the interruptions
|
|
* are in stack format (they finish before they come
|
|
* back to us). This allows us to do a simple loop to
|
|
* assign the commit to the tail.
|
|
*/
|
|
again:
|
|
max_count = cpu_buffer->nr_pages * 100;
|
|
|
|
while (cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)) {
|
|
if (RB_WARN_ON(cpu_buffer, !(--max_count)))
|
|
return;
|
|
if (RB_WARN_ON(cpu_buffer,
|
|
rb_is_reader_page(cpu_buffer->tail_page)))
|
|
return;
|
|
/*
|
|
* No need for a memory barrier here, as the update
|
|
* of the tail_page did it for this page.
|
|
*/
|
|
local_set(&cpu_buffer->commit_page->page->commit,
|
|
rb_page_write(cpu_buffer->commit_page));
|
|
rb_inc_page(&cpu_buffer->commit_page);
|
|
/* add barrier to keep gcc from optimizing too much */
|
|
barrier();
|
|
}
|
|
while (rb_commit_index(cpu_buffer) !=
|
|
rb_page_write(cpu_buffer->commit_page)) {
|
|
|
|
/* Make sure the readers see the content of what is committed. */
|
|
smp_wmb();
|
|
local_set(&cpu_buffer->commit_page->page->commit,
|
|
rb_page_write(cpu_buffer->commit_page));
|
|
RB_WARN_ON(cpu_buffer,
|
|
local_read(&cpu_buffer->commit_page->page->commit) &
|
|
~RB_WRITE_MASK);
|
|
barrier();
|
|
}
|
|
|
|
/* again, keep gcc from optimizing */
|
|
barrier();
|
|
|
|
/*
|
|
* If an interrupt came in just after the first while loop
|
|
* and pushed the tail page forward, we will be left with
|
|
* a dangling commit that will never go forward.
|
|
*/
|
|
if (unlikely(cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)))
|
|
goto again;
|
|
}
|
|
|
|
static __always_inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
unsigned long commits;
|
|
|
|
if (RB_WARN_ON(cpu_buffer,
|
|
!local_read(&cpu_buffer->committing)))
|
|
return;
|
|
|
|
again:
|
|
commits = local_read(&cpu_buffer->commits);
|
|
/* synchronize with interrupts */
|
|
barrier();
|
|
if (local_read(&cpu_buffer->committing) == 1)
|
|
rb_set_commit_to_write(cpu_buffer);
|
|
|
|
local_dec(&cpu_buffer->committing);
|
|
|
|
/* synchronize with interrupts */
|
|
barrier();
|
|
|
|
/*
|
|
* Need to account for interrupts coming in between the
|
|
* updating of the commit page and the clearing of the
|
|
* committing counter.
|
|
*/
|
|
if (unlikely(local_read(&cpu_buffer->commits) != commits) &&
|
|
!local_read(&cpu_buffer->committing)) {
|
|
local_inc(&cpu_buffer->committing);
|
|
goto again;
|
|
}
|
|
}
|
|
|
|
static inline void rb_event_discard(struct ring_buffer_event *event)
|
|
{
|
|
if (extended_time(event))
|
|
event = skip_time_extend(event);
|
|
|
|
/* array[0] holds the actual length for the discarded event */
|
|
event->array[0] = rb_event_data_length(event) - RB_EVNT_HDR_SIZE;
|
|
event->type_len = RINGBUF_TYPE_PADDING;
|
|
/* time delta must be non zero */
|
|
if (!event->time_delta)
|
|
event->time_delta = 1;
|
|
}
|
|
|
|
static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
local_inc(&cpu_buffer->entries);
|
|
rb_end_commit(cpu_buffer);
|
|
}
|
|
|
|
static __always_inline void
|
|
rb_wakeups(struct trace_buffer *buffer, struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
if (buffer->irq_work.waiters_pending) {
|
|
buffer->irq_work.waiters_pending = false;
|
|
/* irq_work_queue() supplies it's own memory barriers */
|
|
irq_work_queue(&buffer->irq_work.work);
|
|
}
|
|
|
|
if (cpu_buffer->irq_work.waiters_pending) {
|
|
cpu_buffer->irq_work.waiters_pending = false;
|
|
/* irq_work_queue() supplies it's own memory barriers */
|
|
irq_work_queue(&cpu_buffer->irq_work.work);
|
|
}
|
|
|
|
if (cpu_buffer->last_pages_touch == local_read(&cpu_buffer->pages_touched))
|
|
return;
|
|
|
|
if (cpu_buffer->reader_page == cpu_buffer->commit_page)
|
|
return;
|
|
|
|
if (!cpu_buffer->irq_work.full_waiters_pending)
|
|
return;
|
|
|
|
cpu_buffer->last_pages_touch = local_read(&cpu_buffer->pages_touched);
|
|
|
|
if (!full_hit(buffer, cpu_buffer->cpu, cpu_buffer->shortest_full))
|
|
return;
|
|
|
|
cpu_buffer->irq_work.wakeup_full = true;
|
|
cpu_buffer->irq_work.full_waiters_pending = false;
|
|
/* irq_work_queue() supplies it's own memory barriers */
|
|
irq_work_queue(&cpu_buffer->irq_work.work);
|
|
}
|
|
|
|
#ifdef CONFIG_RING_BUFFER_RECORD_RECURSION
|
|
# define do_ring_buffer_record_recursion() \
|
|
do_ftrace_record_recursion(_THIS_IP_, _RET_IP_)
|
|
#else
|
|
# define do_ring_buffer_record_recursion() do { } while (0)
|
|
#endif
|
|
|
|
/*
|
|
* The lock and unlock are done within a preempt disable section.
|
|
* The current_context per_cpu variable can only be modified
|
|
* by the current task between lock and unlock. But it can
|
|
* be modified more than once via an interrupt. To pass this
|
|
* information from the lock to the unlock without having to
|
|
* access the 'in_interrupt()' functions again (which do show
|
|
* a bit of overhead in something as critical as function tracing,
|
|
* we use a bitmask trick.
|
|
*
|
|
* bit 1 = NMI context
|
|
* bit 2 = IRQ context
|
|
* bit 3 = SoftIRQ context
|
|
* bit 4 = normal context.
|
|
*
|
|
* This works because this is the order of contexts that can
|
|
* preempt other contexts. A SoftIRQ never preempts an IRQ
|
|
* context.
|
|
*
|
|
* When the context is determined, the corresponding bit is
|
|
* checked and set (if it was set, then a recursion of that context
|
|
* happened).
|
|
*
|
|
* On unlock, we need to clear this bit. To do so, just subtract
|
|
* 1 from the current_context and AND it to itself.
|
|
*
|
|
* (binary)
|
|
* 101 - 1 = 100
|
|
* 101 & 100 = 100 (clearing bit zero)
|
|
*
|
|
* 1010 - 1 = 1001
|
|
* 1010 & 1001 = 1000 (clearing bit 1)
|
|
*
|
|
* The least significant bit can be cleared this way, and it
|
|
* just so happens that it is the same bit corresponding to
|
|
* the current context.
|
|
*
|
|
* Now the TRANSITION bit breaks the above slightly. The TRANSITION bit
|
|
* is set when a recursion is detected at the current context, and if
|
|
* the TRANSITION bit is already set, it will fail the recursion.
|
|
* This is needed because there's a lag between the changing of
|
|
* interrupt context and updating the preempt count. In this case,
|
|
* a false positive will be found. To handle this, one extra recursion
|
|
* is allowed, and this is done by the TRANSITION bit. If the TRANSITION
|
|
* bit is already set, then it is considered a recursion and the function
|
|
* ends. Otherwise, the TRANSITION bit is set, and that bit is returned.
|
|
*
|
|
* On the trace_recursive_unlock(), the TRANSITION bit will be the first
|
|
* to be cleared. Even if it wasn't the context that set it. That is,
|
|
* if an interrupt comes in while NORMAL bit is set and the ring buffer
|
|
* is called before preempt_count() is updated, since the check will
|
|
* be on the NORMAL bit, the TRANSITION bit will then be set. If an
|
|
* NMI then comes in, it will set the NMI bit, but when the NMI code
|
|
* does the trace_recursive_unlock() it will clear the TRANSITION bit
|
|
* and leave the NMI bit set. But this is fine, because the interrupt
|
|
* code that set the TRANSITION bit will then clear the NMI bit when it
|
|
* calls trace_recursive_unlock(). If another NMI comes in, it will
|
|
* set the TRANSITION bit and continue.
|
|
*
|
|
* Note: The TRANSITION bit only handles a single transition between context.
|
|
*/
|
|
|
|
static __always_inline bool
|
|
trace_recursive_lock(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
unsigned int val = cpu_buffer->current_context;
|
|
int bit = interrupt_context_level();
|
|
|
|
bit = RB_CTX_NORMAL - bit;
|
|
|
|
if (unlikely(val & (1 << (bit + cpu_buffer->nest)))) {
|
|
/*
|
|
* It is possible that this was called by transitioning
|
|
* between interrupt context, and preempt_count() has not
|
|
* been updated yet. In this case, use the TRANSITION bit.
|
|
*/
|
|
bit = RB_CTX_TRANSITION;
|
|
if (val & (1 << (bit + cpu_buffer->nest))) {
|
|
do_ring_buffer_record_recursion();
|
|
return true;
|
|
}
|
|
}
|
|
|
|
val |= (1 << (bit + cpu_buffer->nest));
|
|
cpu_buffer->current_context = val;
|
|
|
|
return false;
|
|
}
|
|
|
|
static __always_inline void
|
|
trace_recursive_unlock(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
cpu_buffer->current_context &=
|
|
cpu_buffer->current_context - (1 << cpu_buffer->nest);
|
|
}
|
|
|
|
/* The recursive locking above uses 5 bits */
|
|
#define NESTED_BITS 5
|
|
|
|
/**
|
|
* ring_buffer_nest_start - Allow to trace while nested
|
|
* @buffer: The ring buffer to modify
|
|
*
|
|
* The ring buffer has a safety mechanism to prevent recursion.
|
|
* But there may be a case where a trace needs to be done while
|
|
* tracing something else. In this case, calling this function
|
|
* will allow this function to nest within a currently active
|
|
* ring_buffer_lock_reserve().
|
|
*
|
|
* Call this function before calling another ring_buffer_lock_reserve() and
|
|
* call ring_buffer_nest_end() after the nested ring_buffer_unlock_commit().
|
|
*/
|
|
void ring_buffer_nest_start(struct trace_buffer *buffer)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
int cpu;
|
|
|
|
/* Enabled by ring_buffer_nest_end() */
|
|
preempt_disable_notrace();
|
|
cpu = raw_smp_processor_id();
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
/* This is the shift value for the above recursive locking */
|
|
cpu_buffer->nest += NESTED_BITS;
|
|
}
|
|
|
|
/**
|
|
* ring_buffer_nest_end - Allow to trace while nested
|
|
* @buffer: The ring buffer to modify
|
|
*
|
|
* Must be called after ring_buffer_nest_start() and after the
|
|
* ring_buffer_unlock_commit().
|
|
*/
|
|
void ring_buffer_nest_end(struct trace_buffer *buffer)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
int cpu;
|
|
|
|
/* disabled by ring_buffer_nest_start() */
|
|
cpu = raw_smp_processor_id();
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
/* This is the shift value for the above recursive locking */
|
|
cpu_buffer->nest -= NESTED_BITS;
|
|
preempt_enable_notrace();
|
|
}
|
|
|
|
/**
|
|
* ring_buffer_unlock_commit - commit a reserved
|
|
* @buffer: The buffer to commit to
|
|
*
|
|
* This commits the data to the ring buffer, and releases any locks held.
|
|
*
|
|
* Must be paired with ring_buffer_lock_reserve.
|
|
*/
|
|
int ring_buffer_unlock_commit(struct trace_buffer *buffer)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
int cpu = raw_smp_processor_id();
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
|
|
rb_commit(cpu_buffer);
|
|
|
|
rb_wakeups(buffer, cpu_buffer);
|
|
|
|
trace_recursive_unlock(cpu_buffer);
|
|
|
|
preempt_enable_notrace();
|
|
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit);
|
|
|
|
/* Special value to validate all deltas on a page. */
|
|
#define CHECK_FULL_PAGE 1L
|
|
|
|
#ifdef CONFIG_RING_BUFFER_VALIDATE_TIME_DELTAS
|
|
|
|
static const char *show_irq_str(int bits)
|
|
{
|
|
const char *type[] = {
|
|
".", // 0
|
|
"s", // 1
|
|
"h", // 2
|
|
"Hs", // 3
|
|
"n", // 4
|
|
"Ns", // 5
|
|
"Nh", // 6
|
|
"NHs", // 7
|
|
};
|
|
|
|
return type[bits];
|
|
}
|
|
|
|
/* Assume this is an trace event */
|
|
static const char *show_flags(struct ring_buffer_event *event)
|
|
{
|
|
struct trace_entry *entry;
|
|
int bits = 0;
|
|
|
|
if (rb_event_data_length(event) - RB_EVNT_HDR_SIZE < sizeof(*entry))
|
|
return "X";
|
|
|
|
entry = ring_buffer_event_data(event);
|
|
|
|
if (entry->flags & TRACE_FLAG_SOFTIRQ)
|
|
bits |= 1;
|
|
|
|
if (entry->flags & TRACE_FLAG_HARDIRQ)
|
|
bits |= 2;
|
|
|
|
if (entry->flags & TRACE_FLAG_NMI)
|
|
bits |= 4;
|
|
|
|
return show_irq_str(bits);
|
|
}
|
|
|
|
static const char *show_irq(struct ring_buffer_event *event)
|
|
{
|
|
struct trace_entry *entry;
|
|
|
|
if (rb_event_data_length(event) - RB_EVNT_HDR_SIZE < sizeof(*entry))
|
|
return "";
|
|
|
|
entry = ring_buffer_event_data(event);
|
|
if (entry->flags & TRACE_FLAG_IRQS_OFF)
|
|
return "d";
|
|
return "";
|
|
}
|
|
|
|
static const char *show_interrupt_level(void)
|
|
{
|
|
unsigned long pc = preempt_count();
|
|
unsigned char level = 0;
|
|
|
|
if (pc & SOFTIRQ_OFFSET)
|
|
level |= 1;
|
|
|
|
if (pc & HARDIRQ_MASK)
|
|
level |= 2;
|
|
|
|
if (pc & NMI_MASK)
|
|
level |= 4;
|
|
|
|
return show_irq_str(level);
|
|
}
|
|
|
|
static void dump_buffer_page(struct buffer_data_page *bpage,
|
|
struct rb_event_info *info,
|
|
unsigned long tail)
|
|
{
|
|
struct ring_buffer_event *event;
|
|
u64 ts, delta;
|
|
int e;
|
|
|
|
ts = bpage->time_stamp;
|
|
pr_warn(" [%lld] PAGE TIME STAMP\n", ts);
|
|
|
|
for (e = 0; e < tail; e += rb_event_length(event)) {
|
|
|
|
event = (struct ring_buffer_event *)(bpage->data + e);
|
|
|
|
switch (event->type_len) {
|
|
|
|
case RINGBUF_TYPE_TIME_EXTEND:
|
|
delta = rb_event_time_stamp(event);
|
|
ts += delta;
|
|
pr_warn(" 0x%x: [%lld] delta:%lld TIME EXTEND\n",
|
|
e, ts, delta);
|
|
break;
|
|
|
|
case RINGBUF_TYPE_TIME_STAMP:
|
|
delta = rb_event_time_stamp(event);
|
|
ts = rb_fix_abs_ts(delta, ts);
|
|
pr_warn(" 0x%x: [%lld] absolute:%lld TIME STAMP\n",
|
|
e, ts, delta);
|
|
break;
|
|
|
|
case RINGBUF_TYPE_PADDING:
|
|
ts += event->time_delta;
|
|
pr_warn(" 0x%x: [%lld] delta:%d PADDING\n",
|
|
e, ts, event->time_delta);
|
|
break;
|
|
|
|
case RINGBUF_TYPE_DATA:
|
|
ts += event->time_delta;
|
|
pr_warn(" 0x%x: [%lld] delta:%d %s%s\n",
|
|
e, ts, event->time_delta,
|
|
show_flags(event), show_irq(event));
|
|
break;
|
|
|
|
default:
|
|
break;
|
|
}
|
|
}
|
|
pr_warn("expected end:0x%lx last event actually ended at:0x%x\n", tail, e);
|
|
}
|
|
|
|
static DEFINE_PER_CPU(atomic_t, checking);
|
|
static atomic_t ts_dump;
|
|
|
|
#define buffer_warn_return(fmt, ...) \
|
|
do { \
|
|
/* If another report is happening, ignore this one */ \
|
|
if (atomic_inc_return(&ts_dump) != 1) { \
|
|
atomic_dec(&ts_dump); \
|
|
goto out; \
|
|
} \
|
|
atomic_inc(&cpu_buffer->record_disabled); \
|
|
pr_warn(fmt, ##__VA_ARGS__); \
|
|
dump_buffer_page(bpage, info, tail); \
|
|
atomic_dec(&ts_dump); \
|
|
/* There's some cases in boot up that this can happen */ \
|
|
if (WARN_ON_ONCE(system_state != SYSTEM_BOOTING)) \
|
|
/* Do not re-enable checking */ \
|
|
return; \
|
|
} while (0)
|
|
|
|
/*
|
|
* Check if the current event time stamp matches the deltas on
|
|
* the buffer page.
|
|
*/
|
|
static void check_buffer(struct ring_buffer_per_cpu *cpu_buffer,
|
|
struct rb_event_info *info,
|
|
unsigned long tail)
|
|
{
|
|
struct ring_buffer_event *event;
|
|
struct buffer_data_page *bpage;
|
|
u64 ts, delta;
|
|
bool full = false;
|
|
int e;
|
|
|
|
bpage = info->tail_page->page;
|
|
|
|
if (tail == CHECK_FULL_PAGE) {
|
|
full = true;
|
|
tail = local_read(&bpage->commit);
|
|
} else if (info->add_timestamp &
|
|
(RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE)) {
|
|
/* Ignore events with absolute time stamps */
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* Do not check the first event (skip possible extends too).
|
|
* Also do not check if previous events have not been committed.
|
|
*/
|
|
if (tail <= 8 || tail > local_read(&bpage->commit))
|
|
return;
|
|
|
|
/*
|
|
* If this interrupted another event,
|
|
*/
|
|
if (atomic_inc_return(this_cpu_ptr(&checking)) != 1)
|
|
goto out;
|
|
|
|
ts = bpage->time_stamp;
|
|
|
|
for (e = 0; e < tail; e += rb_event_length(event)) {
|
|
|
|
event = (struct ring_buffer_event *)(bpage->data + e);
|
|
|
|
switch (event->type_len) {
|
|
|
|
case RINGBUF_TYPE_TIME_EXTEND:
|
|
delta = rb_event_time_stamp(event);
|
|
ts += delta;
|
|
break;
|
|
|
|
case RINGBUF_TYPE_TIME_STAMP:
|
|
delta = rb_event_time_stamp(event);
|
|
delta = rb_fix_abs_ts(delta, ts);
|
|
if (delta < ts) {
|
|
buffer_warn_return("[CPU: %d]ABSOLUTE TIME WENT BACKWARDS: last ts: %lld absolute ts: %lld\n",
|
|
cpu_buffer->cpu, ts, delta);
|
|
}
|
|
ts = delta;
|
|
break;
|
|
|
|
case RINGBUF_TYPE_PADDING:
|
|
if (event->time_delta == 1)
|
|
break;
|
|
fallthrough;
|
|
case RINGBUF_TYPE_DATA:
|
|
ts += event->time_delta;
|
|
break;
|
|
|
|
default:
|
|
RB_WARN_ON(cpu_buffer, 1);
|
|
}
|
|
}
|
|
if ((full && ts > info->ts) ||
|
|
(!full && ts + info->delta != info->ts)) {
|
|
buffer_warn_return("[CPU: %d]TIME DOES NOT MATCH expected:%lld actual:%lld delta:%lld before:%lld after:%lld%s context:%s\n",
|
|
cpu_buffer->cpu,
|
|
ts + info->delta, info->ts, info->delta,
|
|
info->before, info->after,
|
|
full ? " (full)" : "", show_interrupt_level());
|
|
}
|
|
out:
|
|
atomic_dec(this_cpu_ptr(&checking));
|
|
}
|
|
#else
|
|
static inline void check_buffer(struct ring_buffer_per_cpu *cpu_buffer,
|
|
struct rb_event_info *info,
|
|
unsigned long tail)
|
|
{
|
|
}
|
|
#endif /* CONFIG_RING_BUFFER_VALIDATE_TIME_DELTAS */
|
|
|
|
static struct ring_buffer_event *
|
|
__rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
|
|
struct rb_event_info *info)
|
|
{
|
|
struct ring_buffer_event *event;
|
|
struct buffer_page *tail_page;
|
|
unsigned long tail, write, w;
|
|
|
|
/* Don't let the compiler play games with cpu_buffer->tail_page */
|
|
tail_page = info->tail_page = READ_ONCE(cpu_buffer->tail_page);
|
|
|
|
/*A*/ w = local_read(&tail_page->write) & RB_WRITE_MASK;
|
|
barrier();
|
|
rb_time_read(&cpu_buffer->before_stamp, &info->before);
|
|
rb_time_read(&cpu_buffer->write_stamp, &info->after);
|
|
barrier();
|
|
info->ts = rb_time_stamp(cpu_buffer->buffer);
|
|
|
|
if ((info->add_timestamp & RB_ADD_STAMP_ABSOLUTE)) {
|
|
info->delta = info->ts;
|
|
} else {
|
|
/*
|
|
* If interrupting an event time update, we may need an
|
|
* absolute timestamp.
|
|
* Don't bother if this is the start of a new page (w == 0).
|
|
*/
|
|
if (!w) {
|
|
/* Use the sub-buffer timestamp */
|
|
info->delta = 0;
|
|
} else if (unlikely(info->before != info->after)) {
|
|
info->add_timestamp |= RB_ADD_STAMP_FORCE | RB_ADD_STAMP_EXTEND;
|
|
info->length += RB_LEN_TIME_EXTEND;
|
|
} else {
|
|
info->delta = info->ts - info->after;
|
|
if (unlikely(test_time_stamp(info->delta))) {
|
|
info->add_timestamp |= RB_ADD_STAMP_EXTEND;
|
|
info->length += RB_LEN_TIME_EXTEND;
|
|
}
|
|
}
|
|
}
|
|
|
|
/*B*/ rb_time_set(&cpu_buffer->before_stamp, info->ts);
|
|
|
|
/*C*/ write = local_add_return(info->length, &tail_page->write);
|
|
|
|
/* set write to only the index of the write */
|
|
write &= RB_WRITE_MASK;
|
|
|
|
tail = write - info->length;
|
|
|
|
/* See if we shot pass the end of this buffer page */
|
|
if (unlikely(write > cpu_buffer->buffer->subbuf_size)) {
|
|
check_buffer(cpu_buffer, info, CHECK_FULL_PAGE);
|
|
return rb_move_tail(cpu_buffer, tail, info);
|
|
}
|
|
|
|
if (likely(tail == w)) {
|
|
/* Nothing interrupted us between A and C */
|
|
/*D*/ rb_time_set(&cpu_buffer->write_stamp, info->ts);
|
|
/*
|
|
* If something came in between C and D, the write stamp
|
|
* may now not be in sync. But that's fine as the before_stamp
|
|
* will be different and then next event will just be forced
|
|
* to use an absolute timestamp.
|
|
*/
|
|
if (likely(!(info->add_timestamp &
|
|
(RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE))))
|
|
/* This did not interrupt any time update */
|
|
info->delta = info->ts - info->after;
|
|
else
|
|
/* Just use full timestamp for interrupting event */
|
|
info->delta = info->ts;
|
|
check_buffer(cpu_buffer, info, tail);
|
|
} else {
|
|
u64 ts;
|
|
/* SLOW PATH - Interrupted between A and C */
|
|
|
|
/* Save the old before_stamp */
|
|
rb_time_read(&cpu_buffer->before_stamp, &info->before);
|
|
|
|
/*
|
|
* Read a new timestamp and update the before_stamp to make
|
|
* the next event after this one force using an absolute
|
|
* timestamp. This is in case an interrupt were to come in
|
|
* between E and F.
|
|
*/
|
|
ts = rb_time_stamp(cpu_buffer->buffer);
|
|
rb_time_set(&cpu_buffer->before_stamp, ts);
|
|
|
|
barrier();
|
|
/*E*/ rb_time_read(&cpu_buffer->write_stamp, &info->after);
|
|
barrier();
|
|
/*F*/ if (write == (local_read(&tail_page->write) & RB_WRITE_MASK) &&
|
|
info->after == info->before && info->after < ts) {
|
|
/*
|
|
* Nothing came after this event between C and F, it is
|
|
* safe to use info->after for the delta as it
|
|
* matched info->before and is still valid.
|
|
*/
|
|
info->delta = ts - info->after;
|
|
} else {
|
|
/*
|
|
* Interrupted between C and F:
|
|
* Lost the previous events time stamp. Just set the
|
|
* delta to zero, and this will be the same time as
|
|
* the event this event interrupted. And the events that
|
|
* came after this will still be correct (as they would
|
|
* have built their delta on the previous event.
|
|
*/
|
|
info->delta = 0;
|
|
}
|
|
info->ts = ts;
|
|
info->add_timestamp &= ~RB_ADD_STAMP_FORCE;
|
|
}
|
|
|
|
/*
|
|
* If this is the first commit on the page, then it has the same
|
|
* timestamp as the page itself.
|
|
*/
|
|
if (unlikely(!tail && !(info->add_timestamp &
|
|
(RB_ADD_STAMP_FORCE | RB_ADD_STAMP_ABSOLUTE))))
|
|
info->delta = 0;
|
|
|
|
/* We reserved something on the buffer */
|
|
|
|
event = __rb_page_index(tail_page, tail);
|
|
rb_update_event(cpu_buffer, event, info);
|
|
|
|
local_inc(&tail_page->entries);
|
|
|
|
/*
|
|
* If this is the first commit on the page, then update
|
|
* its timestamp.
|
|
*/
|
|
if (unlikely(!tail))
|
|
tail_page->page->time_stamp = info->ts;
|
|
|
|
/* account for these added bytes */
|
|
local_add(info->length, &cpu_buffer->entries_bytes);
|
|
|
|
return event;
|
|
}
|
|
|
|
static __always_inline struct ring_buffer_event *
|
|
rb_reserve_next_event(struct trace_buffer *buffer,
|
|
struct ring_buffer_per_cpu *cpu_buffer,
|
|
unsigned long length)
|
|
{
|
|
struct ring_buffer_event *event;
|
|
struct rb_event_info info;
|
|
int nr_loops = 0;
|
|
int add_ts_default;
|
|
|
|
/* ring buffer does cmpxchg, make sure it is safe in NMI context */
|
|
if (!IS_ENABLED(CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG) &&
|
|
(unlikely(in_nmi()))) {
|
|
return NULL;
|
|
}
|
|
|
|
rb_start_commit(cpu_buffer);
|
|
/* The commit page can not change after this */
|
|
|
|
#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
|
|
/*
|
|
* Due to the ability to swap a cpu buffer from a buffer
|
|
* it is possible it was swapped before we committed.
|
|
* (committing stops a swap). We check for it here and
|
|
* if it happened, we have to fail the write.
|
|
*/
|
|
barrier();
|
|
if (unlikely(READ_ONCE(cpu_buffer->buffer) != buffer)) {
|
|
local_dec(&cpu_buffer->committing);
|
|
local_dec(&cpu_buffer->commits);
|
|
return NULL;
|
|
}
|
|
#endif
|
|
|
|
info.length = rb_calculate_event_length(length);
|
|
|
|
if (ring_buffer_time_stamp_abs(cpu_buffer->buffer)) {
|
|
add_ts_default = RB_ADD_STAMP_ABSOLUTE;
|
|
info.length += RB_LEN_TIME_EXTEND;
|
|
if (info.length > cpu_buffer->buffer->max_data_size)
|
|
goto out_fail;
|
|
} else {
|
|
add_ts_default = RB_ADD_STAMP_NONE;
|
|
}
|
|
|
|
again:
|
|
info.add_timestamp = add_ts_default;
|
|
info.delta = 0;
|
|
|
|
/*
|
|
* We allow for interrupts to reenter here and do a trace.
|
|
* If one does, it will cause this original code to loop
|
|
* back here. Even with heavy interrupts happening, this
|
|
* should only happen a few times in a row. If this happens
|
|
* 1000 times in a row, there must be either an interrupt
|
|
* storm or we have something buggy.
|
|
* Bail!
|
|
*/
|
|
if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000))
|
|
goto out_fail;
|
|
|
|
event = __rb_reserve_next(cpu_buffer, &info);
|
|
|
|
if (unlikely(PTR_ERR(event) == -EAGAIN)) {
|
|
if (info.add_timestamp & (RB_ADD_STAMP_FORCE | RB_ADD_STAMP_EXTEND))
|
|
info.length -= RB_LEN_TIME_EXTEND;
|
|
goto again;
|
|
}
|
|
|
|
if (likely(event))
|
|
return event;
|
|
out_fail:
|
|
rb_end_commit(cpu_buffer);
|
|
return NULL;
|
|
}
|
|
|
|
/**
|
|
* ring_buffer_lock_reserve - reserve a part of the buffer
|
|
* @buffer: the ring buffer to reserve from
|
|
* @length: the length of the data to reserve (excluding event header)
|
|
*
|
|
* Returns a reserved event on the ring buffer to copy directly to.
|
|
* The user of this interface will need to get the body to write into
|
|
* and can use the ring_buffer_event_data() interface.
|
|
*
|
|
* The length is the length of the data needed, not the event length
|
|
* which also includes the event header.
|
|
*
|
|
* Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
|
|
* If NULL is returned, then nothing has been allocated or locked.
|
|
*/
|
|
struct ring_buffer_event *
|
|
ring_buffer_lock_reserve(struct trace_buffer *buffer, unsigned long length)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
struct ring_buffer_event *event;
|
|
int cpu;
|
|
|
|
/* If we are tracing schedule, we don't want to recurse */
|
|
preempt_disable_notrace();
|
|
|
|
if (unlikely(atomic_read(&buffer->record_disabled)))
|
|
goto out;
|
|
|
|
cpu = raw_smp_processor_id();
|
|
|
|
if (unlikely(!cpumask_test_cpu(cpu, buffer->cpumask)))
|
|
goto out;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
|
|
if (unlikely(atomic_read(&cpu_buffer->record_disabled)))
|
|
goto out;
|
|
|
|
if (unlikely(length > buffer->max_data_size))
|
|
goto out;
|
|
|
|
if (unlikely(trace_recursive_lock(cpu_buffer)))
|
|
goto out;
|
|
|
|
event = rb_reserve_next_event(buffer, cpu_buffer, length);
|
|
if (!event)
|
|
goto out_unlock;
|
|
|
|
return event;
|
|
|
|
out_unlock:
|
|
trace_recursive_unlock(cpu_buffer);
|
|
out:
|
|
preempt_enable_notrace();
|
|
return NULL;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve);
|
|
|
|
/*
|
|
* Decrement the entries to the page that an event is on.
|
|
* The event does not even need to exist, only the pointer
|
|
* to the page it is on. This may only be called before the commit
|
|
* takes place.
|
|
*/
|
|
static inline void
|
|
rb_decrement_entry(struct ring_buffer_per_cpu *cpu_buffer,
|
|
struct ring_buffer_event *event)
|
|
{
|
|
unsigned long addr = (unsigned long)event;
|
|
struct buffer_page *bpage = cpu_buffer->commit_page;
|
|
struct buffer_page *start;
|
|
|
|
addr &= ~((PAGE_SIZE << cpu_buffer->buffer->subbuf_order) - 1);
|
|
|
|
/* Do the likely case first */
|
|
if (likely(bpage->page == (void *)addr)) {
|
|
local_dec(&bpage->entries);
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* Because the commit page may be on the reader page we
|
|
* start with the next page and check the end loop there.
|
|
*/
|
|
rb_inc_page(&bpage);
|
|
start = bpage;
|
|
do {
|
|
if (bpage->page == (void *)addr) {
|
|
local_dec(&bpage->entries);
|
|
return;
|
|
}
|
|
rb_inc_page(&bpage);
|
|
} while (bpage != start);
|
|
|
|
/* commit not part of this buffer?? */
|
|
RB_WARN_ON(cpu_buffer, 1);
|
|
}
|
|
|
|
/**
|
|
* ring_buffer_discard_commit - discard an event that has not been committed
|
|
* @buffer: the ring buffer
|
|
* @event: non committed event to discard
|
|
*
|
|
* Sometimes an event that is in the ring buffer needs to be ignored.
|
|
* This function lets the user discard an event in the ring buffer
|
|
* and then that event will not be read later.
|
|
*
|
|
* This function only works if it is called before the item has been
|
|
* committed. It will try to free the event from the ring buffer
|
|
* if another event has not been added behind it.
|
|
*
|
|
* If another event has been added behind it, it will set the event
|
|
* up as discarded, and perform the commit.
|
|
*
|
|
* If this function is called, do not call ring_buffer_unlock_commit on
|
|
* the event.
|
|
*/
|
|
void ring_buffer_discard_commit(struct trace_buffer *buffer,
|
|
struct ring_buffer_event *event)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
int cpu;
|
|
|
|
/* The event is discarded regardless */
|
|
rb_event_discard(event);
|
|
|
|
cpu = smp_processor_id();
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
|
|
/*
|
|
* This must only be called if the event has not been
|
|
* committed yet. Thus we can assume that preemption
|
|
* is still disabled.
|
|
*/
|
|
RB_WARN_ON(buffer, !local_read(&cpu_buffer->committing));
|
|
|
|
rb_decrement_entry(cpu_buffer, event);
|
|
if (rb_try_to_discard(cpu_buffer, event))
|
|
goto out;
|
|
|
|
out:
|
|
rb_end_commit(cpu_buffer);
|
|
|
|
trace_recursive_unlock(cpu_buffer);
|
|
|
|
preempt_enable_notrace();
|
|
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_discard_commit);
|
|
|
|
/**
|
|
* ring_buffer_write - write data to the buffer without reserving
|
|
* @buffer: The ring buffer to write to.
|
|
* @length: The length of the data being written (excluding the event header)
|
|
* @data: The data to write to the buffer.
|
|
*
|
|
* This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
|
|
* one function. If you already have the data to write to the buffer, it
|
|
* may be easier to simply call this function.
|
|
*
|
|
* Note, like ring_buffer_lock_reserve, the length is the length of the data
|
|
* and not the length of the event which would hold the header.
|
|
*/
|
|
int ring_buffer_write(struct trace_buffer *buffer,
|
|
unsigned long length,
|
|
void *data)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
struct ring_buffer_event *event;
|
|
void *body;
|
|
int ret = -EBUSY;
|
|
int cpu;
|
|
|
|
preempt_disable_notrace();
|
|
|
|
if (atomic_read(&buffer->record_disabled))
|
|
goto out;
|
|
|
|
cpu = raw_smp_processor_id();
|
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
goto out;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
|
|
if (atomic_read(&cpu_buffer->record_disabled))
|
|
goto out;
|
|
|
|
if (length > buffer->max_data_size)
|
|
goto out;
|
|
|
|
if (unlikely(trace_recursive_lock(cpu_buffer)))
|
|
goto out;
|
|
|
|
event = rb_reserve_next_event(buffer, cpu_buffer, length);
|
|
if (!event)
|
|
goto out_unlock;
|
|
|
|
body = rb_event_data(event);
|
|
|
|
memcpy(body, data, length);
|
|
|
|
rb_commit(cpu_buffer);
|
|
|
|
rb_wakeups(buffer, cpu_buffer);
|
|
|
|
ret = 0;
|
|
|
|
out_unlock:
|
|
trace_recursive_unlock(cpu_buffer);
|
|
|
|
out:
|
|
preempt_enable_notrace();
|
|
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_write);
|
|
|
|
static bool rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
struct buffer_page *reader = cpu_buffer->reader_page;
|
|
struct buffer_page *head = rb_set_head_page(cpu_buffer);
|
|
struct buffer_page *commit = cpu_buffer->commit_page;
|
|
|
|
/* In case of error, head will be NULL */
|
|
if (unlikely(!head))
|
|
return true;
|
|
|
|
/* Reader should exhaust content in reader page */
|
|
if (reader->read != rb_page_size(reader))
|
|
return false;
|
|
|
|
/*
|
|
* If writers are committing on the reader page, knowing all
|
|
* committed content has been read, the ring buffer is empty.
|
|
*/
|
|
if (commit == reader)
|
|
return true;
|
|
|
|
/*
|
|
* If writers are committing on a page other than reader page
|
|
* and head page, there should always be content to read.
|
|
*/
|
|
if (commit != head)
|
|
return false;
|
|
|
|
/*
|
|
* Writers are committing on the head page, we just need
|
|
* to care about there're committed data, and the reader will
|
|
* swap reader page with head page when it is to read data.
|
|
*/
|
|
return rb_page_commit(commit) == 0;
|
|
}
|
|
|
|
/**
|
|
* ring_buffer_record_disable - stop all writes into the buffer
|
|
* @buffer: The ring buffer to stop writes to.
|
|
*
|
|
* This prevents all writes to the buffer. Any attempt to write
|
|
* to the buffer after this will fail and return NULL.
|
|
*
|
|
* The caller should call synchronize_rcu() after this.
|
|
*/
|
|
void ring_buffer_record_disable(struct trace_buffer *buffer)
|
|
{
|
|
atomic_inc(&buffer->record_disabled);
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_record_disable);
|
|
|
|
/**
|
|
* ring_buffer_record_enable - enable writes to the buffer
|
|
* @buffer: The ring buffer to enable writes
|
|
*
|
|
* Note, multiple disables will need the same number of enables
|
|
* to truly enable the writing (much like preempt_disable).
|
|
*/
|
|
void ring_buffer_record_enable(struct trace_buffer *buffer)
|
|
{
|
|
atomic_dec(&buffer->record_disabled);
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_record_enable);
|
|
|
|
/**
|
|
* ring_buffer_record_off - stop all writes into the buffer
|
|
* @buffer: The ring buffer to stop writes to.
|
|
*
|
|
* This prevents all writes to the buffer. Any attempt to write
|
|
* to the buffer after this will fail and return NULL.
|
|
*
|
|
* This is different than ring_buffer_record_disable() as
|
|
* it works like an on/off switch, where as the disable() version
|
|
* must be paired with a enable().
|
|
*/
|
|
void ring_buffer_record_off(struct trace_buffer *buffer)
|
|
{
|
|
unsigned int rd;
|
|
unsigned int new_rd;
|
|
|
|
rd = atomic_read(&buffer->record_disabled);
|
|
do {
|
|
new_rd = rd | RB_BUFFER_OFF;
|
|
} while (!atomic_try_cmpxchg(&buffer->record_disabled, &rd, new_rd));
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_record_off);
|
|
|
|
/**
|
|
* ring_buffer_record_on - restart writes into the buffer
|
|
* @buffer: The ring buffer to start writes to.
|
|
*
|
|
* This enables all writes to the buffer that was disabled by
|
|
* ring_buffer_record_off().
|
|
*
|
|
* This is different than ring_buffer_record_enable() as
|
|
* it works like an on/off switch, where as the enable() version
|
|
* must be paired with a disable().
|
|
*/
|
|
void ring_buffer_record_on(struct trace_buffer *buffer)
|
|
{
|
|
unsigned int rd;
|
|
unsigned int new_rd;
|
|
|
|
rd = atomic_read(&buffer->record_disabled);
|
|
do {
|
|
new_rd = rd & ~RB_BUFFER_OFF;
|
|
} while (!atomic_try_cmpxchg(&buffer->record_disabled, &rd, new_rd));
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_record_on);
|
|
|
|
/**
|
|
* ring_buffer_record_is_on - return true if the ring buffer can write
|
|
* @buffer: The ring buffer to see if write is enabled
|
|
*
|
|
* Returns true if the ring buffer is in a state that it accepts writes.
|
|
*/
|
|
bool ring_buffer_record_is_on(struct trace_buffer *buffer)
|
|
{
|
|
return !atomic_read(&buffer->record_disabled);
|
|
}
|
|
|
|
/**
|
|
* ring_buffer_record_is_set_on - return true if the ring buffer is set writable
|
|
* @buffer: The ring buffer to see if write is set enabled
|
|
*
|
|
* Returns true if the ring buffer is set writable by ring_buffer_record_on().
|
|
* Note that this does NOT mean it is in a writable state.
|
|
*
|
|
* It may return true when the ring buffer has been disabled by
|
|
* ring_buffer_record_disable(), as that is a temporary disabling of
|
|
* the ring buffer.
|
|
*/
|
|
bool ring_buffer_record_is_set_on(struct trace_buffer *buffer)
|
|
{
|
|
return !(atomic_read(&buffer->record_disabled) & RB_BUFFER_OFF);
|
|
}
|
|
|
|
/**
|
|
* ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
|
|
* @buffer: The ring buffer to stop writes to.
|
|
* @cpu: The CPU buffer to stop
|
|
*
|
|
* This prevents all writes to the buffer. Any attempt to write
|
|
* to the buffer after this will fail and return NULL.
|
|
*
|
|
* The caller should call synchronize_rcu() after this.
|
|
*/
|
|
void ring_buffer_record_disable_cpu(struct trace_buffer *buffer, int cpu)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
return;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
atomic_inc(&cpu_buffer->record_disabled);
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu);
|
|
|
|
/**
|
|
* ring_buffer_record_enable_cpu - enable writes to the buffer
|
|
* @buffer: The ring buffer to enable writes
|
|
* @cpu: The CPU to enable.
|
|
*
|
|
* Note, multiple disables will need the same number of enables
|
|
* to truly enable the writing (much like preempt_disable).
|
|
*/
|
|
void ring_buffer_record_enable_cpu(struct trace_buffer *buffer, int cpu)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
return;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
atomic_dec(&cpu_buffer->record_disabled);
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu);
|
|
|
|
/*
|
|
* The total entries in the ring buffer is the running counter
|
|
* of entries entered into the ring buffer, minus the sum of
|
|
* the entries read from the ring buffer and the number of
|
|
* entries that were overwritten.
|
|
*/
|
|
static inline unsigned long
|
|
rb_num_of_entries(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
return local_read(&cpu_buffer->entries) -
|
|
(local_read(&cpu_buffer->overrun) + cpu_buffer->read);
|
|
}
|
|
|
|
/**
|
|
* ring_buffer_oldest_event_ts - get the oldest event timestamp from the buffer
|
|
* @buffer: The ring buffer
|
|
* @cpu: The per CPU buffer to read from.
|
|
*/
|
|
u64 ring_buffer_oldest_event_ts(struct trace_buffer *buffer, int cpu)
|
|
{
|
|
unsigned long flags;
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
struct buffer_page *bpage;
|
|
u64 ret = 0;
|
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
return 0;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
|
|
/*
|
|
* if the tail is on reader_page, oldest time stamp is on the reader
|
|
* page
|
|
*/
|
|
if (cpu_buffer->tail_page == cpu_buffer->reader_page)
|
|
bpage = cpu_buffer->reader_page;
|
|
else
|
|
bpage = rb_set_head_page(cpu_buffer);
|
|
if (bpage)
|
|
ret = bpage->page->time_stamp;
|
|
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
|
|
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_oldest_event_ts);
|
|
|
|
/**
|
|
* ring_buffer_bytes_cpu - get the number of bytes unconsumed in a cpu buffer
|
|
* @buffer: The ring buffer
|
|
* @cpu: The per CPU buffer to read from.
|
|
*/
|
|
unsigned long ring_buffer_bytes_cpu(struct trace_buffer *buffer, int cpu)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
unsigned long ret;
|
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
return 0;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
ret = local_read(&cpu_buffer->entries_bytes) - cpu_buffer->read_bytes;
|
|
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_bytes_cpu);
|
|
|
|
/**
|
|
* ring_buffer_entries_cpu - get the number of entries in a cpu buffer
|
|
* @buffer: The ring buffer
|
|
* @cpu: The per CPU buffer to get the entries from.
|
|
*/
|
|
unsigned long ring_buffer_entries_cpu(struct trace_buffer *buffer, int cpu)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
return 0;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
|
|
return rb_num_of_entries(cpu_buffer);
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu);
|
|
|
|
/**
|
|
* ring_buffer_overrun_cpu - get the number of overruns caused by the ring
|
|
* buffer wrapping around (only if RB_FL_OVERWRITE is on).
|
|
* @buffer: The ring buffer
|
|
* @cpu: The per CPU buffer to get the number of overruns from
|
|
*/
|
|
unsigned long ring_buffer_overrun_cpu(struct trace_buffer *buffer, int cpu)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
unsigned long ret;
|
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
return 0;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
ret = local_read(&cpu_buffer->overrun);
|
|
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu);
|
|
|
|
/**
|
|
* ring_buffer_commit_overrun_cpu - get the number of overruns caused by
|
|
* commits failing due to the buffer wrapping around while there are uncommitted
|
|
* events, such as during an interrupt storm.
|
|
* @buffer: The ring buffer
|
|
* @cpu: The per CPU buffer to get the number of overruns from
|
|
*/
|
|
unsigned long
|
|
ring_buffer_commit_overrun_cpu(struct trace_buffer *buffer, int cpu)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
unsigned long ret;
|
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
return 0;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
ret = local_read(&cpu_buffer->commit_overrun);
|
|
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_commit_overrun_cpu);
|
|
|
|
/**
|
|
* ring_buffer_dropped_events_cpu - get the number of dropped events caused by
|
|
* the ring buffer filling up (only if RB_FL_OVERWRITE is off).
|
|
* @buffer: The ring buffer
|
|
* @cpu: The per CPU buffer to get the number of overruns from
|
|
*/
|
|
unsigned long
|
|
ring_buffer_dropped_events_cpu(struct trace_buffer *buffer, int cpu)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
unsigned long ret;
|
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
return 0;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
ret = local_read(&cpu_buffer->dropped_events);
|
|
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_dropped_events_cpu);
|
|
|
|
/**
|
|
* ring_buffer_read_events_cpu - get the number of events successfully read
|
|
* @buffer: The ring buffer
|
|
* @cpu: The per CPU buffer to get the number of events read
|
|
*/
|
|
unsigned long
|
|
ring_buffer_read_events_cpu(struct trace_buffer *buffer, int cpu)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
return 0;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
return cpu_buffer->read;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_read_events_cpu);
|
|
|
|
/**
|
|
* ring_buffer_entries - get the number of entries in a buffer
|
|
* @buffer: The ring buffer
|
|
*
|
|
* Returns the total number of entries in the ring buffer
|
|
* (all CPU entries)
|
|
*/
|
|
unsigned long ring_buffer_entries(struct trace_buffer *buffer)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
unsigned long entries = 0;
|
|
int cpu;
|
|
|
|
/* if you care about this being correct, lock the buffer */
|
|
for_each_buffer_cpu(buffer, cpu) {
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
entries += rb_num_of_entries(cpu_buffer);
|
|
}
|
|
|
|
return entries;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_entries);
|
|
|
|
/**
|
|
* ring_buffer_overruns - get the number of overruns in buffer
|
|
* @buffer: The ring buffer
|
|
*
|
|
* Returns the total number of overruns in the ring buffer
|
|
* (all CPU entries)
|
|
*/
|
|
unsigned long ring_buffer_overruns(struct trace_buffer *buffer)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
unsigned long overruns = 0;
|
|
int cpu;
|
|
|
|
/* if you care about this being correct, lock the buffer */
|
|
for_each_buffer_cpu(buffer, cpu) {
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
overruns += local_read(&cpu_buffer->overrun);
|
|
}
|
|
|
|
return overruns;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_overruns);
|
|
|
|
static void rb_iter_reset(struct ring_buffer_iter *iter)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
|
|
|
|
/* Iterator usage is expected to have record disabled */
|
|
iter->head_page = cpu_buffer->reader_page;
|
|
iter->head = cpu_buffer->reader_page->read;
|
|
iter->next_event = iter->head;
|
|
|
|
iter->cache_reader_page = iter->head_page;
|
|
iter->cache_read = cpu_buffer->read;
|
|
iter->cache_pages_removed = cpu_buffer->pages_removed;
|
|
|
|
if (iter->head) {
|
|
iter->read_stamp = cpu_buffer->read_stamp;
|
|
iter->page_stamp = cpu_buffer->reader_page->page->time_stamp;
|
|
} else {
|
|
iter->read_stamp = iter->head_page->page->time_stamp;
|
|
iter->page_stamp = iter->read_stamp;
|
|
}
|
|
}
|
|
|
|
/**
|
|
* ring_buffer_iter_reset - reset an iterator
|
|
* @iter: The iterator to reset
|
|
*
|
|
* Resets the iterator, so that it will start from the beginning
|
|
* again.
|
|
*/
|
|
void ring_buffer_iter_reset(struct ring_buffer_iter *iter)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
unsigned long flags;
|
|
|
|
if (!iter)
|
|
return;
|
|
|
|
cpu_buffer = iter->cpu_buffer;
|
|
|
|
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
|
|
rb_iter_reset(iter);
|
|
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_iter_reset);
|
|
|
|
/**
|
|
* ring_buffer_iter_empty - check if an iterator has no more to read
|
|
* @iter: The iterator to check
|
|
*/
|
|
int ring_buffer_iter_empty(struct ring_buffer_iter *iter)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
struct buffer_page *reader;
|
|
struct buffer_page *head_page;
|
|
struct buffer_page *commit_page;
|
|
struct buffer_page *curr_commit_page;
|
|
unsigned commit;
|
|
u64 curr_commit_ts;
|
|
u64 commit_ts;
|
|
|
|
cpu_buffer = iter->cpu_buffer;
|
|
reader = cpu_buffer->reader_page;
|
|
head_page = cpu_buffer->head_page;
|
|
commit_page = READ_ONCE(cpu_buffer->commit_page);
|
|
commit_ts = commit_page->page->time_stamp;
|
|
|
|
/*
|
|
* When the writer goes across pages, it issues a cmpxchg which
|
|
* is a mb(), which will synchronize with the rmb here.
|
|
* (see rb_tail_page_update())
|
|
*/
|
|
smp_rmb();
|
|
commit = rb_page_commit(commit_page);
|
|
/* We want to make sure that the commit page doesn't change */
|
|
smp_rmb();
|
|
|
|
/* Make sure commit page didn't change */
|
|
curr_commit_page = READ_ONCE(cpu_buffer->commit_page);
|
|
curr_commit_ts = READ_ONCE(curr_commit_page->page->time_stamp);
|
|
|
|
/* If the commit page changed, then there's more data */
|
|
if (curr_commit_page != commit_page ||
|
|
curr_commit_ts != commit_ts)
|
|
return 0;
|
|
|
|
/* Still racy, as it may return a false positive, but that's OK */
|
|
return ((iter->head_page == commit_page && iter->head >= commit) ||
|
|
(iter->head_page == reader && commit_page == head_page &&
|
|
head_page->read == commit &&
|
|
iter->head == rb_page_size(cpu_buffer->reader_page)));
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_iter_empty);
|
|
|
|
static void
|
|
rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer,
|
|
struct ring_buffer_event *event)
|
|
{
|
|
u64 delta;
|
|
|
|
switch (event->type_len) {
|
|
case RINGBUF_TYPE_PADDING:
|
|
return;
|
|
|
|
case RINGBUF_TYPE_TIME_EXTEND:
|
|
delta = rb_event_time_stamp(event);
|
|
cpu_buffer->read_stamp += delta;
|
|
return;
|
|
|
|
case RINGBUF_TYPE_TIME_STAMP:
|
|
delta = rb_event_time_stamp(event);
|
|
delta = rb_fix_abs_ts(delta, cpu_buffer->read_stamp);
|
|
cpu_buffer->read_stamp = delta;
|
|
return;
|
|
|
|
case RINGBUF_TYPE_DATA:
|
|
cpu_buffer->read_stamp += event->time_delta;
|
|
return;
|
|
|
|
default:
|
|
RB_WARN_ON(cpu_buffer, 1);
|
|
}
|
|
}
|
|
|
|
static void
|
|
rb_update_iter_read_stamp(struct ring_buffer_iter *iter,
|
|
struct ring_buffer_event *event)
|
|
{
|
|
u64 delta;
|
|
|
|
switch (event->type_len) {
|
|
case RINGBUF_TYPE_PADDING:
|
|
return;
|
|
|
|
case RINGBUF_TYPE_TIME_EXTEND:
|
|
delta = rb_event_time_stamp(event);
|
|
iter->read_stamp += delta;
|
|
return;
|
|
|
|
case RINGBUF_TYPE_TIME_STAMP:
|
|
delta = rb_event_time_stamp(event);
|
|
delta = rb_fix_abs_ts(delta, iter->read_stamp);
|
|
iter->read_stamp = delta;
|
|
return;
|
|
|
|
case RINGBUF_TYPE_DATA:
|
|
iter->read_stamp += event->time_delta;
|
|
return;
|
|
|
|
default:
|
|
RB_WARN_ON(iter->cpu_buffer, 1);
|
|
}
|
|
}
|
|
|
|
static struct buffer_page *
|
|
rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
struct buffer_page *reader = NULL;
|
|
unsigned long bsize = READ_ONCE(cpu_buffer->buffer->subbuf_size);
|
|
unsigned long overwrite;
|
|
unsigned long flags;
|
|
int nr_loops = 0;
|
|
bool ret;
|
|
|
|
local_irq_save(flags);
|
|
arch_spin_lock(&cpu_buffer->lock);
|
|
|
|
again:
|
|
/*
|
|
* This should normally only loop twice. But because the
|
|
* start of the reader inserts an empty page, it causes
|
|
* a case where we will loop three times. There should be no
|
|
* reason to loop four times (that I know of).
|
|
*/
|
|
if (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) {
|
|
reader = NULL;
|
|
goto out;
|
|
}
|
|
|
|
reader = cpu_buffer->reader_page;
|
|
|
|
/* If there's more to read, return this page */
|
|
if (cpu_buffer->reader_page->read < rb_page_size(reader))
|
|
goto out;
|
|
|
|
/* Never should we have an index greater than the size */
|
|
if (RB_WARN_ON(cpu_buffer,
|
|
cpu_buffer->reader_page->read > rb_page_size(reader)))
|
|
goto out;
|
|
|
|
/* check if we caught up to the tail */
|
|
reader = NULL;
|
|
if (cpu_buffer->commit_page == cpu_buffer->reader_page)
|
|
goto out;
|
|
|
|
/* Don't bother swapping if the ring buffer is empty */
|
|
if (rb_num_of_entries(cpu_buffer) == 0)
|
|
goto out;
|
|
|
|
/*
|
|
* Reset the reader page to size zero.
|
|
*/
|
|
local_set(&cpu_buffer->reader_page->write, 0);
|
|
local_set(&cpu_buffer->reader_page->entries, 0);
|
|
local_set(&cpu_buffer->reader_page->page->commit, 0);
|
|
cpu_buffer->reader_page->real_end = 0;
|
|
|
|
spin:
|
|
/*
|
|
* Splice the empty reader page into the list around the head.
|
|
*/
|
|
reader = rb_set_head_page(cpu_buffer);
|
|
if (!reader)
|
|
goto out;
|
|
cpu_buffer->reader_page->list.next = rb_list_head(reader->list.next);
|
|
cpu_buffer->reader_page->list.prev = reader->list.prev;
|
|
|
|
/*
|
|
* cpu_buffer->pages just needs to point to the buffer, it
|
|
* has no specific buffer page to point to. Lets move it out
|
|
* of our way so we don't accidentally swap it.
|
|
*/
|
|
cpu_buffer->pages = reader->list.prev;
|
|
|
|
/* The reader page will be pointing to the new head */
|
|
rb_set_list_to_head(&cpu_buffer->reader_page->list);
|
|
|
|
/*
|
|
* We want to make sure we read the overruns after we set up our
|
|
* pointers to the next object. The writer side does a
|
|
* cmpxchg to cross pages which acts as the mb on the writer
|
|
* side. Note, the reader will constantly fail the swap
|
|
* while the writer is updating the pointers, so this
|
|
* guarantees that the overwrite recorded here is the one we
|
|
* want to compare with the last_overrun.
|
|
*/
|
|
smp_mb();
|
|
overwrite = local_read(&(cpu_buffer->overrun));
|
|
|
|
/*
|
|
* Here's the tricky part.
|
|
*
|
|
* We need to move the pointer past the header page.
|
|
* But we can only do that if a writer is not currently
|
|
* moving it. The page before the header page has the
|
|
* flag bit '1' set if it is pointing to the page we want.
|
|
* but if the writer is in the process of moving it
|
|
* than it will be '2' or already moved '0'.
|
|
*/
|
|
|
|
ret = rb_head_page_replace(reader, cpu_buffer->reader_page);
|
|
|
|
/*
|
|
* If we did not convert it, then we must try again.
|
|
*/
|
|
if (!ret)
|
|
goto spin;
|
|
|
|
/*
|
|
* Yay! We succeeded in replacing the page.
|
|
*
|
|
* Now make the new head point back to the reader page.
|
|
*/
|
|
rb_list_head(reader->list.next)->prev = &cpu_buffer->reader_page->list;
|
|
rb_inc_page(&cpu_buffer->head_page);
|
|
|
|
local_inc(&cpu_buffer->pages_read);
|
|
|
|
/* Finally update the reader page to the new head */
|
|
cpu_buffer->reader_page = reader;
|
|
cpu_buffer->reader_page->read = 0;
|
|
|
|
if (overwrite != cpu_buffer->last_overrun) {
|
|
cpu_buffer->lost_events = overwrite - cpu_buffer->last_overrun;
|
|
cpu_buffer->last_overrun = overwrite;
|
|
}
|
|
|
|
goto again;
|
|
|
|
out:
|
|
/* Update the read_stamp on the first event */
|
|
if (reader && reader->read == 0)
|
|
cpu_buffer->read_stamp = reader->page->time_stamp;
|
|
|
|
arch_spin_unlock(&cpu_buffer->lock);
|
|
local_irq_restore(flags);
|
|
|
|
/*
|
|
* The writer has preempt disable, wait for it. But not forever
|
|
* Although, 1 second is pretty much "forever"
|
|
*/
|
|
#define USECS_WAIT 1000000
|
|
for (nr_loops = 0; nr_loops < USECS_WAIT; nr_loops++) {
|
|
/* If the write is past the end of page, a writer is still updating it */
|
|
if (likely(!reader || rb_page_write(reader) <= bsize))
|
|
break;
|
|
|
|
udelay(1);
|
|
|
|
/* Get the latest version of the reader write value */
|
|
smp_rmb();
|
|
}
|
|
|
|
/* The writer is not moving forward? Something is wrong */
|
|
if (RB_WARN_ON(cpu_buffer, nr_loops == USECS_WAIT))
|
|
reader = NULL;
|
|
|
|
/*
|
|
* Make sure we see any padding after the write update
|
|
* (see rb_reset_tail()).
|
|
*
|
|
* In addition, a writer may be writing on the reader page
|
|
* if the page has not been fully filled, so the read barrier
|
|
* is also needed to make sure we see the content of what is
|
|
* committed by the writer (see rb_set_commit_to_write()).
|
|
*/
|
|
smp_rmb();
|
|
|
|
|
|
return reader;
|
|
}
|
|
|
|
static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
struct ring_buffer_event *event;
|
|
struct buffer_page *reader;
|
|
unsigned length;
|
|
|
|
reader = rb_get_reader_page(cpu_buffer);
|
|
|
|
/* This function should not be called when buffer is empty */
|
|
if (RB_WARN_ON(cpu_buffer, !reader))
|
|
return;
|
|
|
|
event = rb_reader_event(cpu_buffer);
|
|
|
|
if (event->type_len <= RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
|
|
cpu_buffer->read++;
|
|
|
|
rb_update_read_stamp(cpu_buffer, event);
|
|
|
|
length = rb_event_length(event);
|
|
cpu_buffer->reader_page->read += length;
|
|
cpu_buffer->read_bytes += length;
|
|
}
|
|
|
|
static void rb_advance_iter(struct ring_buffer_iter *iter)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
|
|
cpu_buffer = iter->cpu_buffer;
|
|
|
|
/* If head == next_event then we need to jump to the next event */
|
|
if (iter->head == iter->next_event) {
|
|
/* If the event gets overwritten again, there's nothing to do */
|
|
if (rb_iter_head_event(iter) == NULL)
|
|
return;
|
|
}
|
|
|
|
iter->head = iter->next_event;
|
|
|
|
/*
|
|
* Check if we are at the end of the buffer.
|
|
*/
|
|
if (iter->next_event >= rb_page_size(iter->head_page)) {
|
|
/* discarded commits can make the page empty */
|
|
if (iter->head_page == cpu_buffer->commit_page)
|
|
return;
|
|
rb_inc_iter(iter);
|
|
return;
|
|
}
|
|
|
|
rb_update_iter_read_stamp(iter, iter->event);
|
|
}
|
|
|
|
static int rb_lost_events(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
return cpu_buffer->lost_events;
|
|
}
|
|
|
|
static struct ring_buffer_event *
|
|
rb_buffer_peek(struct ring_buffer_per_cpu *cpu_buffer, u64 *ts,
|
|
unsigned long *lost_events)
|
|
{
|
|
struct ring_buffer_event *event;
|
|
struct buffer_page *reader;
|
|
int nr_loops = 0;
|
|
|
|
if (ts)
|
|
*ts = 0;
|
|
again:
|
|
/*
|
|
* We repeat when a time extend is encountered.
|
|
* Since the time extend is always attached to a data event,
|
|
* we should never loop more than once.
|
|
* (We never hit the following condition more than twice).
|
|
*/
|
|
if (RB_WARN_ON(cpu_buffer, ++nr_loops > 2))
|
|
return NULL;
|
|
|
|
reader = rb_get_reader_page(cpu_buffer);
|
|
if (!reader)
|
|
return NULL;
|
|
|
|
event = rb_reader_event(cpu_buffer);
|
|
|
|
switch (event->type_len) {
|
|
case RINGBUF_TYPE_PADDING:
|
|
if (rb_null_event(event))
|
|
RB_WARN_ON(cpu_buffer, 1);
|
|
/*
|
|
* Because the writer could be discarding every
|
|
* event it creates (which would probably be bad)
|
|
* if we were to go back to "again" then we may never
|
|
* catch up, and will trigger the warn on, or lock
|
|
* the box. Return the padding, and we will release
|
|
* the current locks, and try again.
|
|
*/
|
|
return event;
|
|
|
|
case RINGBUF_TYPE_TIME_EXTEND:
|
|
/* Internal data, OK to advance */
|
|
rb_advance_reader(cpu_buffer);
|
|
goto again;
|
|
|
|
case RINGBUF_TYPE_TIME_STAMP:
|
|
if (ts) {
|
|
*ts = rb_event_time_stamp(event);
|
|
*ts = rb_fix_abs_ts(*ts, reader->page->time_stamp);
|
|
ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
|
|
cpu_buffer->cpu, ts);
|
|
}
|
|
/* Internal data, OK to advance */
|
|
rb_advance_reader(cpu_buffer);
|
|
goto again;
|
|
|
|
case RINGBUF_TYPE_DATA:
|
|
if (ts && !(*ts)) {
|
|
*ts = cpu_buffer->read_stamp + event->time_delta;
|
|
ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
|
|
cpu_buffer->cpu, ts);
|
|
}
|
|
if (lost_events)
|
|
*lost_events = rb_lost_events(cpu_buffer);
|
|
return event;
|
|
|
|
default:
|
|
RB_WARN_ON(cpu_buffer, 1);
|
|
}
|
|
|
|
return NULL;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_peek);
|
|
|
|
static struct ring_buffer_event *
|
|
rb_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
|
|
{
|
|
struct trace_buffer *buffer;
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
struct ring_buffer_event *event;
|
|
int nr_loops = 0;
|
|
|
|
if (ts)
|
|
*ts = 0;
|
|
|
|
cpu_buffer = iter->cpu_buffer;
|
|
buffer = cpu_buffer->buffer;
|
|
|
|
/*
|
|
* Check if someone performed a consuming read to the buffer
|
|
* or removed some pages from the buffer. In these cases,
|
|
* iterator was invalidated and we need to reset it.
|
|
*/
|
|
if (unlikely(iter->cache_read != cpu_buffer->read ||
|
|
iter->cache_reader_page != cpu_buffer->reader_page ||
|
|
iter->cache_pages_removed != cpu_buffer->pages_removed))
|
|
rb_iter_reset(iter);
|
|
|
|
again:
|
|
if (ring_buffer_iter_empty(iter))
|
|
return NULL;
|
|
|
|
/*
|
|
* As the writer can mess with what the iterator is trying
|
|
* to read, just give up if we fail to get an event after
|
|
* three tries. The iterator is not as reliable when reading
|
|
* the ring buffer with an active write as the consumer is.
|
|
* Do not warn if the three failures is reached.
|
|
*/
|
|
if (++nr_loops > 3)
|
|
return NULL;
|
|
|
|
if (rb_per_cpu_empty(cpu_buffer))
|
|
return NULL;
|
|
|
|
if (iter->head >= rb_page_size(iter->head_page)) {
|
|
rb_inc_iter(iter);
|
|
goto again;
|
|
}
|
|
|
|
event = rb_iter_head_event(iter);
|
|
if (!event)
|
|
goto again;
|
|
|
|
switch (event->type_len) {
|
|
case RINGBUF_TYPE_PADDING:
|
|
if (rb_null_event(event)) {
|
|
rb_inc_iter(iter);
|
|
goto again;
|
|
}
|
|
rb_advance_iter(iter);
|
|
return event;
|
|
|
|
case RINGBUF_TYPE_TIME_EXTEND:
|
|
/* Internal data, OK to advance */
|
|
rb_advance_iter(iter);
|
|
goto again;
|
|
|
|
case RINGBUF_TYPE_TIME_STAMP:
|
|
if (ts) {
|
|
*ts = rb_event_time_stamp(event);
|
|
*ts = rb_fix_abs_ts(*ts, iter->head_page->page->time_stamp);
|
|
ring_buffer_normalize_time_stamp(cpu_buffer->buffer,
|
|
cpu_buffer->cpu, ts);
|
|
}
|
|
/* Internal data, OK to advance */
|
|
rb_advance_iter(iter);
|
|
goto again;
|
|
|
|
case RINGBUF_TYPE_DATA:
|
|
if (ts && !(*ts)) {
|
|
*ts = iter->read_stamp + event->time_delta;
|
|
ring_buffer_normalize_time_stamp(buffer,
|
|
cpu_buffer->cpu, ts);
|
|
}
|
|
return event;
|
|
|
|
default:
|
|
RB_WARN_ON(cpu_buffer, 1);
|
|
}
|
|
|
|
return NULL;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_iter_peek);
|
|
|
|
static inline bool rb_reader_lock(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
if (likely(!in_nmi())) {
|
|
raw_spin_lock(&cpu_buffer->reader_lock);
|
|
return true;
|
|
}
|
|
|
|
/*
|
|
* If an NMI die dumps out the content of the ring buffer
|
|
* trylock must be used to prevent a deadlock if the NMI
|
|
* preempted a task that holds the ring buffer locks. If
|
|
* we get the lock then all is fine, if not, then continue
|
|
* to do the read, but this can corrupt the ring buffer,
|
|
* so it must be permanently disabled from future writes.
|
|
* Reading from NMI is a oneshot deal.
|
|
*/
|
|
if (raw_spin_trylock(&cpu_buffer->reader_lock))
|
|
return true;
|
|
|
|
/* Continue without locking, but disable the ring buffer */
|
|
atomic_inc(&cpu_buffer->record_disabled);
|
|
return false;
|
|
}
|
|
|
|
static inline void
|
|
rb_reader_unlock(struct ring_buffer_per_cpu *cpu_buffer, bool locked)
|
|
{
|
|
if (likely(locked))
|
|
raw_spin_unlock(&cpu_buffer->reader_lock);
|
|
}
|
|
|
|
/**
|
|
* ring_buffer_peek - peek at the next event to be read
|
|
* @buffer: The ring buffer to read
|
|
* @cpu: The cpu to peak at
|
|
* @ts: The timestamp counter of this event.
|
|
* @lost_events: a variable to store if events were lost (may be NULL)
|
|
*
|
|
* This will return the event that will be read next, but does
|
|
* not consume the data.
|
|
*/
|
|
struct ring_buffer_event *
|
|
ring_buffer_peek(struct trace_buffer *buffer, int cpu, u64 *ts,
|
|
unsigned long *lost_events)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
|
|
struct ring_buffer_event *event;
|
|
unsigned long flags;
|
|
bool dolock;
|
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
return NULL;
|
|
|
|
again:
|
|
local_irq_save(flags);
|
|
dolock = rb_reader_lock(cpu_buffer);
|
|
event = rb_buffer_peek(cpu_buffer, ts, lost_events);
|
|
if (event && event->type_len == RINGBUF_TYPE_PADDING)
|
|
rb_advance_reader(cpu_buffer);
|
|
rb_reader_unlock(cpu_buffer, dolock);
|
|
local_irq_restore(flags);
|
|
|
|
if (event && event->type_len == RINGBUF_TYPE_PADDING)
|
|
goto again;
|
|
|
|
return event;
|
|
}
|
|
|
|
/** ring_buffer_iter_dropped - report if there are dropped events
|
|
* @iter: The ring buffer iterator
|
|
*
|
|
* Returns true if there was dropped events since the last peek.
|
|
*/
|
|
bool ring_buffer_iter_dropped(struct ring_buffer_iter *iter)
|
|
{
|
|
bool ret = iter->missed_events != 0;
|
|
|
|
iter->missed_events = 0;
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_iter_dropped);
|
|
|
|
/**
|
|
* ring_buffer_iter_peek - peek at the next event to be read
|
|
* @iter: The ring buffer iterator
|
|
* @ts: The timestamp counter of this event.
|
|
*
|
|
* This will return the event that will be read next, but does
|
|
* not increment the iterator.
|
|
*/
|
|
struct ring_buffer_event *
|
|
ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
|
|
struct ring_buffer_event *event;
|
|
unsigned long flags;
|
|
|
|
again:
|
|
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
|
|
event = rb_iter_peek(iter, ts);
|
|
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
|
|
|
|
if (event && event->type_len == RINGBUF_TYPE_PADDING)
|
|
goto again;
|
|
|
|
return event;
|
|
}
|
|
|
|
/**
|
|
* ring_buffer_consume - return an event and consume it
|
|
* @buffer: The ring buffer to get the next event from
|
|
* @cpu: the cpu to read the buffer from
|
|
* @ts: a variable to store the timestamp (may be NULL)
|
|
* @lost_events: a variable to store if events were lost (may be NULL)
|
|
*
|
|
* Returns the next event in the ring buffer, and that event is consumed.
|
|
* Meaning, that sequential reads will keep returning a different event,
|
|
* and eventually empty the ring buffer if the producer is slower.
|
|
*/
|
|
struct ring_buffer_event *
|
|
ring_buffer_consume(struct trace_buffer *buffer, int cpu, u64 *ts,
|
|
unsigned long *lost_events)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
struct ring_buffer_event *event = NULL;
|
|
unsigned long flags;
|
|
bool dolock;
|
|
|
|
again:
|
|
/* might be called in atomic */
|
|
preempt_disable();
|
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
goto out;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
local_irq_save(flags);
|
|
dolock = rb_reader_lock(cpu_buffer);
|
|
|
|
event = rb_buffer_peek(cpu_buffer, ts, lost_events);
|
|
if (event) {
|
|
cpu_buffer->lost_events = 0;
|
|
rb_advance_reader(cpu_buffer);
|
|
}
|
|
|
|
rb_reader_unlock(cpu_buffer, dolock);
|
|
local_irq_restore(flags);
|
|
|
|
out:
|
|
preempt_enable();
|
|
|
|
if (event && event->type_len == RINGBUF_TYPE_PADDING)
|
|
goto again;
|
|
|
|
return event;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_consume);
|
|
|
|
/**
|
|
* ring_buffer_read_prepare - Prepare for a non consuming read of the buffer
|
|
* @buffer: The ring buffer to read from
|
|
* @cpu: The cpu buffer to iterate over
|
|
* @flags: gfp flags to use for memory allocation
|
|
*
|
|
* This performs the initial preparations necessary to iterate
|
|
* through the buffer. Memory is allocated, buffer recording
|
|
* is disabled, and the iterator pointer is returned to the caller.
|
|
*
|
|
* Disabling buffer recording prevents the reading from being
|
|
* corrupted. This is not a consuming read, so a producer is not
|
|
* expected.
|
|
*
|
|
* After a sequence of ring_buffer_read_prepare calls, the user is
|
|
* expected to make at least one call to ring_buffer_read_prepare_sync.
|
|
* Afterwards, ring_buffer_read_start is invoked to get things going
|
|
* for real.
|
|
*
|
|
* This overall must be paired with ring_buffer_read_finish.
|
|
*/
|
|
struct ring_buffer_iter *
|
|
ring_buffer_read_prepare(struct trace_buffer *buffer, int cpu, gfp_t flags)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
struct ring_buffer_iter *iter;
|
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
return NULL;
|
|
|
|
iter = kzalloc(sizeof(*iter), flags);
|
|
if (!iter)
|
|
return NULL;
|
|
|
|
/* Holds the entire event: data and meta data */
|
|
iter->event_size = buffer->subbuf_size;
|
|
iter->event = kmalloc(iter->event_size, flags);
|
|
if (!iter->event) {
|
|
kfree(iter);
|
|
return NULL;
|
|
}
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
|
|
iter->cpu_buffer = cpu_buffer;
|
|
|
|
atomic_inc(&cpu_buffer->resize_disabled);
|
|
|
|
return iter;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_read_prepare);
|
|
|
|
/**
|
|
* ring_buffer_read_prepare_sync - Synchronize a set of prepare calls
|
|
*
|
|
* All previously invoked ring_buffer_read_prepare calls to prepare
|
|
* iterators will be synchronized. Afterwards, read_buffer_read_start
|
|
* calls on those iterators are allowed.
|
|
*/
|
|
void
|
|
ring_buffer_read_prepare_sync(void)
|
|
{
|
|
synchronize_rcu();
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_read_prepare_sync);
|
|
|
|
/**
|
|
* ring_buffer_read_start - start a non consuming read of the buffer
|
|
* @iter: The iterator returned by ring_buffer_read_prepare
|
|
*
|
|
* This finalizes the startup of an iteration through the buffer.
|
|
* The iterator comes from a call to ring_buffer_read_prepare and
|
|
* an intervening ring_buffer_read_prepare_sync must have been
|
|
* performed.
|
|
*
|
|
* Must be paired with ring_buffer_read_finish.
|
|
*/
|
|
void
|
|
ring_buffer_read_start(struct ring_buffer_iter *iter)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
unsigned long flags;
|
|
|
|
if (!iter)
|
|
return;
|
|
|
|
cpu_buffer = iter->cpu_buffer;
|
|
|
|
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
|
|
arch_spin_lock(&cpu_buffer->lock);
|
|
rb_iter_reset(iter);
|
|
arch_spin_unlock(&cpu_buffer->lock);
|
|
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_read_start);
|
|
|
|
/**
|
|
* ring_buffer_read_finish - finish reading the iterator of the buffer
|
|
* @iter: The iterator retrieved by ring_buffer_start
|
|
*
|
|
* This re-enables the recording to the buffer, and frees the
|
|
* iterator.
|
|
*/
|
|
void
|
|
ring_buffer_read_finish(struct ring_buffer_iter *iter)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
|
|
unsigned long flags;
|
|
|
|
/*
|
|
* Ring buffer is disabled from recording, here's a good place
|
|
* to check the integrity of the ring buffer.
|
|
* Must prevent readers from trying to read, as the check
|
|
* clears the HEAD page and readers require it.
|
|
*/
|
|
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
|
|
rb_check_pages(cpu_buffer);
|
|
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
|
|
|
|
atomic_dec(&cpu_buffer->resize_disabled);
|
|
kfree(iter->event);
|
|
kfree(iter);
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_read_finish);
|
|
|
|
/**
|
|
* ring_buffer_iter_advance - advance the iterator to the next location
|
|
* @iter: The ring buffer iterator
|
|
*
|
|
* Move the location of the iterator such that the next read will
|
|
* be the next location of the iterator.
|
|
*/
|
|
void ring_buffer_iter_advance(struct ring_buffer_iter *iter)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
|
|
unsigned long flags;
|
|
|
|
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
|
|
|
|
rb_advance_iter(iter);
|
|
|
|
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_iter_advance);
|
|
|
|
/**
|
|
* ring_buffer_size - return the size of the ring buffer (in bytes)
|
|
* @buffer: The ring buffer.
|
|
* @cpu: The CPU to get ring buffer size from.
|
|
*/
|
|
unsigned long ring_buffer_size(struct trace_buffer *buffer, int cpu)
|
|
{
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
return 0;
|
|
|
|
return buffer->subbuf_size * buffer->buffers[cpu]->nr_pages;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_size);
|
|
|
|
/**
|
|
* ring_buffer_max_event_size - return the max data size of an event
|
|
* @buffer: The ring buffer.
|
|
*
|
|
* Returns the maximum size an event can be.
|
|
*/
|
|
unsigned long ring_buffer_max_event_size(struct trace_buffer *buffer)
|
|
{
|
|
/* If abs timestamp is requested, events have a timestamp too */
|
|
if (ring_buffer_time_stamp_abs(buffer))
|
|
return buffer->max_data_size - RB_LEN_TIME_EXTEND;
|
|
return buffer->max_data_size;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_max_event_size);
|
|
|
|
static void rb_clear_buffer_page(struct buffer_page *page)
|
|
{
|
|
local_set(&page->write, 0);
|
|
local_set(&page->entries, 0);
|
|
rb_init_page(page->page);
|
|
page->read = 0;
|
|
}
|
|
|
|
static void rb_update_meta_page(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
struct trace_buffer_meta *meta = cpu_buffer->meta_page;
|
|
|
|
meta->reader.read = cpu_buffer->reader_page->read;
|
|
meta->reader.id = cpu_buffer->reader_page->id;
|
|
meta->reader.lost_events = cpu_buffer->lost_events;
|
|
|
|
meta->entries = local_read(&cpu_buffer->entries);
|
|
meta->overrun = local_read(&cpu_buffer->overrun);
|
|
meta->read = cpu_buffer->read;
|
|
|
|
/* Some archs do not have data cache coherency between kernel and user-space */
|
|
flush_dcache_folio(virt_to_folio(cpu_buffer->meta_page));
|
|
}
|
|
|
|
static void
|
|
rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
struct buffer_page *page;
|
|
|
|
rb_head_page_deactivate(cpu_buffer);
|
|
|
|
cpu_buffer->head_page
|
|
= list_entry(cpu_buffer->pages, struct buffer_page, list);
|
|
rb_clear_buffer_page(cpu_buffer->head_page);
|
|
list_for_each_entry(page, cpu_buffer->pages, list) {
|
|
rb_clear_buffer_page(page);
|
|
}
|
|
|
|
cpu_buffer->tail_page = cpu_buffer->head_page;
|
|
cpu_buffer->commit_page = cpu_buffer->head_page;
|
|
|
|
INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
|
|
INIT_LIST_HEAD(&cpu_buffer->new_pages);
|
|
rb_clear_buffer_page(cpu_buffer->reader_page);
|
|
|
|
local_set(&cpu_buffer->entries_bytes, 0);
|
|
local_set(&cpu_buffer->overrun, 0);
|
|
local_set(&cpu_buffer->commit_overrun, 0);
|
|
local_set(&cpu_buffer->dropped_events, 0);
|
|
local_set(&cpu_buffer->entries, 0);
|
|
local_set(&cpu_buffer->committing, 0);
|
|
local_set(&cpu_buffer->commits, 0);
|
|
local_set(&cpu_buffer->pages_touched, 0);
|
|
local_set(&cpu_buffer->pages_lost, 0);
|
|
local_set(&cpu_buffer->pages_read, 0);
|
|
cpu_buffer->last_pages_touch = 0;
|
|
cpu_buffer->shortest_full = 0;
|
|
cpu_buffer->read = 0;
|
|
cpu_buffer->read_bytes = 0;
|
|
|
|
rb_time_set(&cpu_buffer->write_stamp, 0);
|
|
rb_time_set(&cpu_buffer->before_stamp, 0);
|
|
|
|
memset(cpu_buffer->event_stamp, 0, sizeof(cpu_buffer->event_stamp));
|
|
|
|
cpu_buffer->lost_events = 0;
|
|
cpu_buffer->last_overrun = 0;
|
|
|
|
if (cpu_buffer->mapped)
|
|
rb_update_meta_page(cpu_buffer);
|
|
|
|
rb_head_page_activate(cpu_buffer);
|
|
cpu_buffer->pages_removed = 0;
|
|
}
|
|
|
|
/* Must have disabled the cpu buffer then done a synchronize_rcu */
|
|
static void reset_disabled_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
unsigned long flags;
|
|
|
|
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
|
|
|
|
if (RB_WARN_ON(cpu_buffer, local_read(&cpu_buffer->committing)))
|
|
goto out;
|
|
|
|
arch_spin_lock(&cpu_buffer->lock);
|
|
|
|
rb_reset_cpu(cpu_buffer);
|
|
|
|
arch_spin_unlock(&cpu_buffer->lock);
|
|
|
|
out:
|
|
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
|
|
}
|
|
|
|
/**
|
|
* ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
|
|
* @buffer: The ring buffer to reset a per cpu buffer of
|
|
* @cpu: The CPU buffer to be reset
|
|
*/
|
|
void ring_buffer_reset_cpu(struct trace_buffer *buffer, int cpu)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
|
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
return;
|
|
|
|
/* prevent another thread from changing buffer sizes */
|
|
mutex_lock(&buffer->mutex);
|
|
|
|
atomic_inc(&cpu_buffer->resize_disabled);
|
|
atomic_inc(&cpu_buffer->record_disabled);
|
|
|
|
/* Make sure all commits have finished */
|
|
synchronize_rcu();
|
|
|
|
reset_disabled_cpu_buffer(cpu_buffer);
|
|
|
|
atomic_dec(&cpu_buffer->record_disabled);
|
|
atomic_dec(&cpu_buffer->resize_disabled);
|
|
|
|
mutex_unlock(&buffer->mutex);
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu);
|
|
|
|
/* Flag to ensure proper resetting of atomic variables */
|
|
#define RESET_BIT (1 << 30)
|
|
|
|
/**
|
|
* ring_buffer_reset_online_cpus - reset a ring buffer per CPU buffer
|
|
* @buffer: The ring buffer to reset a per cpu buffer of
|
|
*/
|
|
void ring_buffer_reset_online_cpus(struct trace_buffer *buffer)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
int cpu;
|
|
|
|
/* prevent another thread from changing buffer sizes */
|
|
mutex_lock(&buffer->mutex);
|
|
|
|
for_each_online_buffer_cpu(buffer, cpu) {
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
|
|
atomic_add(RESET_BIT, &cpu_buffer->resize_disabled);
|
|
atomic_inc(&cpu_buffer->record_disabled);
|
|
}
|
|
|
|
/* Make sure all commits have finished */
|
|
synchronize_rcu();
|
|
|
|
for_each_buffer_cpu(buffer, cpu) {
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
|
|
/*
|
|
* If a CPU came online during the synchronize_rcu(), then
|
|
* ignore it.
|
|
*/
|
|
if (!(atomic_read(&cpu_buffer->resize_disabled) & RESET_BIT))
|
|
continue;
|
|
|
|
reset_disabled_cpu_buffer(cpu_buffer);
|
|
|
|
atomic_dec(&cpu_buffer->record_disabled);
|
|
atomic_sub(RESET_BIT, &cpu_buffer->resize_disabled);
|
|
}
|
|
|
|
mutex_unlock(&buffer->mutex);
|
|
}
|
|
|
|
/**
|
|
* ring_buffer_reset - reset a ring buffer
|
|
* @buffer: The ring buffer to reset all cpu buffers
|
|
*/
|
|
void ring_buffer_reset(struct trace_buffer *buffer)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
int cpu;
|
|
|
|
/* prevent another thread from changing buffer sizes */
|
|
mutex_lock(&buffer->mutex);
|
|
|
|
for_each_buffer_cpu(buffer, cpu) {
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
|
|
atomic_inc(&cpu_buffer->resize_disabled);
|
|
atomic_inc(&cpu_buffer->record_disabled);
|
|
}
|
|
|
|
/* Make sure all commits have finished */
|
|
synchronize_rcu();
|
|
|
|
for_each_buffer_cpu(buffer, cpu) {
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
|
|
reset_disabled_cpu_buffer(cpu_buffer);
|
|
|
|
atomic_dec(&cpu_buffer->record_disabled);
|
|
atomic_dec(&cpu_buffer->resize_disabled);
|
|
}
|
|
|
|
mutex_unlock(&buffer->mutex);
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_reset);
|
|
|
|
/**
|
|
* ring_buffer_empty - is the ring buffer empty?
|
|
* @buffer: The ring buffer to test
|
|
*/
|
|
bool ring_buffer_empty(struct trace_buffer *buffer)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
unsigned long flags;
|
|
bool dolock;
|
|
bool ret;
|
|
int cpu;
|
|
|
|
/* yes this is racy, but if you don't like the race, lock the buffer */
|
|
for_each_buffer_cpu(buffer, cpu) {
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
local_irq_save(flags);
|
|
dolock = rb_reader_lock(cpu_buffer);
|
|
ret = rb_per_cpu_empty(cpu_buffer);
|
|
rb_reader_unlock(cpu_buffer, dolock);
|
|
local_irq_restore(flags);
|
|
|
|
if (!ret)
|
|
return false;
|
|
}
|
|
|
|
return true;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_empty);
|
|
|
|
/**
|
|
* ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
|
|
* @buffer: The ring buffer
|
|
* @cpu: The CPU buffer to test
|
|
*/
|
|
bool ring_buffer_empty_cpu(struct trace_buffer *buffer, int cpu)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
unsigned long flags;
|
|
bool dolock;
|
|
bool ret;
|
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
return true;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
local_irq_save(flags);
|
|
dolock = rb_reader_lock(cpu_buffer);
|
|
ret = rb_per_cpu_empty(cpu_buffer);
|
|
rb_reader_unlock(cpu_buffer, dolock);
|
|
local_irq_restore(flags);
|
|
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu);
|
|
|
|
#ifdef CONFIG_RING_BUFFER_ALLOW_SWAP
|
|
/**
|
|
* ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
|
|
* @buffer_a: One buffer to swap with
|
|
* @buffer_b: The other buffer to swap with
|
|
* @cpu: the CPU of the buffers to swap
|
|
*
|
|
* This function is useful for tracers that want to take a "snapshot"
|
|
* of a CPU buffer and has another back up buffer lying around.
|
|
* it is expected that the tracer handles the cpu buffer not being
|
|
* used at the moment.
|
|
*/
|
|
int ring_buffer_swap_cpu(struct trace_buffer *buffer_a,
|
|
struct trace_buffer *buffer_b, int cpu)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer_a;
|
|
struct ring_buffer_per_cpu *cpu_buffer_b;
|
|
int ret = -EINVAL;
|
|
|
|
if (!cpumask_test_cpu(cpu, buffer_a->cpumask) ||
|
|
!cpumask_test_cpu(cpu, buffer_b->cpumask))
|
|
goto out;
|
|
|
|
cpu_buffer_a = buffer_a->buffers[cpu];
|
|
cpu_buffer_b = buffer_b->buffers[cpu];
|
|
|
|
/* It's up to the callers to not try to swap mapped buffers */
|
|
if (WARN_ON_ONCE(cpu_buffer_a->mapped || cpu_buffer_b->mapped)) {
|
|
ret = -EBUSY;
|
|
goto out;
|
|
}
|
|
|
|
/* At least make sure the two buffers are somewhat the same */
|
|
if (cpu_buffer_a->nr_pages != cpu_buffer_b->nr_pages)
|
|
goto out;
|
|
|
|
if (buffer_a->subbuf_order != buffer_b->subbuf_order)
|
|
goto out;
|
|
|
|
ret = -EAGAIN;
|
|
|
|
if (atomic_read(&buffer_a->record_disabled))
|
|
goto out;
|
|
|
|
if (atomic_read(&buffer_b->record_disabled))
|
|
goto out;
|
|
|
|
if (atomic_read(&cpu_buffer_a->record_disabled))
|
|
goto out;
|
|
|
|
if (atomic_read(&cpu_buffer_b->record_disabled))
|
|
goto out;
|
|
|
|
/*
|
|
* We can't do a synchronize_rcu here because this
|
|
* function can be called in atomic context.
|
|
* Normally this will be called from the same CPU as cpu.
|
|
* If not it's up to the caller to protect this.
|
|
*/
|
|
atomic_inc(&cpu_buffer_a->record_disabled);
|
|
atomic_inc(&cpu_buffer_b->record_disabled);
|
|
|
|
ret = -EBUSY;
|
|
if (local_read(&cpu_buffer_a->committing))
|
|
goto out_dec;
|
|
if (local_read(&cpu_buffer_b->committing))
|
|
goto out_dec;
|
|
|
|
/*
|
|
* When resize is in progress, we cannot swap it because
|
|
* it will mess the state of the cpu buffer.
|
|
*/
|
|
if (atomic_read(&buffer_a->resizing))
|
|
goto out_dec;
|
|
if (atomic_read(&buffer_b->resizing))
|
|
goto out_dec;
|
|
|
|
buffer_a->buffers[cpu] = cpu_buffer_b;
|
|
buffer_b->buffers[cpu] = cpu_buffer_a;
|
|
|
|
cpu_buffer_b->buffer = buffer_a;
|
|
cpu_buffer_a->buffer = buffer_b;
|
|
|
|
ret = 0;
|
|
|
|
out_dec:
|
|
atomic_dec(&cpu_buffer_a->record_disabled);
|
|
atomic_dec(&cpu_buffer_b->record_disabled);
|
|
out:
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu);
|
|
#endif /* CONFIG_RING_BUFFER_ALLOW_SWAP */
|
|
|
|
/**
|
|
* ring_buffer_alloc_read_page - allocate a page to read from buffer
|
|
* @buffer: the buffer to allocate for.
|
|
* @cpu: the cpu buffer to allocate.
|
|
*
|
|
* This function is used in conjunction with ring_buffer_read_page.
|
|
* When reading a full page from the ring buffer, these functions
|
|
* can be used to speed up the process. The calling function should
|
|
* allocate a few pages first with this function. Then when it
|
|
* needs to get pages from the ring buffer, it passes the result
|
|
* of this function into ring_buffer_read_page, which will swap
|
|
* the page that was allocated, with the read page of the buffer.
|
|
*
|
|
* Returns:
|
|
* The page allocated, or ERR_PTR
|
|
*/
|
|
struct buffer_data_read_page *
|
|
ring_buffer_alloc_read_page(struct trace_buffer *buffer, int cpu)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
struct buffer_data_read_page *bpage = NULL;
|
|
unsigned long flags;
|
|
struct page *page;
|
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
return ERR_PTR(-ENODEV);
|
|
|
|
bpage = kzalloc(sizeof(*bpage), GFP_KERNEL);
|
|
if (!bpage)
|
|
return ERR_PTR(-ENOMEM);
|
|
|
|
bpage->order = buffer->subbuf_order;
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
local_irq_save(flags);
|
|
arch_spin_lock(&cpu_buffer->lock);
|
|
|
|
if (cpu_buffer->free_page) {
|
|
bpage->data = cpu_buffer->free_page;
|
|
cpu_buffer->free_page = NULL;
|
|
}
|
|
|
|
arch_spin_unlock(&cpu_buffer->lock);
|
|
local_irq_restore(flags);
|
|
|
|
if (bpage->data)
|
|
goto out;
|
|
|
|
page = alloc_pages_node(cpu_to_node(cpu),
|
|
GFP_KERNEL | __GFP_NORETRY | __GFP_COMP | __GFP_ZERO,
|
|
cpu_buffer->buffer->subbuf_order);
|
|
if (!page) {
|
|
kfree(bpage);
|
|
return ERR_PTR(-ENOMEM);
|
|
}
|
|
|
|
bpage->data = page_address(page);
|
|
|
|
out:
|
|
rb_init_page(bpage->data);
|
|
|
|
return bpage;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page);
|
|
|
|
/**
|
|
* ring_buffer_free_read_page - free an allocated read page
|
|
* @buffer: the buffer the page was allocate for
|
|
* @cpu: the cpu buffer the page came from
|
|
* @data_page: the page to free
|
|
*
|
|
* Free a page allocated from ring_buffer_alloc_read_page.
|
|
*/
|
|
void ring_buffer_free_read_page(struct trace_buffer *buffer, int cpu,
|
|
struct buffer_data_read_page *data_page)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
struct buffer_data_page *bpage = data_page->data;
|
|
struct page *page = virt_to_page(bpage);
|
|
unsigned long flags;
|
|
|
|
if (!buffer || !buffer->buffers || !buffer->buffers[cpu])
|
|
return;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
|
|
/*
|
|
* If the page is still in use someplace else, or order of the page
|
|
* is different from the subbuffer order of the buffer -
|
|
* we can't reuse it
|
|
*/
|
|
if (page_ref_count(page) > 1 || data_page->order != buffer->subbuf_order)
|
|
goto out;
|
|
|
|
local_irq_save(flags);
|
|
arch_spin_lock(&cpu_buffer->lock);
|
|
|
|
if (!cpu_buffer->free_page) {
|
|
cpu_buffer->free_page = bpage;
|
|
bpage = NULL;
|
|
}
|
|
|
|
arch_spin_unlock(&cpu_buffer->lock);
|
|
local_irq_restore(flags);
|
|
|
|
out:
|
|
free_pages((unsigned long)bpage, data_page->order);
|
|
kfree(data_page);
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_free_read_page);
|
|
|
|
/**
|
|
* ring_buffer_read_page - extract a page from the ring buffer
|
|
* @buffer: buffer to extract from
|
|
* @data_page: the page to use allocated from ring_buffer_alloc_read_page
|
|
* @len: amount to extract
|
|
* @cpu: the cpu of the buffer to extract
|
|
* @full: should the extraction only happen when the page is full.
|
|
*
|
|
* This function will pull out a page from the ring buffer and consume it.
|
|
* @data_page must be the address of the variable that was returned
|
|
* from ring_buffer_alloc_read_page. This is because the page might be used
|
|
* to swap with a page in the ring buffer.
|
|
*
|
|
* for example:
|
|
* rpage = ring_buffer_alloc_read_page(buffer, cpu);
|
|
* if (IS_ERR(rpage))
|
|
* return PTR_ERR(rpage);
|
|
* ret = ring_buffer_read_page(buffer, rpage, len, cpu, 0);
|
|
* if (ret >= 0)
|
|
* process_page(ring_buffer_read_page_data(rpage), ret);
|
|
* ring_buffer_free_read_page(buffer, cpu, rpage);
|
|
*
|
|
* When @full is set, the function will not return true unless
|
|
* the writer is off the reader page.
|
|
*
|
|
* Note: it is up to the calling functions to handle sleeps and wakeups.
|
|
* The ring buffer can be used anywhere in the kernel and can not
|
|
* blindly call wake_up. The layer that uses the ring buffer must be
|
|
* responsible for that.
|
|
*
|
|
* Returns:
|
|
* >=0 if data has been transferred, returns the offset of consumed data.
|
|
* <0 if no data has been transferred.
|
|
*/
|
|
int ring_buffer_read_page(struct trace_buffer *buffer,
|
|
struct buffer_data_read_page *data_page,
|
|
size_t len, int cpu, int full)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
|
|
struct ring_buffer_event *event;
|
|
struct buffer_data_page *bpage;
|
|
struct buffer_page *reader;
|
|
unsigned long missed_events;
|
|
unsigned long flags;
|
|
unsigned int commit;
|
|
unsigned int read;
|
|
u64 save_timestamp;
|
|
int ret = -1;
|
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
goto out;
|
|
|
|
/*
|
|
* If len is not big enough to hold the page header, then
|
|
* we can not copy anything.
|
|
*/
|
|
if (len <= BUF_PAGE_HDR_SIZE)
|
|
goto out;
|
|
|
|
len -= BUF_PAGE_HDR_SIZE;
|
|
|
|
if (!data_page || !data_page->data)
|
|
goto out;
|
|
if (data_page->order != buffer->subbuf_order)
|
|
goto out;
|
|
|
|
bpage = data_page->data;
|
|
if (!bpage)
|
|
goto out;
|
|
|
|
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
|
|
|
|
reader = rb_get_reader_page(cpu_buffer);
|
|
if (!reader)
|
|
goto out_unlock;
|
|
|
|
event = rb_reader_event(cpu_buffer);
|
|
|
|
read = reader->read;
|
|
commit = rb_page_size(reader);
|
|
|
|
/* Check if any events were dropped */
|
|
missed_events = cpu_buffer->lost_events;
|
|
|
|
/*
|
|
* If this page has been partially read or
|
|
* if len is not big enough to read the rest of the page or
|
|
* a writer is still on the page, then
|
|
* we must copy the data from the page to the buffer.
|
|
* Otherwise, we can simply swap the page with the one passed in.
|
|
*/
|
|
if (read || (len < (commit - read)) ||
|
|
cpu_buffer->reader_page == cpu_buffer->commit_page ||
|
|
cpu_buffer->mapped) {
|
|
struct buffer_data_page *rpage = cpu_buffer->reader_page->page;
|
|
unsigned int rpos = read;
|
|
unsigned int pos = 0;
|
|
unsigned int size;
|
|
|
|
/*
|
|
* If a full page is expected, this can still be returned
|
|
* if there's been a previous partial read and the
|
|
* rest of the page can be read and the commit page is off
|
|
* the reader page.
|
|
*/
|
|
if (full &&
|
|
(!read || (len < (commit - read)) ||
|
|
cpu_buffer->reader_page == cpu_buffer->commit_page))
|
|
goto out_unlock;
|
|
|
|
if (len > (commit - read))
|
|
len = (commit - read);
|
|
|
|
/* Always keep the time extend and data together */
|
|
size = rb_event_ts_length(event);
|
|
|
|
if (len < size)
|
|
goto out_unlock;
|
|
|
|
/* save the current timestamp, since the user will need it */
|
|
save_timestamp = cpu_buffer->read_stamp;
|
|
|
|
/* Need to copy one event at a time */
|
|
do {
|
|
/* We need the size of one event, because
|
|
* rb_advance_reader only advances by one event,
|
|
* whereas rb_event_ts_length may include the size of
|
|
* one or two events.
|
|
* We have already ensured there's enough space if this
|
|
* is a time extend. */
|
|
size = rb_event_length(event);
|
|
memcpy(bpage->data + pos, rpage->data + rpos, size);
|
|
|
|
len -= size;
|
|
|
|
rb_advance_reader(cpu_buffer);
|
|
rpos = reader->read;
|
|
pos += size;
|
|
|
|
if (rpos >= commit)
|
|
break;
|
|
|
|
event = rb_reader_event(cpu_buffer);
|
|
/* Always keep the time extend and data together */
|
|
size = rb_event_ts_length(event);
|
|
} while (len >= size);
|
|
|
|
/* update bpage */
|
|
local_set(&bpage->commit, pos);
|
|
bpage->time_stamp = save_timestamp;
|
|
|
|
/* we copied everything to the beginning */
|
|
read = 0;
|
|
} else {
|
|
/* update the entry counter */
|
|
cpu_buffer->read += rb_page_entries(reader);
|
|
cpu_buffer->read_bytes += rb_page_size(reader);
|
|
|
|
/* swap the pages */
|
|
rb_init_page(bpage);
|
|
bpage = reader->page;
|
|
reader->page = data_page->data;
|
|
local_set(&reader->write, 0);
|
|
local_set(&reader->entries, 0);
|
|
reader->read = 0;
|
|
data_page->data = bpage;
|
|
|
|
/*
|
|
* Use the real_end for the data size,
|
|
* This gives us a chance to store the lost events
|
|
* on the page.
|
|
*/
|
|
if (reader->real_end)
|
|
local_set(&bpage->commit, reader->real_end);
|
|
}
|
|
ret = read;
|
|
|
|
cpu_buffer->lost_events = 0;
|
|
|
|
commit = local_read(&bpage->commit);
|
|
/*
|
|
* Set a flag in the commit field if we lost events
|
|
*/
|
|
if (missed_events) {
|
|
/* If there is room at the end of the page to save the
|
|
* missed events, then record it there.
|
|
*/
|
|
if (buffer->subbuf_size - commit >= sizeof(missed_events)) {
|
|
memcpy(&bpage->data[commit], &missed_events,
|
|
sizeof(missed_events));
|
|
local_add(RB_MISSED_STORED, &bpage->commit);
|
|
commit += sizeof(missed_events);
|
|
}
|
|
local_add(RB_MISSED_EVENTS, &bpage->commit);
|
|
}
|
|
|
|
/*
|
|
* This page may be off to user land. Zero it out here.
|
|
*/
|
|
if (commit < buffer->subbuf_size)
|
|
memset(&bpage->data[commit], 0, buffer->subbuf_size - commit);
|
|
|
|
out_unlock:
|
|
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
|
|
|
|
out:
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_read_page);
|
|
|
|
/**
|
|
* ring_buffer_read_page_data - get pointer to the data in the page.
|
|
* @page: the page to get the data from
|
|
*
|
|
* Returns pointer to the actual data in this page.
|
|
*/
|
|
void *ring_buffer_read_page_data(struct buffer_data_read_page *page)
|
|
{
|
|
return page->data;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_read_page_data);
|
|
|
|
/**
|
|
* ring_buffer_subbuf_size_get - get size of the sub buffer.
|
|
* @buffer: the buffer to get the sub buffer size from
|
|
*
|
|
* Returns size of the sub buffer, in bytes.
|
|
*/
|
|
int ring_buffer_subbuf_size_get(struct trace_buffer *buffer)
|
|
{
|
|
return buffer->subbuf_size + BUF_PAGE_HDR_SIZE;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_subbuf_size_get);
|
|
|
|
/**
|
|
* ring_buffer_subbuf_order_get - get order of system sub pages in one buffer page.
|
|
* @buffer: The ring_buffer to get the system sub page order from
|
|
*
|
|
* By default, one ring buffer sub page equals to one system page. This parameter
|
|
* is configurable, per ring buffer. The size of the ring buffer sub page can be
|
|
* extended, but must be an order of system page size.
|
|
*
|
|
* Returns the order of buffer sub page size, in system pages:
|
|
* 0 means the sub buffer size is 1 system page and so forth.
|
|
* In case of an error < 0 is returned.
|
|
*/
|
|
int ring_buffer_subbuf_order_get(struct trace_buffer *buffer)
|
|
{
|
|
if (!buffer)
|
|
return -EINVAL;
|
|
|
|
return buffer->subbuf_order;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_subbuf_order_get);
|
|
|
|
/**
|
|
* ring_buffer_subbuf_order_set - set the size of ring buffer sub page.
|
|
* @buffer: The ring_buffer to set the new page size.
|
|
* @order: Order of the system pages in one sub buffer page
|
|
*
|
|
* By default, one ring buffer pages equals to one system page. This API can be
|
|
* used to set new size of the ring buffer page. The size must be order of
|
|
* system page size, that's why the input parameter @order is the order of
|
|
* system pages that are allocated for one ring buffer page:
|
|
* 0 - 1 system page
|
|
* 1 - 2 system pages
|
|
* 3 - 4 system pages
|
|
* ...
|
|
*
|
|
* Returns 0 on success or < 0 in case of an error.
|
|
*/
|
|
int ring_buffer_subbuf_order_set(struct trace_buffer *buffer, int order)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
struct buffer_page *bpage, *tmp;
|
|
int old_order, old_size;
|
|
int nr_pages;
|
|
int psize;
|
|
int err;
|
|
int cpu;
|
|
|
|
if (!buffer || order < 0)
|
|
return -EINVAL;
|
|
|
|
if (buffer->subbuf_order == order)
|
|
return 0;
|
|
|
|
psize = (1 << order) * PAGE_SIZE;
|
|
if (psize <= BUF_PAGE_HDR_SIZE)
|
|
return -EINVAL;
|
|
|
|
/* Size of a subbuf cannot be greater than the write counter */
|
|
if (psize > RB_WRITE_MASK + 1)
|
|
return -EINVAL;
|
|
|
|
old_order = buffer->subbuf_order;
|
|
old_size = buffer->subbuf_size;
|
|
|
|
/* prevent another thread from changing buffer sizes */
|
|
mutex_lock(&buffer->mutex);
|
|
atomic_inc(&buffer->record_disabled);
|
|
|
|
/* Make sure all commits have finished */
|
|
synchronize_rcu();
|
|
|
|
buffer->subbuf_order = order;
|
|
buffer->subbuf_size = psize - BUF_PAGE_HDR_SIZE;
|
|
|
|
/* Make sure all new buffers are allocated, before deleting the old ones */
|
|
for_each_buffer_cpu(buffer, cpu) {
|
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
continue;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
|
|
if (cpu_buffer->mapped) {
|
|
err = -EBUSY;
|
|
goto error;
|
|
}
|
|
|
|
/* Update the number of pages to match the new size */
|
|
nr_pages = old_size * buffer->buffers[cpu]->nr_pages;
|
|
nr_pages = DIV_ROUND_UP(nr_pages, buffer->subbuf_size);
|
|
|
|
/* we need a minimum of two pages */
|
|
if (nr_pages < 2)
|
|
nr_pages = 2;
|
|
|
|
cpu_buffer->nr_pages_to_update = nr_pages;
|
|
|
|
/* Include the reader page */
|
|
nr_pages++;
|
|
|
|
/* Allocate the new size buffer */
|
|
INIT_LIST_HEAD(&cpu_buffer->new_pages);
|
|
if (__rb_allocate_pages(cpu_buffer, nr_pages,
|
|
&cpu_buffer->new_pages)) {
|
|
/* not enough memory for new pages */
|
|
err = -ENOMEM;
|
|
goto error;
|
|
}
|
|
}
|
|
|
|
for_each_buffer_cpu(buffer, cpu) {
|
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
continue;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
|
|
/* Clear the head bit to make the link list normal to read */
|
|
rb_head_page_deactivate(cpu_buffer);
|
|
|
|
/* Now walk the list and free all the old sub buffers */
|
|
list_for_each_entry_safe(bpage, tmp, cpu_buffer->pages, list) {
|
|
list_del_init(&bpage->list);
|
|
free_buffer_page(bpage);
|
|
}
|
|
/* The above loop stopped an the last page needing to be freed */
|
|
bpage = list_entry(cpu_buffer->pages, struct buffer_page, list);
|
|
free_buffer_page(bpage);
|
|
|
|
/* Free the current reader page */
|
|
free_buffer_page(cpu_buffer->reader_page);
|
|
|
|
/* One page was allocated for the reader page */
|
|
cpu_buffer->reader_page = list_entry(cpu_buffer->new_pages.next,
|
|
struct buffer_page, list);
|
|
list_del_init(&cpu_buffer->reader_page->list);
|
|
|
|
/* The cpu_buffer pages are a link list with no head */
|
|
cpu_buffer->pages = cpu_buffer->new_pages.next;
|
|
cpu_buffer->new_pages.next->prev = cpu_buffer->new_pages.prev;
|
|
cpu_buffer->new_pages.prev->next = cpu_buffer->new_pages.next;
|
|
|
|
/* Clear the new_pages list */
|
|
INIT_LIST_HEAD(&cpu_buffer->new_pages);
|
|
|
|
cpu_buffer->head_page
|
|
= list_entry(cpu_buffer->pages, struct buffer_page, list);
|
|
cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;
|
|
|
|
cpu_buffer->nr_pages = cpu_buffer->nr_pages_to_update;
|
|
cpu_buffer->nr_pages_to_update = 0;
|
|
|
|
free_pages((unsigned long)cpu_buffer->free_page, old_order);
|
|
cpu_buffer->free_page = NULL;
|
|
|
|
rb_head_page_activate(cpu_buffer);
|
|
|
|
rb_check_pages(cpu_buffer);
|
|
}
|
|
|
|
atomic_dec(&buffer->record_disabled);
|
|
mutex_unlock(&buffer->mutex);
|
|
|
|
return 0;
|
|
|
|
error:
|
|
buffer->subbuf_order = old_order;
|
|
buffer->subbuf_size = old_size;
|
|
|
|
atomic_dec(&buffer->record_disabled);
|
|
mutex_unlock(&buffer->mutex);
|
|
|
|
for_each_buffer_cpu(buffer, cpu) {
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
|
|
if (!cpu_buffer->nr_pages_to_update)
|
|
continue;
|
|
|
|
list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages, list) {
|
|
list_del_init(&bpage->list);
|
|
free_buffer_page(bpage);
|
|
}
|
|
}
|
|
|
|
return err;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_subbuf_order_set);
|
|
|
|
static int rb_alloc_meta_page(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
struct page *page;
|
|
|
|
if (cpu_buffer->meta_page)
|
|
return 0;
|
|
|
|
page = alloc_page(GFP_USER | __GFP_ZERO);
|
|
if (!page)
|
|
return -ENOMEM;
|
|
|
|
cpu_buffer->meta_page = page_to_virt(page);
|
|
|
|
return 0;
|
|
}
|
|
|
|
static void rb_free_meta_page(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
unsigned long addr = (unsigned long)cpu_buffer->meta_page;
|
|
|
|
free_page(addr);
|
|
cpu_buffer->meta_page = NULL;
|
|
}
|
|
|
|
static void rb_setup_ids_meta_page(struct ring_buffer_per_cpu *cpu_buffer,
|
|
unsigned long *subbuf_ids)
|
|
{
|
|
struct trace_buffer_meta *meta = cpu_buffer->meta_page;
|
|
unsigned int nr_subbufs = cpu_buffer->nr_pages + 1;
|
|
struct buffer_page *first_subbuf, *subbuf;
|
|
int id = 0;
|
|
|
|
subbuf_ids[id] = (unsigned long)cpu_buffer->reader_page->page;
|
|
cpu_buffer->reader_page->id = id++;
|
|
|
|
first_subbuf = subbuf = rb_set_head_page(cpu_buffer);
|
|
do {
|
|
if (WARN_ON(id >= nr_subbufs))
|
|
break;
|
|
|
|
subbuf_ids[id] = (unsigned long)subbuf->page;
|
|
subbuf->id = id;
|
|
|
|
rb_inc_page(&subbuf);
|
|
id++;
|
|
} while (subbuf != first_subbuf);
|
|
|
|
/* install subbuf ID to kern VA translation */
|
|
cpu_buffer->subbuf_ids = subbuf_ids;
|
|
|
|
meta->meta_page_size = PAGE_SIZE;
|
|
meta->meta_struct_len = sizeof(*meta);
|
|
meta->nr_subbufs = nr_subbufs;
|
|
meta->subbuf_size = cpu_buffer->buffer->subbuf_size + BUF_PAGE_HDR_SIZE;
|
|
|
|
rb_update_meta_page(cpu_buffer);
|
|
}
|
|
|
|
static struct ring_buffer_per_cpu *
|
|
rb_get_mapped_buffer(struct trace_buffer *buffer, int cpu)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
return ERR_PTR(-EINVAL);
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
|
|
mutex_lock(&cpu_buffer->mapping_lock);
|
|
|
|
if (!cpu_buffer->mapped) {
|
|
mutex_unlock(&cpu_buffer->mapping_lock);
|
|
return ERR_PTR(-ENODEV);
|
|
}
|
|
|
|
return cpu_buffer;
|
|
}
|
|
|
|
static void rb_put_mapped_buffer(struct ring_buffer_per_cpu *cpu_buffer)
|
|
{
|
|
mutex_unlock(&cpu_buffer->mapping_lock);
|
|
}
|
|
|
|
/*
|
|
* Fast-path for rb_buffer_(un)map(). Called whenever the meta-page doesn't need
|
|
* to be set-up or torn-down.
|
|
*/
|
|
static int __rb_inc_dec_mapped(struct ring_buffer_per_cpu *cpu_buffer,
|
|
bool inc)
|
|
{
|
|
unsigned long flags;
|
|
|
|
lockdep_assert_held(&cpu_buffer->mapping_lock);
|
|
|
|
if (inc && cpu_buffer->mapped == UINT_MAX)
|
|
return -EBUSY;
|
|
|
|
if (WARN_ON(!inc && cpu_buffer->mapped == 0))
|
|
return -EINVAL;
|
|
|
|
mutex_lock(&cpu_buffer->buffer->mutex);
|
|
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
|
|
|
|
if (inc)
|
|
cpu_buffer->mapped++;
|
|
else
|
|
cpu_buffer->mapped--;
|
|
|
|
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
|
|
mutex_unlock(&cpu_buffer->buffer->mutex);
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* +--------------+ pgoff == 0
|
|
* | meta page |
|
|
* +--------------+ pgoff == 1
|
|
* | subbuffer 0 |
|
|
* | |
|
|
* +--------------+ pgoff == (1 + (1 << subbuf_order))
|
|
* | subbuffer 1 |
|
|
* | |
|
|
* ...
|
|
*/
|
|
#ifdef CONFIG_MMU
|
|
static int __rb_map_vma(struct ring_buffer_per_cpu *cpu_buffer,
|
|
struct vm_area_struct *vma)
|
|
{
|
|
unsigned long nr_subbufs, nr_pages, vma_pages, pgoff = vma->vm_pgoff;
|
|
unsigned int subbuf_pages, subbuf_order;
|
|
struct page **pages;
|
|
int p = 0, s = 0;
|
|
int err;
|
|
|
|
/* Refuse MP_PRIVATE or writable mappings */
|
|
if (vma->vm_flags & VM_WRITE || vma->vm_flags & VM_EXEC ||
|
|
!(vma->vm_flags & VM_MAYSHARE))
|
|
return -EPERM;
|
|
|
|
/*
|
|
* Make sure the mapping cannot become writable later. Also tell the VM
|
|
* to not touch these pages (VM_DONTCOPY | VM_DONTEXPAND).
|
|
*/
|
|
vm_flags_mod(vma, VM_DONTCOPY | VM_DONTEXPAND | VM_DONTDUMP,
|
|
VM_MAYWRITE);
|
|
|
|
lockdep_assert_held(&cpu_buffer->mapping_lock);
|
|
|
|
subbuf_order = cpu_buffer->buffer->subbuf_order;
|
|
subbuf_pages = 1 << subbuf_order;
|
|
|
|
nr_subbufs = cpu_buffer->nr_pages + 1; /* + reader-subbuf */
|
|
nr_pages = ((nr_subbufs) << subbuf_order) - pgoff + 1; /* + meta-page */
|
|
|
|
vma_pages = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
|
|
if (!vma_pages || vma_pages > nr_pages)
|
|
return -EINVAL;
|
|
|
|
nr_pages = vma_pages;
|
|
|
|
pages = kcalloc(nr_pages, sizeof(*pages), GFP_KERNEL);
|
|
if (!pages)
|
|
return -ENOMEM;
|
|
|
|
if (!pgoff) {
|
|
pages[p++] = virt_to_page(cpu_buffer->meta_page);
|
|
|
|
/*
|
|
* TODO: Align sub-buffers on their size, once
|
|
* vm_insert_pages() supports the zero-page.
|
|
*/
|
|
} else {
|
|
/* Skip the meta-page */
|
|
pgoff--;
|
|
|
|
if (pgoff % subbuf_pages) {
|
|
err = -EINVAL;
|
|
goto out;
|
|
}
|
|
|
|
s += pgoff / subbuf_pages;
|
|
}
|
|
|
|
while (p < nr_pages) {
|
|
struct page *page = virt_to_page((void *)cpu_buffer->subbuf_ids[s]);
|
|
int off = 0;
|
|
|
|
if (WARN_ON_ONCE(s >= nr_subbufs)) {
|
|
err = -EINVAL;
|
|
goto out;
|
|
}
|
|
|
|
for (; off < (1 << (subbuf_order)); off++, page++) {
|
|
if (p >= nr_pages)
|
|
break;
|
|
|
|
pages[p++] = page;
|
|
}
|
|
s++;
|
|
}
|
|
|
|
err = vm_insert_pages(vma, vma->vm_start, pages, &nr_pages);
|
|
|
|
out:
|
|
kfree(pages);
|
|
|
|
return err;
|
|
}
|
|
#else
|
|
static int __rb_map_vma(struct ring_buffer_per_cpu *cpu_buffer,
|
|
struct vm_area_struct *vma)
|
|
{
|
|
return -EOPNOTSUPP;
|
|
}
|
|
#endif
|
|
|
|
int ring_buffer_map(struct trace_buffer *buffer, int cpu,
|
|
struct vm_area_struct *vma)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
unsigned long flags, *subbuf_ids;
|
|
int err = 0;
|
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
return -EINVAL;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
|
|
mutex_lock(&cpu_buffer->mapping_lock);
|
|
|
|
if (cpu_buffer->mapped) {
|
|
err = __rb_map_vma(cpu_buffer, vma);
|
|
if (!err)
|
|
err = __rb_inc_dec_mapped(cpu_buffer, true);
|
|
mutex_unlock(&cpu_buffer->mapping_lock);
|
|
return err;
|
|
}
|
|
|
|
/* prevent another thread from changing buffer/sub-buffer sizes */
|
|
mutex_lock(&buffer->mutex);
|
|
|
|
err = rb_alloc_meta_page(cpu_buffer);
|
|
if (err)
|
|
goto unlock;
|
|
|
|
/* subbuf_ids include the reader while nr_pages does not */
|
|
subbuf_ids = kcalloc(cpu_buffer->nr_pages + 1, sizeof(*subbuf_ids), GFP_KERNEL);
|
|
if (!subbuf_ids) {
|
|
rb_free_meta_page(cpu_buffer);
|
|
err = -ENOMEM;
|
|
goto unlock;
|
|
}
|
|
|
|
atomic_inc(&cpu_buffer->resize_disabled);
|
|
|
|
/*
|
|
* Lock all readers to block any subbuf swap until the subbuf IDs are
|
|
* assigned.
|
|
*/
|
|
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
|
|
rb_setup_ids_meta_page(cpu_buffer, subbuf_ids);
|
|
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
|
|
|
|
err = __rb_map_vma(cpu_buffer, vma);
|
|
if (!err) {
|
|
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
|
|
cpu_buffer->mapped = 1;
|
|
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
|
|
} else {
|
|
kfree(cpu_buffer->subbuf_ids);
|
|
cpu_buffer->subbuf_ids = NULL;
|
|
rb_free_meta_page(cpu_buffer);
|
|
}
|
|
|
|
unlock:
|
|
mutex_unlock(&buffer->mutex);
|
|
mutex_unlock(&cpu_buffer->mapping_lock);
|
|
|
|
return err;
|
|
}
|
|
|
|
int ring_buffer_unmap(struct trace_buffer *buffer, int cpu)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
unsigned long flags;
|
|
int err = 0;
|
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
return -EINVAL;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
|
|
mutex_lock(&cpu_buffer->mapping_lock);
|
|
|
|
if (!cpu_buffer->mapped) {
|
|
err = -ENODEV;
|
|
goto out;
|
|
} else if (cpu_buffer->mapped > 1) {
|
|
__rb_inc_dec_mapped(cpu_buffer, false);
|
|
goto out;
|
|
}
|
|
|
|
mutex_lock(&buffer->mutex);
|
|
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
|
|
|
|
cpu_buffer->mapped = 0;
|
|
|
|
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
|
|
|
|
kfree(cpu_buffer->subbuf_ids);
|
|
cpu_buffer->subbuf_ids = NULL;
|
|
rb_free_meta_page(cpu_buffer);
|
|
atomic_dec(&cpu_buffer->resize_disabled);
|
|
|
|
mutex_unlock(&buffer->mutex);
|
|
|
|
out:
|
|
mutex_unlock(&cpu_buffer->mapping_lock);
|
|
|
|
return err;
|
|
}
|
|
|
|
int ring_buffer_map_get_reader(struct trace_buffer *buffer, int cpu)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
struct buffer_page *reader;
|
|
unsigned long missed_events;
|
|
unsigned long reader_size;
|
|
unsigned long flags;
|
|
|
|
cpu_buffer = rb_get_mapped_buffer(buffer, cpu);
|
|
if (IS_ERR(cpu_buffer))
|
|
return (int)PTR_ERR(cpu_buffer);
|
|
|
|
raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
|
|
|
|
consume:
|
|
if (rb_per_cpu_empty(cpu_buffer))
|
|
goto out;
|
|
|
|
reader_size = rb_page_size(cpu_buffer->reader_page);
|
|
|
|
/*
|
|
* There are data to be read on the current reader page, we can
|
|
* return to the caller. But before that, we assume the latter will read
|
|
* everything. Let's update the kernel reader accordingly.
|
|
*/
|
|
if (cpu_buffer->reader_page->read < reader_size) {
|
|
while (cpu_buffer->reader_page->read < reader_size)
|
|
rb_advance_reader(cpu_buffer);
|
|
goto out;
|
|
}
|
|
|
|
reader = rb_get_reader_page(cpu_buffer);
|
|
if (WARN_ON(!reader))
|
|
goto out;
|
|
|
|
/* Check if any events were dropped */
|
|
missed_events = cpu_buffer->lost_events;
|
|
|
|
if (cpu_buffer->reader_page != cpu_buffer->commit_page) {
|
|
if (missed_events) {
|
|
struct buffer_data_page *bpage = reader->page;
|
|
unsigned int commit;
|
|
/*
|
|
* Use the real_end for the data size,
|
|
* This gives us a chance to store the lost events
|
|
* on the page.
|
|
*/
|
|
if (reader->real_end)
|
|
local_set(&bpage->commit, reader->real_end);
|
|
/*
|
|
* If there is room at the end of the page to save the
|
|
* missed events, then record it there.
|
|
*/
|
|
commit = rb_page_size(reader);
|
|
if (buffer->subbuf_size - commit >= sizeof(missed_events)) {
|
|
memcpy(&bpage->data[commit], &missed_events,
|
|
sizeof(missed_events));
|
|
local_add(RB_MISSED_STORED, &bpage->commit);
|
|
}
|
|
local_add(RB_MISSED_EVENTS, &bpage->commit);
|
|
}
|
|
} else {
|
|
/*
|
|
* There really shouldn't be any missed events if the commit
|
|
* is on the reader page.
|
|
*/
|
|
WARN_ON_ONCE(missed_events);
|
|
}
|
|
|
|
cpu_buffer->lost_events = 0;
|
|
|
|
goto consume;
|
|
|
|
out:
|
|
/* Some archs do not have data cache coherency between kernel and user-space */
|
|
flush_dcache_folio(virt_to_folio(cpu_buffer->reader_page->page));
|
|
|
|
rb_update_meta_page(cpu_buffer);
|
|
|
|
raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
|
|
rb_put_mapped_buffer(cpu_buffer);
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* We only allocate new buffers, never free them if the CPU goes down.
|
|
* If we were to free the buffer, then the user would lose any trace that was in
|
|
* the buffer.
|
|
*/
|
|
int trace_rb_cpu_prepare(unsigned int cpu, struct hlist_node *node)
|
|
{
|
|
struct trace_buffer *buffer;
|
|
long nr_pages_same;
|
|
int cpu_i;
|
|
unsigned long nr_pages;
|
|
|
|
buffer = container_of(node, struct trace_buffer, node);
|
|
if (cpumask_test_cpu(cpu, buffer->cpumask))
|
|
return 0;
|
|
|
|
nr_pages = 0;
|
|
nr_pages_same = 1;
|
|
/* check if all cpu sizes are same */
|
|
for_each_buffer_cpu(buffer, cpu_i) {
|
|
/* fill in the size from first enabled cpu */
|
|
if (nr_pages == 0)
|
|
nr_pages = buffer->buffers[cpu_i]->nr_pages;
|
|
if (nr_pages != buffer->buffers[cpu_i]->nr_pages) {
|
|
nr_pages_same = 0;
|
|
break;
|
|
}
|
|
}
|
|
/* allocate minimum pages, user can later expand it */
|
|
if (!nr_pages_same)
|
|
nr_pages = 2;
|
|
buffer->buffers[cpu] =
|
|
rb_allocate_cpu_buffer(buffer, nr_pages, cpu);
|
|
if (!buffer->buffers[cpu]) {
|
|
WARN(1, "failed to allocate ring buffer on CPU %u\n",
|
|
cpu);
|
|
return -ENOMEM;
|
|
}
|
|
smp_wmb();
|
|
cpumask_set_cpu(cpu, buffer->cpumask);
|
|
return 0;
|
|
}
|
|
|
|
#ifdef CONFIG_RING_BUFFER_STARTUP_TEST
|
|
/*
|
|
* This is a basic integrity check of the ring buffer.
|
|
* Late in the boot cycle this test will run when configured in.
|
|
* It will kick off a thread per CPU that will go into a loop
|
|
* writing to the per cpu ring buffer various sizes of data.
|
|
* Some of the data will be large items, some small.
|
|
*
|
|
* Another thread is created that goes into a spin, sending out
|
|
* IPIs to the other CPUs to also write into the ring buffer.
|
|
* this is to test the nesting ability of the buffer.
|
|
*
|
|
* Basic stats are recorded and reported. If something in the
|
|
* ring buffer should happen that's not expected, a big warning
|
|
* is displayed and all ring buffers are disabled.
|
|
*/
|
|
static struct task_struct *rb_threads[NR_CPUS] __initdata;
|
|
|
|
struct rb_test_data {
|
|
struct trace_buffer *buffer;
|
|
unsigned long events;
|
|
unsigned long bytes_written;
|
|
unsigned long bytes_alloc;
|
|
unsigned long bytes_dropped;
|
|
unsigned long events_nested;
|
|
unsigned long bytes_written_nested;
|
|
unsigned long bytes_alloc_nested;
|
|
unsigned long bytes_dropped_nested;
|
|
int min_size_nested;
|
|
int max_size_nested;
|
|
int max_size;
|
|
int min_size;
|
|
int cpu;
|
|
int cnt;
|
|
};
|
|
|
|
static struct rb_test_data rb_data[NR_CPUS] __initdata;
|
|
|
|
/* 1 meg per cpu */
|
|
#define RB_TEST_BUFFER_SIZE 1048576
|
|
|
|
static char rb_string[] __initdata =
|
|
"abcdefghijklmnopqrstuvwxyz1234567890!@#$%^&*()?+\\"
|
|
"?+|:';\",.<>/?abcdefghijklmnopqrstuvwxyz1234567890"
|
|
"!@#$%^&*()?+\\?+|:';\",.<>/?abcdefghijklmnopqrstuv";
|
|
|
|
static bool rb_test_started __initdata;
|
|
|
|
struct rb_item {
|
|
int size;
|
|
char str[];
|
|
};
|
|
|
|
static __init int rb_write_something(struct rb_test_data *data, bool nested)
|
|
{
|
|
struct ring_buffer_event *event;
|
|
struct rb_item *item;
|
|
bool started;
|
|
int event_len;
|
|
int size;
|
|
int len;
|
|
int cnt;
|
|
|
|
/* Have nested writes different that what is written */
|
|
cnt = data->cnt + (nested ? 27 : 0);
|
|
|
|
/* Multiply cnt by ~e, to make some unique increment */
|
|
size = (cnt * 68 / 25) % (sizeof(rb_string) - 1);
|
|
|
|
len = size + sizeof(struct rb_item);
|
|
|
|
started = rb_test_started;
|
|
/* read rb_test_started before checking buffer enabled */
|
|
smp_rmb();
|
|
|
|
event = ring_buffer_lock_reserve(data->buffer, len);
|
|
if (!event) {
|
|
/* Ignore dropped events before test starts. */
|
|
if (started) {
|
|
if (nested)
|
|
data->bytes_dropped += len;
|
|
else
|
|
data->bytes_dropped_nested += len;
|
|
}
|
|
return len;
|
|
}
|
|
|
|
event_len = ring_buffer_event_length(event);
|
|
|
|
if (RB_WARN_ON(data->buffer, event_len < len))
|
|
goto out;
|
|
|
|
item = ring_buffer_event_data(event);
|
|
item->size = size;
|
|
memcpy(item->str, rb_string, size);
|
|
|
|
if (nested) {
|
|
data->bytes_alloc_nested += event_len;
|
|
data->bytes_written_nested += len;
|
|
data->events_nested++;
|
|
if (!data->min_size_nested || len < data->min_size_nested)
|
|
data->min_size_nested = len;
|
|
if (len > data->max_size_nested)
|
|
data->max_size_nested = len;
|
|
} else {
|
|
data->bytes_alloc += event_len;
|
|
data->bytes_written += len;
|
|
data->events++;
|
|
if (!data->min_size || len < data->min_size)
|
|
data->max_size = len;
|
|
if (len > data->max_size)
|
|
data->max_size = len;
|
|
}
|
|
|
|
out:
|
|
ring_buffer_unlock_commit(data->buffer);
|
|
|
|
return 0;
|
|
}
|
|
|
|
static __init int rb_test(void *arg)
|
|
{
|
|
struct rb_test_data *data = arg;
|
|
|
|
while (!kthread_should_stop()) {
|
|
rb_write_something(data, false);
|
|
data->cnt++;
|
|
|
|
set_current_state(TASK_INTERRUPTIBLE);
|
|
/* Now sleep between a min of 100-300us and a max of 1ms */
|
|
usleep_range(((data->cnt % 3) + 1) * 100, 1000);
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
static __init void rb_ipi(void *ignore)
|
|
{
|
|
struct rb_test_data *data;
|
|
int cpu = smp_processor_id();
|
|
|
|
data = &rb_data[cpu];
|
|
rb_write_something(data, true);
|
|
}
|
|
|
|
static __init int rb_hammer_test(void *arg)
|
|
{
|
|
while (!kthread_should_stop()) {
|
|
|
|
/* Send an IPI to all cpus to write data! */
|
|
smp_call_function(rb_ipi, NULL, 1);
|
|
/* No sleep, but for non preempt, let others run */
|
|
schedule();
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
static __init int test_ringbuffer(void)
|
|
{
|
|
struct task_struct *rb_hammer;
|
|
struct trace_buffer *buffer;
|
|
int cpu;
|
|
int ret = 0;
|
|
|
|
if (security_locked_down(LOCKDOWN_TRACEFS)) {
|
|
pr_warn("Lockdown is enabled, skipping ring buffer tests\n");
|
|
return 0;
|
|
}
|
|
|
|
pr_info("Running ring buffer tests...\n");
|
|
|
|
buffer = ring_buffer_alloc(RB_TEST_BUFFER_SIZE, RB_FL_OVERWRITE);
|
|
if (WARN_ON(!buffer))
|
|
return 0;
|
|
|
|
/* Disable buffer so that threads can't write to it yet */
|
|
ring_buffer_record_off(buffer);
|
|
|
|
for_each_online_cpu(cpu) {
|
|
rb_data[cpu].buffer = buffer;
|
|
rb_data[cpu].cpu = cpu;
|
|
rb_data[cpu].cnt = cpu;
|
|
rb_threads[cpu] = kthread_run_on_cpu(rb_test, &rb_data[cpu],
|
|
cpu, "rbtester/%u");
|
|
if (WARN_ON(IS_ERR(rb_threads[cpu]))) {
|
|
pr_cont("FAILED\n");
|
|
ret = PTR_ERR(rb_threads[cpu]);
|
|
goto out_free;
|
|
}
|
|
}
|
|
|
|
/* Now create the rb hammer! */
|
|
rb_hammer = kthread_run(rb_hammer_test, NULL, "rbhammer");
|
|
if (WARN_ON(IS_ERR(rb_hammer))) {
|
|
pr_cont("FAILED\n");
|
|
ret = PTR_ERR(rb_hammer);
|
|
goto out_free;
|
|
}
|
|
|
|
ring_buffer_record_on(buffer);
|
|
/*
|
|
* Show buffer is enabled before setting rb_test_started.
|
|
* Yes there's a small race window where events could be
|
|
* dropped and the thread wont catch it. But when a ring
|
|
* buffer gets enabled, there will always be some kind of
|
|
* delay before other CPUs see it. Thus, we don't care about
|
|
* those dropped events. We care about events dropped after
|
|
* the threads see that the buffer is active.
|
|
*/
|
|
smp_wmb();
|
|
rb_test_started = true;
|
|
|
|
set_current_state(TASK_INTERRUPTIBLE);
|
|
/* Just run for 10 seconds */;
|
|
schedule_timeout(10 * HZ);
|
|
|
|
kthread_stop(rb_hammer);
|
|
|
|
out_free:
|
|
for_each_online_cpu(cpu) {
|
|
if (!rb_threads[cpu])
|
|
break;
|
|
kthread_stop(rb_threads[cpu]);
|
|
}
|
|
if (ret) {
|
|
ring_buffer_free(buffer);
|
|
return ret;
|
|
}
|
|
|
|
/* Report! */
|
|
pr_info("finished\n");
|
|
for_each_online_cpu(cpu) {
|
|
struct ring_buffer_event *event;
|
|
struct rb_test_data *data = &rb_data[cpu];
|
|
struct rb_item *item;
|
|
unsigned long total_events;
|
|
unsigned long total_dropped;
|
|
unsigned long total_written;
|
|
unsigned long total_alloc;
|
|
unsigned long total_read = 0;
|
|
unsigned long total_size = 0;
|
|
unsigned long total_len = 0;
|
|
unsigned long total_lost = 0;
|
|
unsigned long lost;
|
|
int big_event_size;
|
|
int small_event_size;
|
|
|
|
ret = -1;
|
|
|
|
total_events = data->events + data->events_nested;
|
|
total_written = data->bytes_written + data->bytes_written_nested;
|
|
total_alloc = data->bytes_alloc + data->bytes_alloc_nested;
|
|
total_dropped = data->bytes_dropped + data->bytes_dropped_nested;
|
|
|
|
big_event_size = data->max_size + data->max_size_nested;
|
|
small_event_size = data->min_size + data->min_size_nested;
|
|
|
|
pr_info("CPU %d:\n", cpu);
|
|
pr_info(" events: %ld\n", total_events);
|
|
pr_info(" dropped bytes: %ld\n", total_dropped);
|
|
pr_info(" alloced bytes: %ld\n", total_alloc);
|
|
pr_info(" written bytes: %ld\n", total_written);
|
|
pr_info(" biggest event: %d\n", big_event_size);
|
|
pr_info(" smallest event: %d\n", small_event_size);
|
|
|
|
if (RB_WARN_ON(buffer, total_dropped))
|
|
break;
|
|
|
|
ret = 0;
|
|
|
|
while ((event = ring_buffer_consume(buffer, cpu, NULL, &lost))) {
|
|
total_lost += lost;
|
|
item = ring_buffer_event_data(event);
|
|
total_len += ring_buffer_event_length(event);
|
|
total_size += item->size + sizeof(struct rb_item);
|
|
if (memcmp(&item->str[0], rb_string, item->size) != 0) {
|
|
pr_info("FAILED!\n");
|
|
pr_info("buffer had: %.*s\n", item->size, item->str);
|
|
pr_info("expected: %.*s\n", item->size, rb_string);
|
|
RB_WARN_ON(buffer, 1);
|
|
ret = -1;
|
|
break;
|
|
}
|
|
total_read++;
|
|
}
|
|
if (ret)
|
|
break;
|
|
|
|
ret = -1;
|
|
|
|
pr_info(" read events: %ld\n", total_read);
|
|
pr_info(" lost events: %ld\n", total_lost);
|
|
pr_info(" total events: %ld\n", total_lost + total_read);
|
|
pr_info(" recorded len bytes: %ld\n", total_len);
|
|
pr_info(" recorded size bytes: %ld\n", total_size);
|
|
if (total_lost) {
|
|
pr_info(" With dropped events, record len and size may not match\n"
|
|
" alloced and written from above\n");
|
|
} else {
|
|
if (RB_WARN_ON(buffer, total_len != total_alloc ||
|
|
total_size != total_written))
|
|
break;
|
|
}
|
|
if (RB_WARN_ON(buffer, total_lost + total_read != total_events))
|
|
break;
|
|
|
|
ret = 0;
|
|
}
|
|
if (!ret)
|
|
pr_info("Ring buffer PASSED!\n");
|
|
|
|
ring_buffer_free(buffer);
|
|
return 0;
|
|
}
|
|
|
|
late_initcall(test_ringbuffer);
|
|
#endif /* CONFIG_RING_BUFFER_STARTUP_TEST */
|