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The commit:
commit e0fdace10e
Author: David Miller <davem@davemloft.net>
Date: Fri Aug 1 01:11:22 2008 -0700
debug_locks: set oops_in_progress if we will log messages.
Otherwise lock debugging messages on runqueue locks can deadlock the
system due to the wakeups performed by printk().
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Will permanently set oops_in_progress on any lockdep failure.
When this triggers it will cause any read from the ring buffer to
permanently disable the ring buffer (not to mention no locking of
printk).
This patch removes the check. It keeps the print in NMI which makes
sense. This is probably OK, since the ring buffer should not cause
something to set oops_in_progress anyway.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The function ring_buffer_discard_commit inversed the code path
of the result of try_to_discard. It should skip incrementing the
entry counter if try_to_discard succeeded. But instead, it increments
the entry conder if it succeeded to discard, and does not increment
it if it fails.
The result of this bug is that filtering will make the stat counters
incorrect.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
About a half events are missing when we splice_read
from trace_pipe. They are unexpectedly consumed because we ignore
the TRACE_TYPE_NO_CONSUME return value used by the function graph
tracer when it needs to consume the events by itself to walk on
the ring buffer.
The same problem appears with ftrace_dump()
Example of an output before this patch:
1) | ktime_get_real() {
1) 2.846 us | read_hpet();
1) 4.558 us | }
1) 6.195 us | }
After this patch:
0) | ktime_get_real() {
0) | getnstimeofday() {
0) 1.960 us | read_hpet();
0) 3.597 us | }
0) 5.196 us | }
The fix also applies on 2.6.30
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: stable@kernel.org
LKML-Reference: <4A6EEC52.90704@cn.fujitsu.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
When print_graph_entry() computes a function call entry event, it needs
to also check the next entry to guess if it matches the return event of
the current function entry.
In order to look at this next event, it needs to consume the current
entry before going ahead in the ring buffer.
However, if the current event that gets consumed is the last one in the
ring buffer head page, the ring_buffer may reuse the page for writers.
The consumed entry will then become invalid because of possible
racy overwriting.
Me must then handle this entry by making a copy of it.
The fix also applies on 2.6.30
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: stable@kernel.org
LKML-Reference: <4A6EEAEC.3050508@cn.fujitsu.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
The current code will truncate the ftrace files contents if O_APPEND
is not set and the file is opened in write mode. This is incorrect.
It should only truncate the file if O_TRUNC is set. Otherwise
if one of these files is opened by a C program with fopen "r+",
it will incorrectly truncate the file.
Reported-by: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Since the trace_printk may use pointers to the format fields
in the buffer, they are exported via debugfs/tracing/printk_formats.
This is used by utilities that read the ring buffer in binary format.
It helps the utilities map the address of the format in the binary
buffer to what the printf format looks like.
Unfortunately, the way the output code works, it exports the address
of the pointer to the format address, and not the format address
itself. This makes the file totally useless in trying to figure
out what format string a binary address belongs to.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Every time we cat a trace_stat file, we leak memory allocated by
seq_open().
Also fix memory leak in a failure path in tracing_stat_open().
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <4A67D92B.4060704@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Every time we cat set_graph_function, we leak memory allocated
by seq_open().
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <4A67D907.2010500@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Every time we cat stack_trace, we leak memory allocated by seq_open().
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <4A67D8E8.3020500@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Currently a subsystem filter should be applicable to all events
under the subsystem, and if it failed, all the event filters
will be cleared. Those behaviors make subsys filter much less
useful:
# echo 'vec == 1' > irq/softirq_entry/filter
# echo 'irq == 5' > irq/filter
bash: echo: write error: Invalid argument
# cat irq/softirq_entry/filter
none
I'd expect it set the filter for irq_handler_entry/exit, and
not touch softirq_entry/exit.
The basic idea is, try to see if the filter can be applied
to which events, and then just apply to the those events:
# echo 'vec == 1' > softirq_entry/filter
# echo 'irq == 5' > filter
# cat irq_handler_entry/filter
irq == 5
# cat softirq_entry/filter
vec == 1
Changelog for v2:
- do some cleanups to address Frederic's comments.
Inspired-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4A63D485.7030703@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
'\n' is already appended, and what we need is just an extra
space for the '\0'.
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
LKML-Reference: <4A3EED63.3090908@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
When a dynamic array is defined, we add __data_loc_foo in
trace_entry to record the offset of the array, but the
size of the array is not recorded, which causes 2 problems:
- the event filter just compares the first 2 chars of the strings.
- parsers can't parse dynamic arrays.
So we encode the size of each dynamic array in the higher 16 bits
of __data_loc_foo, while the offset is in lower 16 bits.
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <4A5E964A.9000403@cn.fujitsu.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
We can directly use %pf input format instead of kallsyms_lookup()
and %s input format
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Reviewed-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
We can directly use %pF input format instead of sprint_symbol()
and %s input format.
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Reviewed-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Rewrite the __ftrace_replace_code() function, simplify it, but don't
change the code's logic.
First, we get the state we want to set, if the record has the same
state, then do nothing, otherwise enable/disable it.
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Reviewed-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
ftrace_trace_onoff_callback() will return an error even if we do the
right operation, for example:
# echo _spin_*:traceon:10 > set_ftrace_filter
-bash: echo: write error: Invalid argument
# cat set_ftrace_filter
#### all functions enabled ####
_spin_trylock_bh:traceon:count=10
_spin_unlock_irq:traceon:count=10
_spin_unlock_bh:traceon:count=10
_spin_lock_irq:traceon:count=10
_spin_unlock:traceon:count=10
_spin_trylock:traceon:count=10
_spin_unlock_irqrestore:traceon:count=10
_spin_lock_irqsave:traceon:count=10
_spin_lock_bh:traceon:count=10
_spin_lock:traceon:count=10
We want to set _spin_*:traceon:10 to set_ftrace_filter, it complains
with "Invalid argument", but the operation is successful.
This is because ftrace_process_regex() returns the number of functions that
matched the pattern. If the number is not 0, this value is returned
by ftrace_regex_write() whereas we want to return the number of bytes
virtually written.
Also the file offset pointer is not updated in this case.
If the number of matched functions is lower than the number of bytes written
by the user, this results to a reprocessing of the string given by the user with
a lower size, leading to a malformed ftrace regex and then a -EINVAL returned.
So, this patch fixes it by returning 0 if no error occured.
The fix also applies on 2.6.30
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Reviewed-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: stable@kernel.org
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
kernel/trace/ring_buffer.c: In function 'rb_tail_page_update':
kernel/trace/ring_buffer.c:849: warning: value computed is not used
kernel/trace/ring_buffer.c:850: warning: value computed is not used
Add "(void)"s to fix this warning, because we don't need here to handle
the fail case of cmpxchg, it's fine if an interrupt already did the
job.
Changed from V1:
Add a comment(which is written by Steven) for it.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
The per cpu variable stat is freeded if we fail to allocate a name
on start up. This was due to stat at first being allocated in the
initial design. But since then, it has become a static per cpu variable
but the free on error was not removed.
Also added __init annotation to the function that this is in.
[ Impact: prevent possible memory corruption on low mem at boot up ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
* Remove smp_lock.h from files which don't need it (including some headers!)
* Add smp_lock.h to files which do need it
* Make smp_lock.h include conditional in hardirq.h
It's needed only for one kernel_locked() usage which is under CONFIG_PREEMPT
This will make hardirq.h inclusion cheaper for every PREEMPT=n config
(which includes allmodconfig/allyesconfig, BTW)
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The stat entries can be freed when the stat file is being read.
The worse is, the ptr can be freed immediately after it's returned
from workqueue_stat_start/next().
Add a refcnt to struct cpu_workqueue_stats to avoid use-after-free.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <4A51B16F.6010608@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Add stat_release() callback to struct tracer_stat, so a stat tracer
can release it's entries after the stat file has been read out.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4A51B16A.6020708@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
So we have:
- kmemtrace_print_alloc/free() for kmemtrace default output
- kmemtrace_print_alloc/free_user() for binary output used
by kmemtrace-user.
Suggested-by: Eduard - Gabriel Munteanu <eduard.munteanu@linux360.ro>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4A51B288.70505@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Remove the obsolete seq_print_ip_sym() usage and replace it
by the %pf format in order to print function symbols.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Reviewed-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Eduard - Gabriel Munteanu <eduard.munteanu@linux360.ro>
LKML-Reference: <1247107590-6428-3-git-send-email-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Remove the obsolete seq_print_ip_sym() usage and replace it
by the %pf format in order to print function symbols.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Reviewed-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
LKML-Reference: <1247107590-6428-2-git-send-email-fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Remove empty subsystem and its directory when module unload.
Before patch:
# rmmod trace-events-sample.ko
# ls sample
enable filter
After patch:
# rmmod trace-events-sample.ko
# ls sample
ls: cannot access sample: No such file or directory
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Acked-by: Tom Zanussi <tzanussi@gmail.com>
Reviewed-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <4A55A8BE.9010707@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
No need to save preds to event_subsystem, because it's not used.
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Acked-by: Tom Zanussi <tzanussi@gmail.com>
Reviewed-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <4A55A83C.1030005@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This patch converts the ring buffers into a completely lockless
buffer recording system. The read side still takes locks since
we still serialize readers. But the writers are the ones that
must be lockless (those can happen in NMIs).
The main change is to the "head_page" pointer. We write to the
tail, and read from the head. The "head_page" pointer in the cpu
buffer is now just a reference to where to look. The real head
page is now kept in the head_page->list->prev->next pointer.
That is, in the list head of the previous page we set flags.
The list pages are allocated to be aligned such that the lowest
significant bits are always zero pointing to the list. This gives
us play to put in flags to their pointers.
bit 0: set when the page is a head page
bit 1: set when the writer is moving the page (for overwrite mode)
cmpxchg is used to update the pointer.
When the writer wraps the buffer and the tail meets the head,
in overwrite mode, the writer must move the head page forward.
It first uses cmpxchg to change the pointer flag from 1 to 2.
Once this is done, the reader on another CPU will not take the
page from the buffer.
The writers need to protect against interrupts (we don't bother with
disabling interrupts because NMIs are allowed to write too).
After the writer sets the pointer flag to 2, it takes care to
manage interrupts coming in. This is discribed in detail within the
comments of the code.
Changes in version 2:
- Let reader reset entries value of header page.
- Fix tail page passing commit page on reader page test.
- Always increment entries and write counter in rb_tail_page_update
- Add safety check in rb_set_commit_to_write to break out of infinite loop
- add mask in rb_is_reader_page
[ Impact: lock free writing to the ring buffer ]
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
This patch changes the ring buffer data pages from using a link list
head pointer, to making each buffer page point to another buffer page
and never back to a "head".
This makes the handling of the ring buffer less complex, since the
traversing of the ring buffer pages no longer needs to account for the
head pointer.
This change also is needed to make the ring buffer lockless.
[
Changes in version 2:
- Added change that Lai Jiangshan mentioned.
From: Lai Jiangshan <laijs@cn.fujitsu.com>
Date: Thu, 11 Jun 2009 11:25:48 +0800
LKML-Reference: <4A30793C.6090208@cn.fujitsu.com>
I'm not sure whether these 4 lines:
bpage = list_entry(pages.next, struct buffer_page, list);
list_del_init(&bpage->list);
cpu_buffer->pages = &bpage->list;
list_splice(&pages, cpu_buffer->pages);
equal to these 2 lines:
cpu_buffer->pages = pages.next;
list_del(&pages);
If there are equivalent, I think the second one
are simpler. It may be not a really necessarily cleanup.
What I asked is: if there are equivalent, could you use these two line:
cpu_buffer->pages = pages.next;
list_del(&pages);
]
[ Impact: simplify the ring buffer to help make it lockless ]
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Pull linus#master to merge PER_CPU_DEF_ATTRIBUTES and alpha build fix
changes. As alpha in percpu tree uses 'weak' attribute instead of
inline assembly, there's no need for __used attribute.
Conflicts:
arch/alpha/include/asm/percpu.h
arch/mn10300/kernel/vmlinux.lds.S
include/linux/percpu-defs.h
Currently by default the output of kmemtrace is binary format instead
of human-readable output.
This patch makes the following changes:
- We'll see human-readable output by default
- We'll see binary output if 'bin' option is set
Note: you may probably need to explicitly disable context-info binary
output:
# echo 0 > options/context-info
# echo 1 > options/bin
# cat trace_pipe
v2:
- use %pF to print call_site
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Pekka Enberg <penberg@cs.helsinki.fi>
Acked-by: Eduard - Gabriel Munteanu <eduard.munteanu@linux360.ro>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4A4DD0A0.5060500@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
We will lose something if trace_seq->buffer[0] is 0, because the copy length
is calculated by strlen() in seq_puts(), so using seq_write() instead of
seq_puts().
There have a example:
after reboot:
# echo kmemtrace > current_tracer
# echo 0 > options/kmem_minimalistic
# cat trace
# tracer: kmemtrace
#
#
Nothing is exported, because the first byte of trace_seq->buffer[ ]
is KMEMTRACE_USER_ALLOC.
( the value of KMEMTRACE_USER_ALLOC is zero, seeing
kmemtrace_print_alloc_user() in kernel/trace/kmemtrace.c)
Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Pekka Enberg <penberg@cs.helsinki.fi>
Acked-by: Eduard - Gabriel Munteanu <eduard.munteanu@linux360.ro>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <4A4B2351.5010300@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
We already have ftrace= boot option, and this adds a similar
boot option for trace events, so allow trace events to be
enabled at boot, for boot debugging purpose.
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4A4ACE29.3010407@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
To use boot tracer, one should pass initcall_debug as well as
ftrace=initcall to the command line.
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <4A48735E.9050002@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Some fields for struct ftrace_graph_ret are missed
when they are exported to user.
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <4A448FB6.5000302@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This made my machine completely frozen:
# echo 1 > /proc/sys/kernel/stack_tracer_enabled
# echo 2 > /proc/sys/kernel/stack_tracer_enabled
The cause is register_ftrace_function() was called twice.
Also fix ftrace_enabled sysctl, though seems nothing bad happened
as I tested it.
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4A448D17.9010305@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
The first entry of the ftrace profile was always skipped when
reading trace_stat/functionX.
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4A443D59.4080307@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
In hunting down the cause for the hwlat_detector ring buffer spew in
my failed -next builds it became obvious that folks are now treating
ring_buffer as something that is generic independent of tracing and thus,
suitable for public driver consumption.
Given that there are only a few minor areas in ring_buffer that have any
reliance on CONFIG_TRACING or CONFIG_FUNCTION_TRACER, provide stubs for
those and make it generally available.
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
Cc: Jon Masters <jcm@jonmasters.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <20090625053012.GB19944@linux-sh.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
We should be able to specify [KMG] when setting trace_buf_size
boot option, as documented in kernel-parameters.txt
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4A41F2DB.4020102@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
When the output of set_ftrace_filter is larger than PAGE_SIZE,
t_hash_start() will be called the 2nd time, and then we start
from the head of a hlist, which is wrong and causes some entries
to be outputed twice.
The worse is, if the hlist is large enough, reading set_ftrace_filter
won't stop but in a dead loop.
Reviewed-by: Liming Wang <liming.wang@windriver.com>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4A41876E.2060407@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
It's rather confusing that in t_start(), in some cases @pos is
incremented, and in some cases it's decremented and then incremented.
This patch rewrites t_start() in a much more general way.
Thus we fix a bug that if ftrace_filtered == 1, functions have tracer
hooks won't be printed, because the branch is always unreachable:
static void *t_start(...)
{
...
if (!p)
return t_hash_start(m, pos);
return p;
}
Before:
# echo 'sys_open' > /mnt/tracing/set_ftrace_filter
# echo 'sys_write:traceon:4' >> /mnt/tracing/set_ftrace_filter
sys_open
After:
# echo 'sys_open' > /mnt/tracing/set_ftrace_filter
# echo 'sys_write:traceon:4' >> /mnt/tracing/set_ftrace_filter
sys_open
sys_write:traceon:count=4
Reviewed-by: Liming Wang <liming.wang@windriver.com>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4A41874B.4090507@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
It's wrong to increment @pos in g_start(). It causes some entries
lost when reading set_graph_function, if the output of the file
is larger than PAGE_SIZE.
Reviewed-by: Liming Wang <liming.wang@windriver.com>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4A418738.7090401@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
The iterator is m->private, but it's not reset to trace_types in
t_start(). If the output is larger than PAGE_SIZE and t_start()
is called the 2nd time, things will go wrong.
Reviewed-by: Liming Wang <liming.wang@windriver.com>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4A418728.5020506@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
It's wrong to increment @pos in stat_seq_start(). It causes some
stat entries lost when reading stat file, if the output of the file
is larger than PAGE_SIZE.
Reviewed-by: Liming Wang <liming.wang@windriver.com>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4A418716.90209@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
It's wrong to increment @pos in t_start(), otherwise we'll lose
some entries when reading printk_formats, if the output is larger
than PAGE_SIZE.
Reported-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Reviewed-by: Liming Wang <liming.wang@windriver.com>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4A4186FA.1020106@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
While testing syscall tracepoints posted by Jason, I found 3 entries
were missing when reading available_events. The output size of
available_events is < 4 pages, which means we lost 1 entry per page.
The cause is, it's wrong to increment @pos in s_start().
Actually there's another bug here -- reading avaiable_events/set_events
can race with module unload:
# cat available_events |
s_start() |
s_stop() |
| # rmmod foo.ko
s_start() |
call = list_entry(m->private) |
@call might be freed and accessing it will lead to crash.
Reviewed-by: Liming Wang <liming.wang@windriver.com>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4A4186DD.6090405@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Percpu variable definition is about to be updated such that all percpu
symbols including the static ones must be unique. Update percpu
variable definitions accordingly.
* as,cfq: rename ioc_count uniquely
* cpufreq: rename cpu_dbs_info uniquely
* xen: move nesting_count out of xen_evtchn_do_upcall() and rename it
* mm: move ratelimits out of balance_dirty_pages_ratelimited_nr() and
rename it
* ipv4,6: rename cookie_scratch uniquely
* x86 perf_counter: rename prev_left to pmc_prev_left, irq_entry to
pmc_irq_entry and nmi_entry to pmc_nmi_entry
* perf_counter: rename disable_count to perf_disable_count
* ftrace: rename test_event_disable to ftrace_test_event_disable
* kmemleak: rename test_pointer to kmemleak_test_pointer
* mce: rename next_interval to mce_next_interval
[ Impact: percpu usage cleanups, no duplicate static percpu var names ]
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Christoph Lameter <cl@linux-foundation.org>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: Dave Jones <davej@redhat.com>
Cc: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: linux-mm <linux-mm@kvack.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Steven Rostedt <srostedt@redhat.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Andi Kleen <andi@firstfloor.org>
* 'tracing-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (24 commits)
tracing/urgent: warn in case of ftrace_start_up inbalance
tracing/urgent: fix unbalanced ftrace_start_up
function-graph: add stack frame test
function-graph: disable when both x86_32 and optimize for size are configured
ring-buffer: have benchmark test print to trace buffer
ring-buffer: do not grab locks in nmi
ring-buffer: add locks around rb_per_cpu_empty
ring-buffer: check for less than two in size allocation
ring-buffer: remove useless compile check for buffer_page size
ring-buffer: remove useless warn on check
ring-buffer: use BUF_PAGE_HDR_SIZE in calculating index
tracing: update sample event documentation
tracing/filters: fix race between filter setting and module unload
tracing/filters: free filter_string in destroy_preds()
ring-buffer: use commit counters for commit pointer accounting
ring-buffer: remove unused variable
ring-buffer: have benchmark test handle discarded events
ring-buffer: prevent adding write in discarded area
tracing/filters: strloc should be unsigned short
tracing/filters: operand can be negative
...
Fix up kmemcheck-induced conflict in kernel/trace/ring_buffer.c manually
Prevent from further ftrace_start_up inbalances so that we avoid
future nop patching omissions with dynamic ftrace.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Perfcounter reports the following stats for a wide system
profiling:
#
# (2364 samples)
#
# Overhead Symbol
# ........ ......
#
15.40% [k] mwait_idle_with_hints
8.29% [k] read_hpet
5.75% [k] ftrace_caller
3.60% [k] ftrace_call
[...]
This snapshot has been taken while neither the function tracer nor
the function graph tracer was running.
With dynamic ftrace, such results show a wrong ftrace behaviour
because all calls to ftrace_caller or ftrace_graph_caller (the patched
calls to mcount) are supposed to be patched into nop if none of those
tracers are running.
The problem occurs after the first run of the function tracer. Once we
launch it a second time, the callsites will never be nopped back,
unless you set custom filters.
For example it happens during the self tests at boot time.
The function tracer selftest runs, and then the dynamic tracing is
tested too. After that, the callsites are left un-nopped.
This is because the reset callback of the function tracer tries to
unregister two ftrace callbacks in once: the common function tracer
and the function tracer with stack backtrace, regardless of which
one is currently in use.
It then creates an unbalance on ftrace_start_up value which is expected
to be zero when the last ftrace callback is unregistered. When it
reaches zero, the FTRACE_DISABLE_CALLS is set on the next ftrace
command, triggering the patching into nop. But since it becomes
unbalanced, ie becomes lower than zero, if the kernel functions
are patched again (as in every further function tracer runs), they
won't ever be nopped back.
Note that ftrace_call and ftrace_graph_call are still patched back
to ftrace_stub in the off case, but not the callers of ftrace_call
and ftrace_graph_caller. It means that the tracing is well deactivated
but we waste a useless call into every kernel function.
This patch just unregisters the right ftrace_ops for the function
tracer on its reset callback and ignores the other one which is
not registered, fixing the unbalance. The problem also happens
is .30
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: stable@kernel.org
In case gcc does something funny with the stack frames, or the return
from function code, we would like to detect that.
An arch may implement passing of a variable that is unique to the
function and can be saved on entering a function and can be tested
when exiting the function. Usually the frame pointer can be used for
this purpose.
This patch also implements this for x86. Where it passes in the stack
frame of the parent function, and will test that frame on exit.
There was a case in x86_32 with optimize for size (-Os) where, for a
few functions, gcc would align the stack frame and place a copy of the
return address into it. The function graph tracer modified the copy and
not the actual return address. On return from the funtion, it did not go
to the tracer hook, but returned to the parent. This broke the function
graph tracer, because the return of the parent (where gcc did not do
this funky manipulation) returned to the location that the child function
was suppose to. This caused strange kernel crashes.
This test detected the problem and pointed out where the issue was.
This modifies the parameters of one of the functions that the arch
specific code calls, so it includes changes to arch code to accommodate
the new prototype.
Note, I notice that the parsic arch implements its own push_return_trace.
This is now a generic function and the ftrace_push_return_trace should be
used instead. This patch does not touch that code.
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Helge Deller <deller@gmx.de>
Cc: Kyle McMartin <kyle@mcmartin.ca>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
On x86_32, when optimize for size is set, gcc may align the frame pointer
and make a copy of the the return address inside the stack frame.
The return address that is located in the stack frame may not be
the one used to return to the calling function. This will break the
function graph tracer.
The function graph tracer replaces the return address with a jump to a hook
function that can trace the exit of the function. If it only replaces
a copy, then the hook will not be called when the function returns.
Worse yet, when the parent function returns, the function graph tracer
will return back to the location of the child function which will
easily crash the kernel with weird results.
To see the problem, when i386 is compiled with -Os we get:
c106be03: 57 push %edi
c106be04: 8d 7c 24 08 lea 0x8(%esp),%edi
c106be08: 83 e4 e0 and $0xffffffe0,%esp
c106be0b: ff 77 fc pushl 0xfffffffc(%edi)
c106be0e: 55 push %ebp
c106be0f: 89 e5 mov %esp,%ebp
c106be11: 57 push %edi
c106be12: 56 push %esi
c106be13: 53 push %ebx
c106be14: 81 ec 8c 00 00 00 sub $0x8c,%esp
c106be1a: e8 f5 57 fb ff call c1021614 <mcount>
When it is compiled with -O2 instead we get:
c10896f0: 55 push %ebp
c10896f1: 89 e5 mov %esp,%ebp
c10896f3: 83 ec 28 sub $0x28,%esp
c10896f6: 89 5d f4 mov %ebx,0xfffffff4(%ebp)
c10896f9: 89 75 f8 mov %esi,0xfffffff8(%ebp)
c10896fc: 89 7d fc mov %edi,0xfffffffc(%ebp)
c10896ff: e8 d0 08 fa ff call c1029fd4 <mcount>
The compile with -Os will align the stack pointer then set up the
frame pointer (%ebp), and it copies the return address back into
the stack frame. The change to the return address in mcount is done
to the copy and not the real place holder of the return address.
Then compile with -O2 sets up the frame pointer first, this makes
the change to the return address by mcount affect where the function
will jump on exit.
Reported-by: Jake Edge <jake@lwn.net>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Currently the output of the ring buffer benchmark/test prints to
the console. This test runs for ten seconds every ten seconds and
ouputs the result after every iteration. This needlessly fills up
the logs.
This patch makes the ring buffer benchmark/test print to the ftrace
buffer using trace_printk. To view the test results, you must examine
the debug/tracing/trace file.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
If ftrace_dump_on_oops is set, and an NMI detects a lockup, then it
will need to read from the ring buffer. But the read side of the
ring buffer still takes locks. This patch adds a check on the read
side that if it is in an NMI, then it will disable the ring buffer
and not take any locks.
Reads can still happen on a disabled ring buffer.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The checking of whether the buffer is empty or not needs to be serialized
among the readers. Add the reader spin lock around it.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The ring buffer must have at least two pages allocated for the
reader page swap to work.
The page count check will miss the case of a zero size passed in.
Even though a zero size ring buffer would probably fail an allocation,
making the min size check for less than two instead of equal to one makes
the code a bit more robust.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The original version of the ring buffer had a hack to map the
page struct that held the pages of the buffer to also be the structure
that the ring buffer would keep the pages in a link list.
This overlap of the page struct was very dangerous and that hack was
removed a while ago.
But there was a check to make sure the buffer_page never became bigger
than the page struct, and would fail the compile if it did. The
check was only meaningful when we had the hack. Now that we have separate
allocated descriptors for the buffer pages, we can remove this check.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
A check if "write > BUF_PAGE_SIZE" is done right after a
if (write > BUF_PAGE_SIZE)
return ...;
Thus the check is actually testing the compiler and not the
kernel. This is useless, remove it.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The index of the event is found by masking PAGE_MASK to it and
subtracting the header size. Currently the header size is calculate
by PAGE_SIZE - BUF_PAGE_SIZE, when we already have a macro
BUF_PAGE_HDR_SIZE to define it.
If we want to change BUF_PAGE_SIZE to something less than filling
the rest of the page (this is done for debugging), then we break
the algorithm to find the index.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Module unload is protected by event_mutex, while setting filter is
protected by filter_mutex. This leads to the race:
echo 'bar == 0 || bar == 10' \ |
> sample/filter |
| insmod sample.ko
add_pred("bar == 0") |
-> n_preds == 1 |
add_pred("bar == 100") |
-> n_preds == 2 |
| rmmod sample.ko
| insmod sample.ko
add_pred("&&") |
-> n_preds == 1 (should be 3) |
Now event->filter->preds is corrupted. An then when filter_match_preds()
is called, the WARN_ON() in it will be triggered.
To avoid the race, we remove filter_mutex, and replace it with event_mutex.
[ Impact: prevent corruption of filters by module removing and loading ]
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <4A375A4D.6000205@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The ring buffer is made up of three sets of pointers.
The head page pointer, which points to the next page for the reader to
get.
The commit pointer and commit index, which points to the page and index
of the last committed write respectively.
The tail pointer and tail index, which points to the page and the index
of the last reserved data respectively (non committed).
The commit pointer is only moved forward by the outer most writer.
If a nested writer comes in, it will not move the pointer forward.
The current implementation has a flaw. It assumes that the outer most
writer successfully reserved data. There's a small race window where
the outer most writer could find the tail pointer, but a nested
writer could come in (via interrupt) and move the tail forward, and
even the commit forward.
The outer writer would not realized the commit moved forward and the
accounting will break.
This patch changes the design to use counters in the per cpu buffers
to keep track of commits. The counters are incremented at the start
of the commit, and decremented at the end. If the end commit counter
is 1, then it moves the commit pointers. A loop is made to check for
races between checking and moving the commit pointers. Only the outer
commit should move the pointers anyway.
The test of knowing if a reserve is equal to the last commit update
is still needed to know for time keeping. The time code is much less
racey than the commit updates.
This change not only solves the mentioned race, but also makes the
code simpler.
[ Impact: fix commit race and simplify code ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Fix the compiler error:
kernel/trace/ring_buffer.c: In function 'rb_move_tail':
kernel/trace/ring_buffer.c:1236: warning: unused variable 'event'
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
With the addition of commit:
c7b0930857
ring-buffer: prevent adding write in discarded area
The ring buffer may now add discarded events when a write passes
the end of a buffer page. Before, a discarded event was only added
when the tracer deliberately created one. The ring buffer benchmark
test does not handle discarded events when it reads the buffer and
fails when it encounters one.
Also fix the increment for large data entries (luckily, the test did
not add any yet).
[ Impact: fix false failure of ring buffer self test ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Many developers use "/debug/" or "/debugfs/" or "/sys/kernel/debug/"
directory name to mount debugfs filesystem for ftrace according to
./Documentation/tracers/ftrace.txt file.
And, three directory names(ex:/debug/, /debugfs/, /sys/kernel/debug/) is
existed in kernel source like ftrace, DRM, Wireless, Documentation,
Network[sky2]files to mount debugfs filesystem.
debugfs means debug filesystem for debugging easy to use by greg kroah
hartman. "/sys/kernel/debug/" name is suitable as directory name
of debugfs filesystem.
- debugfs related reference: http://lwn.net/Articles/334546/
Fix inconsistency of directory name to mount debugfs filesystem.
* From Steven Rostedt
- find_debugfs() and tracing_files() in this patch.
Signed-off-by: GeunSik Lim <geunsik.lim@samsung.com>
Acked-by : Inaky Perez-Gonzalez <inaky@linux.intel.com>
Reviewed-by : Steven Rostedt <rostedt@goodmis.org>
Reviewed-by : James Smart <james.smart@emulex.com>
CC: Jiri Kosina <trivial@kernel.org>
CC: David Airlie <airlied@linux.ie>
CC: Peter Osterlund <petero2@telia.com>
CC: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
CC: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
CC: Masami Hiramatsu <mhiramat@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
* 'timers-for-linus-migration' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
timers: Logic to move non pinned timers
timers: /proc/sys sysctl hook to enable timer migration
timers: Identifying the existing pinned timers
timers: Framework for identifying pinned timers
timers: allow deferrable timers for intervals tv2-tv5 to be deferred
Fix up conflicts in kernel/sched.c and kernel/timer.c manually
This a very tight race where an interrupt could come in and not
have enough data to put into the end of a buffer page, and that
it would fail to write and need to go to the next page.
But if this happened when another writer was about to reserver
their data, and that writer has smaller data to reserve, then
it could succeed even though the interrupt moved the tail page.
To pervent that, if we fail to store data, and by subtracting the
amount we reserved we still have room for smaller data, we need
to fill that space with "discarded" data.
[ Impact: prevent race were buffer data may be lost ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
I forgot to update filter code accordingly in
"tracing/events: change the type of __str_loc_item to unsigned short"
(commt b0aae68cc5)
It can cause system crash:
# echo 1 > tracing/events/irq/irq_handler_entry/enable
# echo 'name == eth0' > tracing/events/irq/irq_handler_entry/filter
[ Impact: fix crash while filtering on __string() field ]
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <4A35B905.3090500@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Atomic allocation is not needed here.
[ Impact: clean up of memory alloction type ]
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <4A35B898.2050607@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
It's tracing_cpumask_new that should be kfree()ed.
This causes tracing_cpumask to be freed due to the typo:
# echo z > tracing_cpumask
bash: echo: write error: Invalid argument
And subsequent reads/writes to tracing_cpuamsk will access this
already-freed tracing_cpumask, thus may lead to crash.
[ Impact: fix leak and crash when writing invalid val to tracing_cpumask ]
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <4A35B86A.7070608@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
LKML-Reference: <200906122115.30787.rusty@rustcorp.com.au>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This gets rid of a heap of false-positive warnings from the tracer
code due to the use of bitfields.
[rebased for mainline inclusion]
Signed-off-by: Vegard Nossum <vegard.nossum@gmail.com>
* 'for-2.6.31' of git://git.kernel.dk/linux-2.6-block: (153 commits)
block: add request clone interface (v2)
floppy: fix hibernation
ramdisk: remove long-deprecated "ramdisk=" boot-time parameter
fs/bio.c: add missing __user annotation
block: prevent possible io_context->refcount overflow
Add serial number support for virtio_blk, V4a
block: Add missing bounce_pfn stacking and fix comments
Revert "block: Fix bounce limit setting in DM"
cciss: decode unit attention in SCSI error handling code
cciss: Remove no longer needed sendcmd reject processing code
cciss: change SCSI error handling routines to work with interrupts enabled.
cciss: separate error processing and command retrying code in sendcmd_withirq_core()
cciss: factor out fix target status processing code from sendcmd functions
cciss: simplify interface of sendcmd() and sendcmd_withirq()
cciss: factor out core of sendcmd_withirq() for use by SCSI error handling code
cciss: Use schedule_timeout_uninterruptible in SCSI error handling code
block: needs to set the residual length of a bidi request
Revert "block: implement blkdev_readpages"
block: Fix bounce limit setting in DM
Removed reference to non-existing file Documentation/PCI/PCI-DMA-mapping.txt
...
Manually fix conflicts with tracing updates in:
block/blk-sysfs.c
drivers/ide/ide-atapi.c
drivers/ide/ide-cd.c
drivers/ide/ide-floppy.c
drivers/ide/ide-tape.c
include/trace/events/block.h
kernel/trace/blktrace.c
* 'tracing-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
function-graph: always initialize task ret_stack
function-graph: move initialization of new tasks up in fork
function-graph: add memory barriers for accessing task's ret_stack
function-graph: enable the stack after initialization of other variables
function-graph: only allocate init tasks if it was not already done
Manually fix trivial conflict in kernel/trace/ftrace.c
* 'tracing-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip: (244 commits)
Revert "x86, bts: reenable ptrace branch trace support"
tracing: do not translate event helper macros in print format
ftrace/documentation: fix typo in function grapher name
tracing/events: convert block trace points to TRACE_EVENT(), fix !CONFIG_BLOCK
tracing: add protection around module events unload
tracing: add trace_seq_vprint interface
tracing: fix the block trace points print size
tracing/events: convert block trace points to TRACE_EVENT()
ring-buffer: fix ret in rb_add_time_stamp
ring-buffer: pass in lockdep class key for reader_lock
tracing: add annotation to what type of stack trace is recorded
tracing: fix multiple use of __print_flags and __print_symbolic
tracing/events: fix output format of user stack
tracing/events: fix output format of kernel stack
tracing/trace_stack: fix the number of entries in the header
ring-buffer: discard timestamps that are at the start of the buffer
ring-buffer: try to discard unneeded timestamps
ring-buffer: fix bug in ring_buffer_discard_commit
ftrace: do not profile functions when disabled
tracing: make trace pipe recognize latency format flag
...
When reading the trace buffer, there is a race that when a module
is unloaded it removes events that is stilled referenced in the buffers.
This patch adds the protection around the unloading of the events
from modules and the reading of the trace buffers.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The code to update the print formats for events requires a vprintf
format in the trace_seq. This patch adds that interface.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
TRACE_EVENT is a more generic way to define tracepoints. Doing so adds
these new capabilities to this tracepoint:
- zero-copy and per-cpu splice() tracing
- binary tracing without printf overhead
- structured logging records exposed under /debug/tracing/events
- trace events embedded in function tracer output and other plugins
- user-defined, per tracepoint filter expressions
...
Cons:
- no dev_t info for the output of plug, unplug_timer and unplug_io events.
no dev_t info for getrq and sleeprq events if bio == NULL.
no dev_t info for rq_abort,...,rq_requeue events if rq->rq_disk == NULL.
This is mainly because we can't get the deivce from a request queue.
But this may change in the future.
- A packet command is converted to a string in TP_assign, not TP_print.
While blktrace do the convertion just before output.
Since pc requests should be rather rare, this is not a big issue.
- In blktrace, an event can have 2 different print formats, but a TRACE_EVENT
has a unique format, which means we have some unused data in a trace entry.
The overhead is minimized by using __dynamic_array() instead of __array().
I've benchmarked the ioctl blktrace vs the splice based TRACE_EVENT tracing:
dd dd + ioctl blktrace dd + TRACE_EVENT (splice)
1 7.36s, 42.7 MB/s 7.50s, 42.0 MB/s 7.41s, 42.5 MB/s
2 7.43s, 42.3 MB/s 7.48s, 42.1 MB/s 7.43s, 42.4 MB/s
3 7.38s, 42.6 MB/s 7.45s, 42.2 MB/s 7.41s, 42.5 MB/s
So the overhead of tracing is very small, and no regression when using
those trace events vs blktrace.
And the binary output of TRACE_EVENT is much smaller than blktrace:
# ls -l -h
-rw-r--r-- 1 root root 8.8M 06-09 13:24 sda.blktrace.0
-rw-r--r-- 1 root root 195K 06-09 13:24 sda.blktrace.1
-rw-r--r-- 1 root root 2.7M 06-09 13:25 trace_splice.out
Following are some comparisons between TRACE_EVENT and blktrace:
plug:
kjournald-480 [000] 303.084981: block_plug: [kjournald]
kjournald-480 [000] 303.084981: 8,0 P N [kjournald]
unplug_io:
kblockd/0-118 [000] 300.052973: block_unplug_io: [kblockd/0] 1
kblockd/0-118 [000] 300.052974: 8,0 U N [kblockd/0] 1
remap:
kjournald-480 [000] 303.085042: block_remap: 8,0 W 102736992 + 8 <- (8,8) 33384
kjournald-480 [000] 303.085043: 8,0 A W 102736992 + 8 <- (8,8) 33384
bio_backmerge:
kjournald-480 [000] 303.085086: block_bio_backmerge: 8,0 W 102737032 + 8 [kjournald]
kjournald-480 [000] 303.085086: 8,0 M W 102737032 + 8 [kjournald]
getrq:
kjournald-480 [000] 303.084974: block_getrq: 8,0 W 102736984 + 8 [kjournald]
kjournald-480 [000] 303.084975: 8,0 G W 102736984 + 8 [kjournald]
bash-2066 [001] 1072.953770: 8,0 G N [bash]
bash-2066 [001] 1072.953773: block_getrq: 0,0 N 0 + 0 [bash]
rq_complete:
konsole-2065 [001] 300.053184: block_rq_complete: 8,0 W () 103669040 + 16 [0]
konsole-2065 [001] 300.053191: 8,0 C W 103669040 + 16 [0]
ksoftirqd/1-7 [001] 1072.953811: 8,0 C N (5a 00 08 00 00 00 00 00 24 00) [0]
ksoftirqd/1-7 [001] 1072.953813: block_rq_complete: 0,0 N (5a 00 08 00 00 00 00 00 24 00) 0 + 0 [0]
rq_insert:
kjournald-480 [000] 303.084985: block_rq_insert: 8,0 W 0 () 102736984 + 8 [kjournald]
kjournald-480 [000] 303.084986: 8,0 I W 102736984 + 8 [kjournald]
Changelog from v2 -> v3:
- use the newly introduced __dynamic_array().
Changelog from v1 -> v2:
- use __string() instead of __array() to minimize the memory required
to store hex dump of rq->cmd().
- support large pc requests.
- add missing blk_fill_rwbs_rq() in block_rq_requeue TRACE_EVENT.
- some cleanups.
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <4A2DF669.5070905@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The update of ret got mistakenly added to the if statement of
rb_try_to_discard. The variable ret should be 1 on commit and zero
otherwise.
[ Impact: fix compiler warning and real bug ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
On Sun, 7 Jun 2009, Ingo Molnar wrote:
> Testing tracer sched_switch: <6>Starting ring buffer hammer
> PASSED
> Testing tracer sysprof: PASSED
> Testing tracer function: PASSED
> Testing tracer irqsoff:
> =============================================
> PASSED
> Testing tracer preemptoff: PASSED
> Testing tracer preemptirqsoff: [ INFO: possible recursive locking detected ]
> PASSED
> Testing tracer branch: 2.6.30-rc8-tip-01972-ge5b9078-dirty #5760
> ---------------------------------------------
> rb_consumer/431 is trying to acquire lock:
> (&cpu_buffer->reader_lock){......}, at: [<c109eef7>] ring_buffer_reset_cpu+0x37/0x70
>
> but task is already holding lock:
> (&cpu_buffer->reader_lock){......}, at: [<c10a019e>] ring_buffer_consume+0x7e/0xc0
>
> other info that might help us debug this:
> 1 lock held by rb_consumer/431:
> #0: (&cpu_buffer->reader_lock){......}, at: [<c10a019e>] ring_buffer_consume+0x7e/0xc0
The ring buffer is a generic structure, and can be used outside of
ftrace. If ftrace traces within the use of the ring buffer, it can produce
false positives with lockdep.
This patch passes in a static lock key into the allocation of the ring
buffer, so that different ring buffers will have their own lock class.
Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1244477919.13761.9042.camel@twins>
[ store key in ring buffer descriptor ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The current method of printing out a stack trace is to add a new line
and print out the trace:
yum-updatesd-3120 [002] 573.691303:
=> do_softirq
=> irq_exit
=> smp_apic_timer_interrupt
=> apic_timer_interrupt
This looks a bit awkward, and if we have both stack and user stack traces
running, it would be nice to have a title to tell them apart, although
it is easy to tell by the output.
This patch adds an annotation to the start of the stack traces:
init-1 [003] 929.304979: <stack trace>
=> user_path_at
=> vfs_fstatat
=> vfs_stat
=> sys_newstat
=> system_call_fastpath
cat-3459 [002] 1016.824040: <user stack trace>
=> <0000003aae6c0250>
=> <00007ffff4b06ae4>
=> <69636172742f6775>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Here is an updated patch to include the extra call to
trace_seq_init() as requested. This is vs. the latest
-tip tree and fixes the use of multiple __print_flags
and __print_symbolic in a single tracer. Also tested
to ensure its working now:
mount.gfs2-2534 [000] 235.850587: gfs2_glock_queue: 8.7 glock 1:2 dequeue PR
mount.gfs2-2534 [000] 235.850591: gfs2_demote_rq: 8.7 glock 1:0 demote EX to NL flags:DI
mount.gfs2-2534 [000] 235.850591: gfs2_glock_queue: 8.7 glock 1:0 dequeue EX
glock_workqueue-2529 [000] 235.850666: gfs2_glock_state_change: 8.7 glock 1:0 state EX => NL tgt:NL dmt:NL flags:lDpI
glock_workqueue-2529 [000] 235.850672: gfs2_glock_put: 8.7 glock 1:0 state NL => IV flags:I
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
LKML-Reference: <1244037123.29604.603.camel@localhost.localdomain>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
According to "events/ftrace/user_stack/format", fix the output of
user stack.
before fix:
sh-1073 [000] 31.137561: <b7f274fe> <- <0804e33c> <- <080835c1>
after fix:
sh-1072 [000] 37.039329:
=> <b7f8a4fe>
=> <0804e33c>
=> <080835c1>
Signed-off-by: walimis <walimisdev@gmail.com>
LKML-Reference: <1244016090-7814-3-git-send-email-walimisdev@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
According to "events/ftrace/kernel_stack/format", output format of
kernel stack should use "=>" instead of "<=".
The second problem is that we shouldn't skip the first entry in the stack,
although it seems to be duplicated when used in the "function" tracer,
but events also use it. If we skip the first one, we will drop the topmost
entry of the stack.
The last problem is that if the last entry is ULONG_MAX(0xffffffff), we should
drop it, otherwise it will print a NULL name line.
before fix:
sh-1072 [000] 26.957239: sched_process_fork: parent sh:1072 child sh:1073
sh-1072 [000] 26.957262:
<= syscall_call
<=
sh-1072 [000] 26.957744: sched_switch: task sh:1072 [120] (R) ==> sh:1073 [120]
sh-1072 [000] 26.957752:
<= preempt_schedule
<= wake_up_new_task
<= do_fork
<= sys_clone
<= syscall_call
<=
After fix:
sh-1075 [000] 39.791848: sched_process_fork: parent sh:1075 child sh:1076
sh-1075 [000] 39.791871:
=> sys_clone
=> syscall_call
sh-1075 [000] 39.792713: sched_switch: task sh:1075 [120] (R) ==> sh:1076 [120]
sh-1075 [000] 39.792722:
=> schedule
=> preempt_schedule
=> wake_up_new_task
=> do_fork
=> sys_clone
=> syscall_call
Signed-off-by: walimis <walimisdev@gmail.com>
LKML-Reference: <1244016090-7814-2-git-send-email-walimisdev@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The last entry in the stack_dump_trace is ULONG_MAX, which is not
a valid entry, but max_stack_trace.nr_entries has accounted for it.
So when printing the header, we should decrease it by one.
Before fix, print as following, for example:
Depth Size Location (53 entries) <--- should be 52
----- ---- --------
0) 3264 108 update_wall_time+0x4d5/0x9a0
...
51) 80 80 syscall_call+0x7/0xb
^^^
it's correct.
Signed-off-by: walimis <walimisdev@gmail.com>
LKML-Reference: <1244016090-7814-1-git-send-email-walimisdev@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Every buffer page in the ring buffer includes its own time stamp.
When an event is recorded to the ring buffer with a delta time greater
than what can be held in the event header, a time stamp event is created.
If the the create timestamp falls over to the next buffer page, it is
redundant because the buffer page holds a full time stamp. This patch
will try to discard the time stamp when it falls to the start of the
next page.
This change also fixes a issues with disarding events. If most events are
discarded, timestamps will start to creep into the ring buffer. If we
do not discard the timestamps then they can fill up the ring buffer over
time and waste space.
This change will keep time stamps from filling up over another page. If
something is recorded in the buffer page, and the rest is filtered, then
the time stamps can only fill up to the end of the page.
[ Impact: prevent time stamps from filling ring buffer ]
Reported-by: Tim Bird <tim.bird@am.sony.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
There are times that a race may happen that we add a timestamp in a
nested write. This timestamp would just contain a zero delta and serves
no purpose.
Now that we have a way to discard events, this patch will try to discard
the timestamp instead of just wasting the space in the ring buffer.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
There's a bug in ring_buffer_discard_commit. The wrong
pointer is being compared in order to check if the event
can be freed from the buffer rather than discarded
(i.e. marked as PAD).
I noticed this when I was working on duration filtering.
The bug is not deadly - it just results in lots of wasted
space in the buffer. All filtered events are left in
the buffer and marked as discarded, rather than being
removed from the buffer to make space for other events.
Unfortunately, when I fixed this bug, I got errors doing a
filtered function trace. Multiple TIME_EXTEND
events pile up in the buffer, and trigger the
following loop overage warning in rb_iter_peek():
again:
...
if (RB_WARN_ON(cpu_buffer, ++nr_loops > 10))
return NULL;
I'm not sure what the best way is to fix this. I don't
know if I should extend the loop threshhold, or if I should
make the test more complex (ignore TIME_EXTEND
events), or just get rid of this loop check completely.
Note that if I implement a workaround for this, then I
see another problem from rb_advance_iter(). I haven't
tracked that one down yet.
In general, it seems like the case of removing filtered
events has not been working properly, and so some assumptions
about buffer invariant conditions need to be revisited.
Here's the patch for the simple fix:
Compare correct pointer for checking if an event can be
freed rather than left as discarded in the buffer.
Signed-off-by: Tim Bird <tim.bird@am.sony.com>
LKML-Reference: <4A25BE9E.5090909@am.sony.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
On creating a new task while running the function graph tracer, if
we fail to allocate the ret_stack, and then fail the fork, the
code will free the parent ret_stack. This is because the child
duplicated the parent and currently points to the parent's ret_stack.
This patch always initializes the task's ret_stack to NULL.
[ Impact: prevent crash of parent on low memory during fork ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The code that handles the tasks ret_stack allocation for every task
assumes that only an interrupt can cause issues (even though interrupts
are disabled).
In reality, the code is allocating the ret_stack for tasks that may be
running on other CPUs and there are not efficient memory barriers to
handle this case.
[ Impact: prevent crash due to using of uninitialized ret_stack variables ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The function graph tracer checks if the task_struct has ret_stack defined
to know if it is OK or not to use it. The initialization is done for
all tasks by one process, but the idle tasks use the same initialization
used by new tasks.
If an interrupt happens on an idle task that just had the ret_stack
created, but before the rest of the initialization took place, then
we can corrupt the return address of the functions.
This patch moves the setting of the task_struct's ret_stack to after
the other variables have been initialized.
[ Impact: prevent kernel panic on idle task when starting function graph ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
When the function graph tracer is enabled, it calls the initialization
needed for the init tasks that would be called on all created tasks.
The problem is that this is called every time the function graph tracer
is enabled, and the ret_stack is allocated for the idle tasks each time.
Thus, the old ret_stack is lost and a memory leak is created.
This is also dangerous because if an interrupt happened on another CPU
with the init task and the ret_stack is replaced, we then lose all the
return pointers for the interrupt, and a crash would take place.
[ Impact: fix memory leak and possible crash due to race ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
A race was found that if one were to enable and disable the function
profiler repeatedly, then the system can panic. This was because a profiled
function may be preempted just before disabling interrupts. While
the profiler is disabled and then reenabled, the preempted function
could start again, and access the hash as it is being initialized.
This just adds a check in the irq disabled part to check if the profiler
is enabled, and if it is not then it will just exit.
When the system is disabled, the profile_enabled variable is cleared
before calling the unregistering of the function profiler. This
unregistering calls stop machine which also acts as a synchronize schedule.
[ Impact: fix panic in enabling/disabling function profiler ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The trace_pipe did not recognize the latency format flag and would produce
different output than the trace file. The problem was partly due that
the trace flags in the iterator was not set as well as the trace_pipe
zeros out part of the iterator (including the flags) to be able to use
the same routines as the trace file. trace_flags of the iterator should
not cause any problems when not zeroed out by for trace_pipe.
Reported-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
A patch to allow the use of __print_symbolic and __print_flags
from a module. This allows the current GFS2 tracing patch to
build.
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
LKML-Reference: <1243868015.29604.542.camel@localhost.localdomain>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
__string() is limited:
- it's a char array, but we may want to define array with other types
- a source string should be available, but we may just know the string size
We introduce __dynamic_array() to break those limitations, and __string()
becomes a wrapper of it. As a side effect, now __get_str() can be used
in TP_fast_assign but not only TP_print.
Take XFS for example, we have the string length in the dirent, but the
string itself is not NULL-terminated, so __dynamic_array() can be used:
TRACE_EVENT(xfs_dir2,
TP_PROTO(struct xfs_da_args *args),
TP_ARGS(args),
TP_STRUCT__entry(
__field(int, namelen)
__dynamic_array(char, name, args->namelen + 1)
...
),
TP_fast_assign(
char *name = __get_str(name);
if (args->namelen)
memcpy(name, args->name, args->namelen);
name[args->namelen] = '\0';
__entry->namelen = args->namelen;
),
TP_printk("name %.*s namelen %d",
__entry->namelen ? __get_str(name) : NULL
__entry->namelen)
);
[ Impact: allow defining dynamic size arrays ]
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <4A2384D2.3080403@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Both event tracer and sched switch plugin are selected by default
by all generic tracers. But if no generic tracer is enabled, their options
appear. But ether one of them will select the other, thus it only
makes sense to have the default tracers be selected by one option.
[ Impact: clean up kconfig menu ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
There are two options that are selected by all tracers, but we want
to have those options available when no tracer is selected. These are
The event tracer and sched switch tracer.
The are enabled by all tracers, but if a tracer is not selected we want
the options to appear. All tracers including them select TRACING.
Thus what we would like to do is:
config EVENT_TRACER
bool "prompt"
depends on TRACING
select TRACING
But that gives us a bug in the kbuild system since we just created a
circular dependency. We only want the prompt to show when TRACING is off.
This patch adds GENERIC_TRACER that all tracers will select instead of
TRACING. The two options (sched switch and event tracer) will select
TRACING directly and depend on !GENERIC_TRACER. This solves the cicular
dependency.
[ Impact: hide options that are selected by default ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
When using ftrace=function on the command line to trace functions
on boot up, one can not filter out functions that are commonly called.
This patch adds two new ftrace command line commands.
ftrace_notrace=function-list
ftrace_filter=function-list
Where function-list is a comma separated list of functions to filter.
The ftrace_notrace will make the functions listed not be included
in the function tracing, and ftrace_filter will only trace the functions
listed.
These two act the same as the debugfs/tracing/set_ftrace_notrace and
debugfs/tracing/set_ftrace_filter respectively.
The simple glob expressions that are allowed by the filter files can also
be used by the command line interface.
ftrace_notrace=rcu*,*lock,*spin*
Will not trace any function that starts with rcu, ends with lock, or has
the word spin in it.
Note, if the self tests are enabled, they may interfere with the filtering
set by the command lines.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
register_stat_tracer() uses list_for_each_entry_safe
to check whether a tracer is already present in the list.
But we don't delete anything from the list here, so
we don't need the safe version
[ Impact: cleanup list use is stat tracing ]
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
- remove duplicate code in stat_seq_init()
- update comments to reflect the change from stat list to stat rbtree
[ Impact: clean up ]
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
When closing a trace_stat file, we destroy the rbtree constructed during
file open, but there is memory leak that the root node is not freed.
[ Impact: fix memory leak when closing a trace_stat file ]
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Currently the output of trace_stat/workqueues is totally reversed:
# cat /debug/tracing/trace_stat/workqueues
...
1 17 17 210 37 `-blk_unplug_work+0x0/0x57
1 3779 3779 181 11 |-cfq_kick_queue+0x0/0x2f
1 3796 3796 kblockd/1:120
...
The correct output should be:
1 3796 3796 kblockd/1:120
1 3779 3779 181 11 |-cfq_kick_queue+0x0/0x2f
1 17 17 210 37 `-blk_unplug_work+0x0/0x57
It's caused by "tracing/stat: replace linked list by an rbtree for
sorting"
(53059c9b67a62a3dc8c80204d3da42b9267ea5a0).
dummpy_cmp() should return -1, so rb_node will always be inserted as
right-most node in the rbtree, thus we sort the output in ascending
order.
[ Impact: fix the output of trace_stat/workqueues ]
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
When the stat tracing framework prepares the entries from a tracer
to output them to the user, it starts by computing a linear sort
through a linked list to give the entries ordered by relevance
to the user.
This is quite ugly and causes a small latency when we begin to
read the file.
This patch changes that by turning the linked list into a red-black
tree. Athough the whole iteration using the start and next tracer
callbacks while opening the file remain the same, it is now much
more fast and scalable.
The rbtree guarantees O(log(n)) insertions whereas a linked
list with linear sorting brought us a O(n) despair. Now the
(visible) latency has disapeared.
[ Impact: kill the latency while starting to read a stat tracer file ]
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
The "trace" prefix in struct trace_stat_session type is annoying while
reading the trace_stat.c file. It makes the lines longer, and
is not that much useful to explain the sense of this type.
Just keep "struct stat_session" for this type.
[ Impact: make the code a bit more readable ]
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
The blankline between each cpu's workqueue stat is not necessary, because
the cpu number is enough to part them by eye.
Old style also caused a blankline below headline, and made code complex
by using lock, disableirq and get cpu var.
Old style:
# CPU INSERTED EXECUTED NAME
# | | | |
0 8644 8644 events/0
0 0 0 cpuset
...
0 1 1 kdmflush
1 35365 35365 events/1
...
New style:
# CPU INSERTED EXECUTED NAME
# | | | |
0 8644 8644 events/0
0 0 0 cpuset
...
0 1 1 kdmflush
1 35365 35365 events/1
...
[ Impact: provide more readable code ]
Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tom Zanussi <tzanussi@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
cpu_workqueue_stats->first_entry is useless because we can retrieve the
header of a cpu workqueue using:
if (&cpu_workqueue_stats->list == workqueue_cpu_stat(cpu)->list.next)
[ Impact: cleanup ]
Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tom Zanussi <tzanussi@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
No need to use list_for_each_entry_safe() in iteration without deleting
any node, we can use list_for_each_entry() instead.
[ Impact: cleanup ]
Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tom Zanussi <tzanussi@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
v3: zhaolei@cn.fujitsu.com: Change TRACE_EVENT definition to new format
introduced by Steven Rostedt: consolidate trace and trace_event headers
v2: kosaki@jp.fujitsu.com: print the function names instead of addr, and zap
the work addr
v1: zhaolei@cn.fujitsu.com: Make workqueue tracepoints use TRACE_EVENT macro
TRACE_EVENT is a more generic way to define tracepoints.
Doing so adds these new capabilities to the tracepoints:
- zero-copy and per-cpu splice() tracing
- binary tracing without printf overhead
- structured logging records exposed under /debug/tracing/events
- trace events embedded in function tracer output and other plugins
- user-defined, per tracepoint filter expressions
Then, this patch converts DEFINE_TRACE to TRACE_EVENT in workqueue related
tracepoints.
[ Impact: expand workqueue tracer to events tracing ]
Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tom Zanussi <tzanussi@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
This patch adds __print_symbolic which is similar to __print_flags but
works for an enumeration type instead. That is, there is only a one to one
mapping between the values and the symbols. When a match is made, then
it is printed, otherwise the hex value is outputed.
[ Impact: add interface for showing symbol names in events ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Developers have been asking for the ability in the ftrace event tracer
to display names of bits in a flags variable.
Instead of printing out c2, it would be easier to read FOO|BAR|GOO,
assuming that FOO is bit 1, BAR is bit 6 and GOO is bit 7.
Some examples where this would be useful are the state flags in a context
switch, kmalloc flags, and even permision flags in accessing files.
[
v2 changes include:
Frederic Weisbecker's idea of using a mask instead of bits,
thus we can output GFP_KERNEL instead of GPF_WAIT|GFP_IO|GFP_FS.
Li Zefan's idea of allowing the caller of __print_flags to add their
own delimiter (or no delimiter) where we can get for file permissions
rwx instead of r|w|x.
]
[
v3 changes:
Christoph Hellwig's idea of using an array instead of va_args.
]
[ Impact: better displaying of flags in trace output ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Always use ftrace_event_enable_disable() to enable/disable an event
so that we can factorize out the event toggling code.
[ Impact: factorize and cleanup event tracing code ]
Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tom Zanussi <tzanussi@gmail.com>
LKML-Reference: <4A14FDFE.2080402@cn.fujitsu.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
I found that there is nothing to protect event_hash in
ftrace_find_event(). Rcu protects the event hashlist
but not the event itself while we use it after its extraction
through ftrace_find_event().
This lack of a proper locking in this spot opens a race
window between any event dereferencing and module removal.
Eg:
--Task A--
print_trace_line(trace) {
event = find_ftrace_event(trace)
--Task B--
trace_module_remove_events(mod) {
list_trace_events_module(ev, mod) {
unregister_ftrace_event(ev->event) {
hlist_del(ev->event->node)
list_del(....)
}
}
}
|--> module removed, the event has been dropped
--Task A--
event->print(trace); // Dereferencing freed memory
If the event retrieved belongs to a module and this module
is concurrently removed, we may end up dereferencing a data
from a freed module.
RCU could solve this, but it would add latency to the kernel and
forbid tracers output callbacks to call any sleepable code.
So this fix converts 'trace_event_mutex' to a read/write semaphore,
and adds trace_event_read_lock() to protect ftrace_find_event().
[ Impact: fix possible freed memory dereference in ftrace ]
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <4A114806.7090302@cn.fujitsu.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
register_module_notifier() returns zero in the success case.
So fix the inverted fail case check in trace events modules
handler.
[ Impact: fix spurious warning on ftrace initialization]
Reported-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
debugfs directory entries for devices are not removed on some
of the failure pathes in do_blk_trace_setup().
One way to reproduce is to start blktrace on multiple devices
with insufficient Vmalloc space: Devices will fail with
a message like this:
BLKTRACESETUP(2) /dev/sdu failed: 5/Input/output error
If so, the respective entries in debugfs
(e.g. /sys/kernel/debug/block/sdu) will remain and subsequent
attempts to start blktrace on the respective devices will not
succeed due to existing directories.
[ Impact: fix /debug/tracing file cleanup corner case ]
Signed-off-by: Stefan Raspl <stefan.raspl@linux.vnet.ibm.com>
Acked-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: schwidefsky@de.ibm.com
Cc: heiko.carstens@de.ibm.com
LKML-Reference: <4A1266CC.5040801@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
return zero should be correct, so fix it.
[ Impact: eliminate incorrect syslog message ]
Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: rostedt@goodmis.org
LKML-Reference: <1242545498-7285-1-git-send-email-tom.leiming@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
We should leave the last slot for the ending '\0'.
[ Impact: fix possible crash when the length of an operand is 128 ]
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <4A0CDC8C.30602@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
[ Impact: fix deadlock in a rare case we fail to allocate memory ]
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <4A0CDC6F.7070200@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The stack tracer stores eight entries in the ring buffer when an event
traces the stack. The output outputs all eight entries regardless of
how many entries were recorded.
This patch breaks out of the loop when a null entry is discovered.
[ Impact: only print the stack that is recorded ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
* Arun R Bharadwaj <arun@linux.vnet.ibm.com> [2009-04-16 12:11:36]:
The following pinned hrtimers have been identified and marked:
1)sched_rt_period_timer
2)tick_sched_timer
3)stack_trace_timer_fn
[ tglx: fixup the hrtimer pinned mode ]
Signed-off-by: Arun R Bharadwaj <arun@linux.vnet.ibm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This is a bit of micro-optimizations. But since the ring buffer is used
in tracing every function call, it is an extreme hot path. Every nanosecond
counts.
This change shows over 5% improvement in the ring-buffer-benchmark.
[ Impact: more efficient code ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The ring_buffer_time_stamp that is exported adds a little more overhead
than is needed for using it internally. This patch adds an internal
timestamp function that can be inlined (a single line function)
and used internally for the ring buffer.
[ Impact: a little less overhead to the ring buffer ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Doing some small changes in the fast path of the ring buffer recording
saves over 3% in the ring-buffer-benchmark test.
[ Impact: a little faster ring buffer recording ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The event length is calculated and passed in to rb_reserve_next_event
in two different locations. Having rb_reserve_next_event do the
calculations directly makes only one location to do the change and
causes the calculation to be inlined by gcc.
Before:
text data bss dec hex filename
16538 24 12 16574 40be kernel/trace/ring_buffer.o
After:
text data bss dec hex filename
16490 24 12 16526 408e kernel/trace/ring_buffer.o
[ Impact: smaller more efficient code ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The rb_reserve_next_event is only called for the data type (type = 0).
There is no reason to pass in the type to the function.
Before:
text data bss dec hex filename
16554 24 12 16590 40ce kernel/trace/ring_buffer.o
After:
text data bss dec hex filename
16538 24 12 16574 40be kernel/trace/ring_buffer.o
[ Impact: cleaner, smaller and slightly more efficient code ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Although we check if "missed" is not zero, we divide by hit + missed,
and the addition can possible overflow and become a divide by zero.
This patch checks for this case, and will report it when it happens
then modify "hit" to make the calculation be non zero.
[ Impact: prevent possible divide by zero in ring-buffer-benchmark ]
Reported-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The use of numeric constants is discouraged. It is cleaner and more
descriptive to use macros for constant time conversions.
This patch also removes an extra new line.
[ Impact: more descriptive time conversions ]
Reported-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
struct request has had a few different ways to represent some
properties of a request. ->hard_* represent block layer's view of the
request progress (completion cursor) and the ones without the prefix
are supposed to represent the issue cursor and allowed to be updated
as necessary by the low level drivers. The thing is that as block
layer supports partial completion, the two cursors really aren't
necessary and only cause confusion. In addition, manual management of
request detail from low level drivers is cumbersome and error-prone at
the very least.
Another interesting duplicate fields are rq->[hard_]nr_sectors and
rq->{hard_cur|current}_nr_sectors against rq->data_len and
rq->bio->bi_size. This is more convoluted than the hard_ case.
rq->[hard_]nr_sectors are initialized for requests with bio but
blk_rq_bytes() uses it only for !pc requests. rq->data_len is
initialized for all request but blk_rq_bytes() uses it only for pc
requests. This causes good amount of confusion throughout block layer
and its drivers and determining the request length has been a bit of
black magic which may or may not work depending on circumstances and
what the specific LLD is actually doing.
rq->{hard_cur|current}_nr_sectors represent the number of sectors in
the contiguous data area at the front. This is mainly used by drivers
which transfers data by walking request segment-by-segment. This
value always equals rq->bio->bi_size >> 9. However, data length for
pc requests may not be multiple of 512 bytes and using this field
becomes a bit confusing.
In general, having multiple fields to represent the same property
leads only to confusion and subtle bugs. With recent block low level
driver cleanups, no driver is accessing or manipulating these
duplicate fields directly. Drop all the duplicates. Now rq->sector
means the current sector, rq->data_len the current total length and
rq->bio->bi_size the current segment length. Everything else is
defined in terms of these three and available only through accessors.
* blk_recalc_rq_sectors() is collapsed into blk_update_request() and
now handles pc and fs requests equally other than rq->sector update.
This means that now pc requests can use partial completion too (no
in-kernel user yet tho).
* bio_cur_sectors() is replaced with bio_cur_bytes() as block layer
now uses byte count as the primary data length.
* blk_rq_pos() is now guranteed to be always correct. In-block users
converted.
* blk_rq_bytes() is now guaranteed to be always valid as is
blk_rq_sectors(). In-block users converted.
* blk_rq_sectors() is now guaranteed to equal blk_rq_bytes() >> 9.
More convenient one is used.
* blk_rq_bytes() and blk_rq_cur_bytes() are now inlined and take const
pointer to request.
[ Impact: API cleanup, single way to represent one property of a request ]
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Boaz Harrosh <bharrosh@panasas.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Implement accessors - blk_rq_pos(), blk_rq_sectors() and
blk_rq_cur_sectors() which return rq->hard_sector, rq->hard_nr_sectors
and rq->hard_cur_sectors respectively and convert direct references of
the said fields to the accessors.
This is in preparation of request data length handling cleanup.
Geert : suggested adding const to struct request * parameter to accessors
Sergei : spotted error in patch description
[ Impact: cleanup ]
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Geert Uytterhoeven <Geert.Uytterhoeven@sonycom.com>
Acked-by: Stephen Rothwell <sfr@canb.auug.org.au>
Tested-by: Grant Likely <grant.likely@secretlab.ca>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Ackec-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Cc: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Cc: Borislav Petkov <petkovbb@googlemail.com>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Other parts of the kernel may need to be able to enable or disable
specific events. Especially parts that create trace events.
[ Impact: allow enabling of trace events by those that create the event ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Commit 8f31bfe538
tracing/events: clean up for ftrace_set_clr_event()
Moved out the code for ftrace_set_clr_event into a helper funciton but
did not initialize the return value. As a result, we do not warn about
a typo in the echoing of events in set_event.
This patch restores the old warning:
# echo foobar > set_event
-bash: echo: write error: Invalid argument
[ Impact: restore warning of invalid entries to set_event ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
A smarter way to figure out the output of an enable file.
[ Impact: clean up ]
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4A0399A5.2080603@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Add a helper function __ftrace_set_clr_event(), and replace some
ftrace_set_clr_event() calls with this helper, thus we don't need any
kstrdup() or kmalloc().
As a side effect, this patch fixes an issue in self tests code, which is
similar to the one fixed in commit d6bf81ef0f
("tracing: append ":*" to internal setting of system events")
It's a small issue and won't cause any bug in fact, but we should do things
right anyway.
[ Impact: prevent spurious event-enabling in tracing self-tests ]
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4A03998E.3020503@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
There's a WARN_ON in the ring buffer code that makes sure preemption
is disabled. It checks "!preempt_count()". But when CONFIG_PREEMPT is not
enabled, preempt_count() is always zero, and this will trigger the warning.
[ Impact: prevent false warning on non preemptible kernels ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
It is nice to see the overhead of the benchmark test when tracing is
disabled. That is, we turn off the ring buffer just to see what the
cost of running the loop that calls into the ring buffer is.
Currently, if no entries wer made, we get 0. This is not informative.
This patch changes it to check if we had any "missed" (non recorded)
events. If so, a total count is also reported.
[ Impact: evaluate the over head of the ring buffer benchmark test ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Calling cond_resched at every iteration of the loop adds a bit of
overhead to the benchmark.
This patch does two things.
1) only calls cond-resched when CONFIG_PREEMPT is not enabled
2) only calls cond-resched after so many traces has been performed.
[ Impact: less overhead to the ring-buffer-benchmark ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Tracing can be very helpful to debug the kernel. When DEBUG_KERNEL is
enabled it is nice to enable the trace menu as well.
This patch only make the tracing menu enabled by default, it does not
make any of the tracers enabled. And the menu is only enabled by
default if DEBUG_KERNEL is enabled.
[ Impact: show tracing options to those debugging the kernel ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The system enabling of events uses the same code as the set_event file.
It passes in the name of the system to the parser and that will enable
all the events that has that system as a name.
The problem is that it will also enable events with the same name as the
system.
If you have system name foo, and system name bar, but within the system
bar, there exists an event called foo. By setting the system name foo,
you will also be enabling the event foo in the system bar. This is not
an expected result.
The solution is to pass in "foo:*", which will only enable the system
foo and not events called foo.
[ Impact: prevent accidental enabling of events with same name as a system ]
Reported-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Ingo Molnar thought that the code to calculate the time in cond_resched
is a bit too ugly and is not needed. This patch removes it and replaces
it with a simple call to cond_resched. I kept the comment that explains
the reason for the cond_resched.
[ Impact: remove ugly code ]
Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Merge reason: this topic is ready for upstream now. It passed
Oleg's review and Andrew had no further mm/*
objections/observations either.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Merge reason: tracing/core was on a .30-rc1 base and was missing out on
on a handful of tracing fixes present in .30-rc5-almost.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
In filter_add_subsystem_pred() we should release event_mutex before
calling filter_free_subsystem_preds(), since both functions hold
event_mutex.
[ Impact: fix deadlock when writing invalid pred into subsystem filter ]
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: tzanussi@gmail.com
Cc: a.p.zijlstra@chello.nl
Cc: fweisbec@gmail.com
Cc: rostedt@goodmis.org
LKML-Reference: <4A028993.7020509@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
When we set a filter for an event, such as:
echo "name == my_lock_name" > \
/debug/tracing/events/lockdep/lock_acquired/filter
then the following order of token type is parsed:
- space
- operator
- parentheses
- operand
Because the operators and parentheses have a higher precedence
than the operand characters, which is normal, then we can't
use any string containing such special characters:
()=<>!&|
To get this support and also avoid ambiguous intepretation from
the parser or the human, we can do it using double quotes so that
we keep the usual languages habits.
Then after this patch you can still declare string condition like
before:
echo name == myname
But if you want to compare against a string containing an operator
character, you can use double quotes:
echo 'name == "&myname"'
Don't forget to include the whole expression into single quotes or
the double ones will be eaten by echo.
[ Impact: support strings with special characters for tracing filters ]
Cc: Tom Zanussi <tzanussi@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Zhaolei <zhaolei@cn.fujitsu.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Currently the filtering infrastructure supports well the
numeric types and fixed sized array types.
But the recently added __string() field uses a specific
indirect offset mechanism which requires a specific
predicate. Until now it wasn't supported.
This patch adds this support and implies very few changes,
only a new predicate is needed, the management of this specific
field can be done through the usual string helpers in the
filtering infrastructure.
[ Impact: support all kinds of strings in the tracing filters ]
Cc: Tom Zanussi <tzanussi@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Zhaolei <zhaolei@cn.fujitsu.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
With the current event directory, you can only enable individual events.
The file debugfs/tracing/set_event is used to be able to enable or
disable several events at once. But that can still be awkward.
This patch adds hierarchical enabling of events. That is, each directory
in debugfs/tracing/events has an "enable" file. This file can enable
or disable all events within the directory and below.
# echo 1 > /debugfs/tracing/events/enable
will enable all events.
# echo 1 > /debugfs/tracing/events/sched/enable
will enable all events in the sched subsystem.
# echo 1 > /debugfs/tracing/events/enable
# echo 0 > /debugfs/tracing/events/irq/enable
will enable all events, but then disable just the irq subsystem events.
When reading one of these enable files, there are four results:
0 - all events this file affects are disabled
1 - all events this file affects are enabled
X - there is a mixture of events enabled and disabled
? - this file does not affect any event
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Li Zefan found that there's a race using the event ids of events and
modules. When a module is loaded, an event id is incremented. We only
have 16 bits for event ids (65536) and there is a possible (but highly
unlikely) race that we could load and unload a module that registers
events so many times that the event id counter overflows.
When it overflows, it then restarts and goes looking for available
ids. An id is available if it was added by a module and released.
The race is if you have one module add an id, and then is removed.
Another module loaded can use that same event id. But if the old module
still had events in the ring buffer, the new module's call back would
get bogus data. At best (and most likely) the output would just be
garbage. But if the module for some reason used pointers (not recommended)
then this could potentially crash.
The safest thing to do is just reset the ring buffer if a module that
registered events is removed.
[ Impact: prevent unpredictable results of event id overflows ]
Reported-by: Li Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <49FEAFD0.30106@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The ring buffer benchmark/test runs a producer for 10 seconds.
This is done with preemption and interrupts enabled. But if the kernel
is not compiled with CONFIG_PREEMPT, it basically stops everything
but interrupts for 10 seconds.
Although this is just a test and is not for production, this attribute
can be quite annoying. It can also spawn badness elsewhere.
This patch solves the issues by calling "cond_resched" when the system
is not compiled with CONFIG_PREEMPT. It also keeps track of the time
spent to call cond_resched such that it does not go against the
time calculations. That is, if the task schedules away, the time scheduled
out is removed from the test data. Note, this only works for non PREEMPT
because we do not know when the task is scheduled out if we have PREEMPT
enabled.
[ Impact: prevent test from stopping the world for 10 seconds ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Ingo Molnar thought the code would be cleaner if we used a function call
instead of a goto for moving the tail page. After implementing this,
it seems that gcc still inlines the result and the output is pretty much
the same. Since this is considered a cleaner approach, might as well
implement it.
[ Impact: code clean up ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The result of the allocation of the ring buffer read page in the
ring buffer bench mark does not check the return to see if a page
was actually allocated. This patch fixes that.
[ Impact: avoid NULL dereference ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The code in __rb_reserve_next checks on page overflow if it is the
original commiter and then resets the page back to the original
setting. Although this is fine, and the code is correct, it is
a bit fragil. Some experimental work I did breaks it easily.
The better and more robust solution is to have all commiters that
overflow the page, simply subtract what they added.
[ Impact: more robust ring buffer account management ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This compiler warning:
CC kernel/trace/trace_output.o
kernel/trace/trace_output.c: In function ‘register_ftrace_event’:
kernel/trace/trace_output.c:544: warning: ‘list’ may be used uninitialized in this function
Is wrong as 'list' is always initialized - but GCC (4.3.2) does not
recognize this relationship properly.
Work around the warning by initializing the variable to NULL.
[ Impact: fix false positive compiler warning ]
Signed-off-by: Jaswinder Singh Rajput <jaswinderrajput@gmail.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This attempts to clarify names utilized during block I/O remap
operations (partition, volume manager). It correctly matches up the
/from/ information for both device & sector. This takes in the concept
from Kosaki Motohiro and extends it to include better naming for the
"device_from" field.
[ Impact: cleanup ]
Signed-off-by: Alan D. Brunelle <alan.brunelle@hp.com>
Reviewed-by: Li Zefan <lizf@cn.fujitsu.com>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
LKML-Reference: <49FF4FAE.3000301@hp.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
A module will add/remove its trace events when it gets loaded/unloaded, so
the ftrace_events list is not "const", and concurrent access needs to be
protected.
This patch thus fixes races between loading/unloding modules and read
'available_events' or read/write 'set_event', etc.
Below shows how to reproduce the race:
# for ((; ;)) { cat /mnt/tracing/available_events; } > /dev/null &
# for ((; ;)) { insmod trace-events-sample.ko; rmmod sample; } &
After a while:
BUG: unable to handle kernel paging request at 0010011c
IP: [<c1080f27>] t_next+0x1b/0x2d
...
Call Trace:
[<c10c90e6>] ? seq_read+0x217/0x30d
[<c10c8ecf>] ? seq_read+0x0/0x30d
[<c10b4c19>] ? vfs_read+0x8f/0x136
[<c10b4fc3>] ? sys_read+0x40/0x65
[<c1002a68>] ? sysenter_do_call+0x12/0x36
[ Impact: fix races when concurrent accessing ftrace_events list ]
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Tom Zanussi <tzanussi@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <4A00F709.3080800@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
When unloading a module, memory allocated by init_preds() and
trace_define_field() is not freed.
[ Impact: fix memory leak ]
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Tom Zanussi <tzanussi@gmail.com>
LKML-Reference: <4A00F6E0.3040503@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This patch adds code that can benchmark the ring buffer as well as
test it. This code can be compiled into the kernel (not recommended)
or as a module.
A separate ring buffer is used to not interfer with other users, like
ftrace. It creates a producer and a consumer (option to disable creation
of the consumer) and will run for 10 seconds, then sleep for 10 seconds
and then repeat.
While running, the producer will write 10 byte loads into the ring
buffer with just putting in the current CPU number. The reader will
continually try to read the buffer. The reader will alternate from reading
the buffer via event by event, or by full pages.
The output is a pr_info, thus it will fill up the syslogs.
Starting ring buffer hammer
End ring buffer hammer
Time: 9000349 (usecs)
Overruns: 12578640
Read: 5358440 (by events)
Entries: 0
Total: 17937080
Missed: 0
Hit: 17937080
Entries per millisec: 1993
501 ns per entry
Sleeping for 10 secs
Starting ring buffer hammer
End ring buffer hammer
Time: 9936350 (usecs)
Overruns: 0
Read: 28146644 (by pages)
Entries: 74
Total: 28146718
Missed: 0
Hit: 28146718
Entries per millisec: 2832
353 ns per entry
Sleeping for 10 secs
Time: is the time the test ran
Overruns: the number of events that were overwritten and not read
Read: the number of events read (either by pages or events)
Entries: the number of entries left in the buffer
(the by pages will only read full pages)
Total: Entries + Read + Overruns
Missed: the number of entries that failed to write
Hit: the number of entries that were written
The above example shows that it takes ~353 nanosecs per entry when
there is a reader, reading by pages (and no overruns)
The event by event reader slowed the producer down to 501 nanosecs.
[ Impact: see how changes to the ring buffer affect stability and performance ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
In the hot path of the ring buffer "__rb_reserve_next" there's a big
if statement that does not even return back to the work flow.
code;
if (cross to next page) {
[ lots of code ]
return;
}
more code;
The condition is even the unlikely path, although we do not denote it
with an unlikely because gcc is fine with it. The condition is true when
the write crosses a page boundary, and we need to start at a new page.
Having this if statement makes it hard to read, but calling another
function to do the work is also not appropriate, because we are using a lot
of variables that were set before the if statement, and we do not want to
send them as parameters.
This patch changes it to a goto:
code;
if (cross to next page)
goto next_page;
more code;
return;
next_page:
[ lots of code]
This makes the code easier to understand, and a bit more obvious.
The output from gcc is practically identical. For some reason, gcc decided
to use different registers when I switched it to a goto. But other than that,
the logic is the same.
[ Impact: easier to read code ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
When adding the EXPORT_SYMBOL to some of the tracing API, I accidently
used EXPORT_SYMBOL instead of EXPORT_SYMBOL_GPL. This patch fixes
that mistake.
[ Impact: export the tracing code only for GPL modules ]
Reported-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
As a precaution, it is best to disable writing to the ring buffers
when reseting them.
[ Impact: prevent weird things if write happens during reset ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
In the swap page ring buffer code that is used by the ftrace splice code,
we scan the page to increment the counter of entries read.
With the number of entries already in the page we simply need to add it.
[ Impact: speed up reading page from ring buffer ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Currently, when the ring buffer writer overflows the buffer and must
write over non consumed data, we increment the overrun counter by
reading the entries on the page we are about to overwrite. This reads
the entries one by one.
This is not very effecient. This patch adds another entry counter
into each buffer page descriptor that keeps track of the number of
entries on the page. Now on overwrite, the overrun counter simply
needs to add the number of entries that is on the page it is about
to overwrite.
[ Impact: speed up of ring buffer in overwrite mode ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The entries counter in cpu buffer is not atomic. It can be updated by
other interrupts or from another CPU (readers).
But making entries into "atomic_t" causes an atomic operation that can
hurt performance. Instead we convert it to a local_t that will increment
a counter with a local CPU atomic operation (if the arch supports it).
Instead of fighting with readers and overwrites that decrement the counter,
I added a "read" counter. Every time a reader reads an entry it is
incremented.
We already have a overrun counter and with that, the entries counter and
the read counter, we can calculate the total number of entries in the
buffer with:
(entries - overrun) - read
As long as the total number of entries in the ring buffer is less than
the word size, this will work. But since the entries counter was previously
a long, this is no different than what we had before.
Thanks to Andrew Morton for pointing out in the first version that
atomic_t does not replace unsigned long. I switched to atomic_long_t
even though it is signed. A negative count is most likely a bug.
[ Impact: keep accurate count of cpu buffer entries ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This patch adds stats to the ftrace ring buffers:
# cat /debugfs/tracing/per_cpu/cpu0/stats
entries: 42360
overrun: 30509326
commit overrun: 0
nmi dropped: 0
Where entries are the total number of data entries in the buffer.
overrun is the number of entries not consumed and were overwritten by
the writer.
commit overrun is the number of entries dropped due to nested writers
wrapping the buffer before the initial writer finished the commit.
nmi dropped is the number of entries dropped due to the ring buffer
lock being held when an nmi was going to write to the ring buffer.
Note, this field will be meaningless and will go away when the ring
buffer becomes lockless.
[ Impact: let userspace know what is happening in the ring buffers ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The WARN_ON in the ring buffer when a commit is preempted and the
buffer is filled by preceding writes can happen in normal operations.
The WARN_ON makes it look like a bug, not to mention, because
it does not stop tracing and calls printk which can also recurse, this
is prone to deadlock (the WARN_ON is not in a position to recurse).
This patch removes the WARN_ON and replaces it with a counter that
can be retrieved by a tracer. This counter is called commit_overrun.
While at it, I added a nmi_dropped counter to count any time an NMI entry
is dropped because the NMI could not take the spinlock.
[ Impact: prevent deadlock by printing normal case warning ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
I'm adding a module to do a series of tests on the ring buffer as well
as benchmarks. This module needs to have more of the ring buffer API
exported. There's nothing wrong with reading the ring buffer from a
module.
[ Impact: allow modules to read pages from the ring buffer ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Replace the current event parser hack with a better one. Filters are
no longer specified predicate by predicate, but all at once and can
use parens and any of the following operators:
numeric fields:
==, !=, <, <=, >, >=
string fields:
==, !=
predicates can be combined with the logical operators:
&&, ||
examples:
"common_preempt_count > 4" > filter
"((sig >= 10 && sig < 15) || sig == 17) && comm != bash" > filter
If there was an error, the erroneous string along with an error
message can be seen by looking at the filter e.g.:
((sig >= 10 && sig < 15) || dsig == 17) && comm != bash
^
parse_error: Field not found
Currently the caret for an error always appears at the beginning of
the filter; a real position should be used, but the error message
should be useful even without it.
To clear a filter, '0' can be written to the filter file.
Filters can also be set or cleared for a complete subsystem by writing
the same filter as would be written to an individual event to the
filter file at the root of the subsytem. Note however, that if any
event in the subsystem lacks a field specified in the filter being
set, the set will fail and all filters in the subsytem are
automatically cleared. This change from the previous version was made
because using only the fields that happen to exist for a given event
would most likely result in a meaningless filter.
Because the logical operators are now implemented as predicates, the
maximum number of predicates in a filter was increased from 8 to 16.
[ Impact: add new, extended trace-filter implementation ]
Signed-off-by: Tom Zanussi <tzanussi@gmail.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: fweisbec@gmail.com
Cc: Li Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <1240905899.6416.121.camel@tropicana>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
The new filter comparison ops need to be able to distinguish between
signed and unsigned field types, so add an is_signed flag/param to the
event field struct/trace_define_fields(). Also define a simple macro,
is_signed_type() to determine the signedness at compile time, used in the
trace macros. If the is_signed_type() macro won't work with a specific
type, a new slightly modified version of TRACE_FIELD() called
TRACE_FIELD_SIGN(), allows the signedness to be set explicitly.
[ Impact: extend trace-filter code for new feature ]
Signed-off-by: Tom Zanussi <tzanussi@gmail.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: fweisbec@gmail.com
Cc: Li Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <1240905893.6416.120.camel@tropicana>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Create a new event_filter object, and move the pred-related members
out of the call and subsystem objects and into the filter object - the
details of the filter implementation don't need to be exposed in the
call and subsystem in any case, and it will also help make the new
parser implementation a little cleaner.
[ Impact: refactor trace-filter code to prepare for new features ]
Signed-off-by: Tom Zanussi <tzanussi@gmail.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: fweisbec@gmail.com
Cc: Li Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <1240905887.6416.119.camel@tropicana>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
The pages allocated for the splice binary buffer did not initialize
the ref count correctly. This caused pages not to be freed and causes
a drastic memory leak.
Thanks to logdev I was able to trace the tracer to find where the leak
was.
[ Impact: stop memory leak when using splice ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
The warning output in trace_recursive_lock uses %d for a long when
it should be %ld.
[ Impact: fix compile warning ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Splice works with pages, it is much more effecient to use an entire
page than to copy bits over several pages.
Using logdev to trace the internals of the splice mechanism, I was
able to see that splice can be very aggressive. When tracing is
occurring, and the reader caught up to the writer, and the writer
is on the reader page, the reader will copy what is there into the
splice page. Splice may iterate over several pages and if the
writer is still writing to the page, the reader will keep copying
bits to new pages to pass to userspace.
This patch changes it to only pass data to userspace if the page
is full (the writer has left the page). This has a small side effect
that splice can not read a partial page, and must wait for the
page to fill. This should not be an issue. If tracing has stopped,
then a use of "read" will still read all of the page.
[ Impact: better performance for ring buffer splice code ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The splice code allocates a page even when the ring buffer is empty.
It detects the ring buffer being empty when it it fails to copy
anything from the ring buffer into the page.
This patch adds a check to see if there is anything in the ring buffer
before allocating a page.
Thanks to logdev for letting me trace the tracer to find this.
[ Impact: speed up due to removing unnecessary allocation ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The pages allocated for the splice binary buffer did not initialize
the ref count correctly. This caused pages not to be freed and causes
a drastic memory leak.
Thanks to logdev I was able to trace the tracer to find where the leak
was.
[ Impact: stop memory leak when using splice ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
ftrace_dump is used for printing out the contents of the ftrace ring buffer
to the console on failure. Currently it uses a spinlock to synchronize
the output from multiple failures on different CPUs. This spin lock
currently is a normal spinlock and can cause issues with lockdep and
lock tracing.
This patch converts it to raw since it is for error handling only.
The lock is local to the ftrace_dump and is not used by any other
infrastructure.
[ Impact: prevent ftrace_dump from locking up by internal tracing ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
For proper module reference counting, the file_operations that modules use
must have the "owner" field set to the module. Unfortunately, the trace events
use share file_operations. The same file_operations are used by all both
kernel core and all modules.
This patch makes the modules allocate their own file_operations and
copies the functions from the core kernel. This allows those file
operations to be owned by the module.
Care is taken to free this code on module unload.
Thanks to Greg KH for reminding me that file_operations must be owned
by the module to have reference counting take place.
[ Impact: fix modular tracepoints / potential crash ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de>
With modules being able to add trace events, and the max trace event
counter is 16 bits (65536) we can overflow the counter easily
with a simple while loop adding and removing modules that contain
trace events.
This patch links together the registered trace events and on overflow
searches for available trace event ids. It will still fail if
over 65536 events are registered, but considering that a typical
kernel only has 22000 functions, 65000 events should be sufficient.
Reported-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Conflicts:
arch/x86/kernel/ptrace.c
Merge reason: fix the conflict above, and also pick up the CONFIG_BROKEN
dependency change from upstream so that we can remove it
here.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
RB_MAX_SMALL_DATA = 28bytes is too small for most tracers, it wastes
an 'u32' to save the actually length for events which data size > 28.
This fix uses compressed event header and enlarges RB_MAX_SMALL_DATA.
[ Impact: saves about 0%-12.5%(depends on tracer) memory in ring_buffer ]
Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
LKML-Reference: <49F13189.3090000@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
The events exported by TRACE_EVENT are automated and are guaranteed
to be correct when used.
The internal ftrace structures on the other hand are more manually
exported. These require the ftrace maintainer to make sure they
are up to date.
This patch adds a size check to help flag when a type changes in
an internal ftrace data structure, and the update needs to be reflected
in the export.
If a export is incorrect, then the only harm is that the user space
tools will not know how to correctly read the internal structures of
ftrace.
[ Impact: help prevent inconsistent ftrace format print outs ]
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
With the new event tracing registration, we must increase the number
of events that can be registered. Currently the type field is only
one byte, which leaves us only 256 possible events.
Since we do not save the CPU number in the tracer anymore (it is determined
by the per cpu ring buffer that is used) we have an extra byte to use.
This patch increases the size of type from 1 byte (256 events) to
2 bytes (65,536 events).
It also adds a WARN_ON_ONCE if we exceed that limit.
[ Impact: allow more than 255 events ]
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
The code had the following outside the lock:
if (next != wakeup_task)
return;
pc = preempt_count();
/* The task we are waiting for is waking up */
data = wakeup_trace->data[wakeup_cpu];
On initialization, wakeup_task is NULL and wakeup_cpu -1. This code
is not under a lock. If wakeup_task is set on another CPU as that
task is waking up, we can see the wakeup_task before wakeup_cpu is
set. If we read wakeup_cpu while it is still -1 then we will have
a bad data pointer.
This patch moves the reading of wakeup_cpu within the protection of
the spinlock used to protect the writing of wakeup_cpu and wakeup_task.
[ Impact: remove possible race causing invalid pointer dereference ]
Reported-by: Maneesh Soni <maneesh@in.ibm.com>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
struct trace_entry->type is unsigned char, while trace event's id is
int type, thus for a event with id >= 256, it's entry->type is cast
to (id % 256), and then we can't see the trace output of this event.
# insmod trace-events-sample.ko
# echo foo_bar > /mnt/tracing/set_event
# cat /debug/tracing/events/trace-events-sample/foo_bar/id
256
# cat /mnt/tracing/trace_pipe
<...>-3548 [001] 215.091142: Unknown type 0
<...>-3548 [001] 216.089207: Unknown type 0
<...>-3548 [001] 217.087271: Unknown type 0
<...>-3548 [001] 218.085332: Unknown type 0
[ Impact: fix output for trace events with id >= 256 ]
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tom Zanussi <tzanussi@gmail.com>
LKML-Reference: <49EEDB0E.5070207@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
On boot up, to save memory, ftrace allocates the minimum buffer
which is two pages. Ftrace also goes through a series of tests
(when configured) on boot up. These tests can fill up a page within
a single interrupt.
The ring buffer also has a WARN_ON when it detects that the buffer was
completely filled within a single commit (other commits are allowed to
be nested).
Combine the small buffer on start up, with the tests that can fill more
than a single page within an interrupt, this can trigger the WARN_ON.
This patch makes the WARN_ON only happen when the ring buffer consists
of more than two pages.
[ Impact: prevent false WARN_ON in ftrace startup tests ]
Reported-by: Ingo Molnar <mingo@elte.hu>
LKML-Reference: <20090421094616.GA14561@elte.hu>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Suppose we would like to trace all tasks named '123', but this
will fail:
# echo 'parent_comm == 123' > events/sched/sched_process_fork/filter
bash: echo: write error: Invalid argument
Don't guess the type of the filter pred in filter_parse(), but instead
we check it in __filter_add_pred().
[ Impact: extend allowed filter field string values ]
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Tom Zanussi <tzanussi@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <49ED8DEB.6000700@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
If writing subsys->filter returns EINVAL or ENOSPC, the original
filters in subsys/ and subsys/events/ will be removed. This is
definitely wrong.
[ Impact: fix filter setting semantics on error condition ]
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Tom Zanussi <tzanussi@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <49ED8DD2.2070700@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
