linux/kernel/cpu.c
Thomas Gleixner 757c989b99 cpu/hotplug: Make target state writeable
Make it possible to write a target state to the per cpu state file, so we can
switch between states.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: Rik van Riel <riel@redhat.com>
Cc: Rafael Wysocki <rafael.j.wysocki@intel.com>
Cc: "Srivatsa S. Bhat" <srivatsa@mit.edu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Turner <pjt@google.com>
Link: http://lkml.kernel.org/r/20160226182341.022814799@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2016-03-01 20:36:55 +01:00

1196 lines
28 KiB
C

/* CPU control.
* (C) 2001, 2002, 2003, 2004 Rusty Russell
*
* This code is licenced under the GPL.
*/
#include <linux/proc_fs.h>
#include <linux/smp.h>
#include <linux/init.h>
#include <linux/notifier.h>
#include <linux/sched.h>
#include <linux/unistd.h>
#include <linux/cpu.h>
#include <linux/oom.h>
#include <linux/rcupdate.h>
#include <linux/export.h>
#include <linux/bug.h>
#include <linux/kthread.h>
#include <linux/stop_machine.h>
#include <linux/mutex.h>
#include <linux/gfp.h>
#include <linux/suspend.h>
#include <linux/lockdep.h>
#include <linux/tick.h>
#include <linux/irq.h>
#include <trace/events/power.h>
#define CREATE_TRACE_POINTS
#include <trace/events/cpuhp.h>
#include "smpboot.h"
/**
* cpuhp_cpu_state - Per cpu hotplug state storage
* @state: The current cpu state
* @target: The target state
*/
struct cpuhp_cpu_state {
enum cpuhp_state state;
enum cpuhp_state target;
};
static DEFINE_PER_CPU(struct cpuhp_cpu_state, cpuhp_state);
/**
* cpuhp_step - Hotplug state machine step
* @name: Name of the step
* @startup: Startup function of the step
* @teardown: Teardown function of the step
* @skip_onerr: Do not invoke the functions on error rollback
* Will go away once the notifiers are gone
* @cant_stop: Bringup/teardown can't be stopped at this step
*/
struct cpuhp_step {
const char *name;
int (*startup)(unsigned int cpu);
int (*teardown)(unsigned int cpu);
bool skip_onerr;
bool cant_stop;
};
static DEFINE_MUTEX(cpuhp_state_mutex);
static struct cpuhp_step cpuhp_bp_states[];
static struct cpuhp_step cpuhp_ap_states[];
/**
* cpuhp_invoke_callback _ Invoke the callbacks for a given state
* @cpu: The cpu for which the callback should be invoked
* @step: The step in the state machine
* @cb: The callback function to invoke
*
* Called from cpu hotplug and from the state register machinery
*/
static int cpuhp_invoke_callback(unsigned int cpu, enum cpuhp_state step,
int (*cb)(unsigned int))
{
struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
int ret = 0;
if (cb) {
trace_cpuhp_enter(cpu, st->target, step, cb);
ret = cb(cpu);
trace_cpuhp_exit(cpu, st->state, step, ret);
}
return ret;
}
#ifdef CONFIG_SMP
/* Serializes the updates to cpu_online_mask, cpu_present_mask */
static DEFINE_MUTEX(cpu_add_remove_lock);
bool cpuhp_tasks_frozen;
EXPORT_SYMBOL_GPL(cpuhp_tasks_frozen);
/*
* The following two APIs (cpu_maps_update_begin/done) must be used when
* attempting to serialize the updates to cpu_online_mask & cpu_present_mask.
* The APIs cpu_notifier_register_begin/done() must be used to protect CPU
* hotplug callback (un)registration performed using __register_cpu_notifier()
* or __unregister_cpu_notifier().
*/
void cpu_maps_update_begin(void)
{
mutex_lock(&cpu_add_remove_lock);
}
EXPORT_SYMBOL(cpu_notifier_register_begin);
void cpu_maps_update_done(void)
{
mutex_unlock(&cpu_add_remove_lock);
}
EXPORT_SYMBOL(cpu_notifier_register_done);
static RAW_NOTIFIER_HEAD(cpu_chain);
/* If set, cpu_up and cpu_down will return -EBUSY and do nothing.
* Should always be manipulated under cpu_add_remove_lock
*/
static int cpu_hotplug_disabled;
#ifdef CONFIG_HOTPLUG_CPU
static struct {
struct task_struct *active_writer;
/* wait queue to wake up the active_writer */
wait_queue_head_t wq;
/* verifies that no writer will get active while readers are active */
struct mutex lock;
/*
* Also blocks the new readers during
* an ongoing cpu hotplug operation.
*/
atomic_t refcount;
#ifdef CONFIG_DEBUG_LOCK_ALLOC
struct lockdep_map dep_map;
#endif
} cpu_hotplug = {
.active_writer = NULL,
.wq = __WAIT_QUEUE_HEAD_INITIALIZER(cpu_hotplug.wq),
.lock = __MUTEX_INITIALIZER(cpu_hotplug.lock),
#ifdef CONFIG_DEBUG_LOCK_ALLOC
.dep_map = {.name = "cpu_hotplug.lock" },
#endif
};
/* Lockdep annotations for get/put_online_cpus() and cpu_hotplug_begin/end() */
#define cpuhp_lock_acquire_read() lock_map_acquire_read(&cpu_hotplug.dep_map)
#define cpuhp_lock_acquire_tryread() \
lock_map_acquire_tryread(&cpu_hotplug.dep_map)
#define cpuhp_lock_acquire() lock_map_acquire(&cpu_hotplug.dep_map)
#define cpuhp_lock_release() lock_map_release(&cpu_hotplug.dep_map)
void get_online_cpus(void)
{
might_sleep();
if (cpu_hotplug.active_writer == current)
return;
cpuhp_lock_acquire_read();
mutex_lock(&cpu_hotplug.lock);
atomic_inc(&cpu_hotplug.refcount);
mutex_unlock(&cpu_hotplug.lock);
}
EXPORT_SYMBOL_GPL(get_online_cpus);
void put_online_cpus(void)
{
int refcount;
if (cpu_hotplug.active_writer == current)
return;
refcount = atomic_dec_return(&cpu_hotplug.refcount);
if (WARN_ON(refcount < 0)) /* try to fix things up */
atomic_inc(&cpu_hotplug.refcount);
if (refcount <= 0 && waitqueue_active(&cpu_hotplug.wq))
wake_up(&cpu_hotplug.wq);
cpuhp_lock_release();
}
EXPORT_SYMBOL_GPL(put_online_cpus);
/*
* This ensures that the hotplug operation can begin only when the
* refcount goes to zero.
*
* Note that during a cpu-hotplug operation, the new readers, if any,
* will be blocked by the cpu_hotplug.lock
*
* Since cpu_hotplug_begin() is always called after invoking
* cpu_maps_update_begin(), we can be sure that only one writer is active.
*
* Note that theoretically, there is a possibility of a livelock:
* - Refcount goes to zero, last reader wakes up the sleeping
* writer.
* - Last reader unlocks the cpu_hotplug.lock.
* - A new reader arrives at this moment, bumps up the refcount.
* - The writer acquires the cpu_hotplug.lock finds the refcount
* non zero and goes to sleep again.
*
* However, this is very difficult to achieve in practice since
* get_online_cpus() not an api which is called all that often.
*
*/
void cpu_hotplug_begin(void)
{
DEFINE_WAIT(wait);
cpu_hotplug.active_writer = current;
cpuhp_lock_acquire();
for (;;) {
mutex_lock(&cpu_hotplug.lock);
prepare_to_wait(&cpu_hotplug.wq, &wait, TASK_UNINTERRUPTIBLE);
if (likely(!atomic_read(&cpu_hotplug.refcount)))
break;
mutex_unlock(&cpu_hotplug.lock);
schedule();
}
finish_wait(&cpu_hotplug.wq, &wait);
}
void cpu_hotplug_done(void)
{
cpu_hotplug.active_writer = NULL;
mutex_unlock(&cpu_hotplug.lock);
cpuhp_lock_release();
}
/*
* Wait for currently running CPU hotplug operations to complete (if any) and
* disable future CPU hotplug (from sysfs). The 'cpu_add_remove_lock' protects
* the 'cpu_hotplug_disabled' flag. The same lock is also acquired by the
* hotplug path before performing hotplug operations. So acquiring that lock
* guarantees mutual exclusion from any currently running hotplug operations.
*/
void cpu_hotplug_disable(void)
{
cpu_maps_update_begin();
cpu_hotplug_disabled++;
cpu_maps_update_done();
}
EXPORT_SYMBOL_GPL(cpu_hotplug_disable);
void cpu_hotplug_enable(void)
{
cpu_maps_update_begin();
WARN_ON(--cpu_hotplug_disabled < 0);
cpu_maps_update_done();
}
EXPORT_SYMBOL_GPL(cpu_hotplug_enable);
#endif /* CONFIG_HOTPLUG_CPU */
/* Need to know about CPUs going up/down? */
int register_cpu_notifier(struct notifier_block *nb)
{
int ret;
cpu_maps_update_begin();
ret = raw_notifier_chain_register(&cpu_chain, nb);
cpu_maps_update_done();
return ret;
}
int __register_cpu_notifier(struct notifier_block *nb)
{
return raw_notifier_chain_register(&cpu_chain, nb);
}
static int __cpu_notify(unsigned long val, unsigned int cpu, int nr_to_call,
int *nr_calls)
{
unsigned long mod = cpuhp_tasks_frozen ? CPU_TASKS_FROZEN : 0;
void *hcpu = (void *)(long)cpu;
int ret;
ret = __raw_notifier_call_chain(&cpu_chain, val | mod, hcpu, nr_to_call,
nr_calls);
return notifier_to_errno(ret);
}
static int cpu_notify(unsigned long val, unsigned int cpu)
{
return __cpu_notify(val, cpu, -1, NULL);
}
/* Notifier wrappers for transitioning to state machine */
static int notify_prepare(unsigned int cpu)
{
int nr_calls = 0;
int ret;
ret = __cpu_notify(CPU_UP_PREPARE, cpu, -1, &nr_calls);
if (ret) {
nr_calls--;
printk(KERN_WARNING "%s: attempt to bring up CPU %u failed\n",
__func__, cpu);
__cpu_notify(CPU_UP_CANCELED, cpu, nr_calls, NULL);
}
return ret;
}
static int notify_online(unsigned int cpu)
{
cpu_notify(CPU_ONLINE, cpu);
return 0;
}
static int notify_starting(unsigned int cpu)
{
cpu_notify(CPU_STARTING, cpu);
return 0;
}
static int bringup_cpu(unsigned int cpu)
{
struct task_struct *idle = idle_thread_get(cpu);
int ret;
/* Arch-specific enabling code. */
ret = __cpu_up(cpu, idle);
if (ret) {
cpu_notify(CPU_UP_CANCELED, cpu);
return ret;
}
BUG_ON(!cpu_online(cpu));
return 0;
}
#ifdef CONFIG_HOTPLUG_CPU
EXPORT_SYMBOL(register_cpu_notifier);
EXPORT_SYMBOL(__register_cpu_notifier);
void unregister_cpu_notifier(struct notifier_block *nb)
{
cpu_maps_update_begin();
raw_notifier_chain_unregister(&cpu_chain, nb);
cpu_maps_update_done();
}
EXPORT_SYMBOL(unregister_cpu_notifier);
void __unregister_cpu_notifier(struct notifier_block *nb)
{
raw_notifier_chain_unregister(&cpu_chain, nb);
}
EXPORT_SYMBOL(__unregister_cpu_notifier);
/**
* clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
* @cpu: a CPU id
*
* This function walks all processes, finds a valid mm struct for each one and
* then clears a corresponding bit in mm's cpumask. While this all sounds
* trivial, there are various non-obvious corner cases, which this function
* tries to solve in a safe manner.
*
* Also note that the function uses a somewhat relaxed locking scheme, so it may
* be called only for an already offlined CPU.
*/
void clear_tasks_mm_cpumask(int cpu)
{
struct task_struct *p;
/*
* This function is called after the cpu is taken down and marked
* offline, so its not like new tasks will ever get this cpu set in
* their mm mask. -- Peter Zijlstra
* Thus, we may use rcu_read_lock() here, instead of grabbing
* full-fledged tasklist_lock.
*/
WARN_ON(cpu_online(cpu));
rcu_read_lock();
for_each_process(p) {
struct task_struct *t;
/*
* Main thread might exit, but other threads may still have
* a valid mm. Find one.
*/
t = find_lock_task_mm(p);
if (!t)
continue;
cpumask_clear_cpu(cpu, mm_cpumask(t->mm));
task_unlock(t);
}
rcu_read_unlock();
}
static inline void check_for_tasks(int dead_cpu)
{
struct task_struct *g, *p;
read_lock(&tasklist_lock);
for_each_process_thread(g, p) {
if (!p->on_rq)
continue;
/*
* We do the check with unlocked task_rq(p)->lock.
* Order the reading to do not warn about a task,
* which was running on this cpu in the past, and
* it's just been woken on another cpu.
*/
rmb();
if (task_cpu(p) != dead_cpu)
continue;
pr_warn("Task %s (pid=%d) is on cpu %d (state=%ld, flags=%x)\n",
p->comm, task_pid_nr(p), dead_cpu, p->state, p->flags);
}
read_unlock(&tasklist_lock);
}
static void cpu_notify_nofail(unsigned long val, unsigned int cpu)
{
BUG_ON(cpu_notify(val, cpu));
}
static int notify_down_prepare(unsigned int cpu)
{
int err, nr_calls = 0;
err = __cpu_notify(CPU_DOWN_PREPARE, cpu, -1, &nr_calls);
if (err) {
nr_calls--;
__cpu_notify(CPU_DOWN_FAILED, cpu, nr_calls, NULL);
pr_warn("%s: attempt to take down CPU %u failed\n",
__func__, cpu);
}
return err;
}
static int notify_dying(unsigned int cpu)
{
cpu_notify(CPU_DYING, cpu);
return 0;
}
/* Take this CPU down. */
static int take_cpu_down(void *_param)
{
struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
enum cpuhp_state target = max((int)st->target, CPUHP_AP_OFFLINE);
int err, cpu = smp_processor_id();
/* Ensure this CPU doesn't handle any more interrupts. */
err = __cpu_disable();
if (err < 0)
return err;
/* Invoke the former CPU_DYING callbacks */
for (; st->state > target; st->state--) {
struct cpuhp_step *step = cpuhp_ap_states + st->state;
cpuhp_invoke_callback(cpu, st->state, step->teardown);
}
/* Give up timekeeping duties */
tick_handover_do_timer();
/* Park the stopper thread */
stop_machine_park(cpu);
return 0;
}
static int takedown_cpu(unsigned int cpu)
{
int err;
/*
* By now we've cleared cpu_active_mask, wait for all preempt-disabled
* and RCU users of this state to go away such that all new such users
* will observe it.
*
* For CONFIG_PREEMPT we have preemptible RCU and its sync_rcu() might
* not imply sync_sched(), so wait for both.
*
* Do sync before park smpboot threads to take care the rcu boost case.
*/
if (IS_ENABLED(CONFIG_PREEMPT))
synchronize_rcu_mult(call_rcu, call_rcu_sched);
else
synchronize_rcu();
smpboot_park_threads(cpu);
/*
* Prevent irq alloc/free while the dying cpu reorganizes the
* interrupt affinities.
*/
irq_lock_sparse();
/*
* So now all preempt/rcu users must observe !cpu_active().
*/
err = stop_machine(take_cpu_down, NULL, cpumask_of(cpu));
if (err) {
/* CPU didn't die: tell everyone. Can't complain. */
cpu_notify_nofail(CPU_DOWN_FAILED, cpu);
irq_unlock_sparse();
return err;
}
BUG_ON(cpu_online(cpu));
/*
* The migration_call() CPU_DYING callback will have removed all
* runnable tasks from the cpu, there's only the idle task left now
* that the migration thread is done doing the stop_machine thing.
*
* Wait for the stop thread to go away.
*/
while (!per_cpu(cpu_dead_idle, cpu))
cpu_relax();
smp_mb(); /* Read from cpu_dead_idle before __cpu_die(). */
per_cpu(cpu_dead_idle, cpu) = false;
/* Interrupts are moved away from the dying cpu, reenable alloc/free */
irq_unlock_sparse();
hotplug_cpu__broadcast_tick_pull(cpu);
/* This actually kills the CPU. */
__cpu_die(cpu);
tick_cleanup_dead_cpu(cpu);
return 0;
}
static int notify_dead(unsigned int cpu)
{
cpu_notify_nofail(CPU_DEAD, cpu);
check_for_tasks(cpu);
return 0;
}
#else
#define notify_down_prepare NULL
#define takedown_cpu NULL
#define notify_dead NULL
#define notify_dying NULL
#endif
#ifdef CONFIG_HOTPLUG_CPU
static void undo_cpu_down(unsigned int cpu, struct cpuhp_cpu_state *st)
{
for (st->state++; st->state < st->target; st->state++) {
struct cpuhp_step *step = cpuhp_bp_states + st->state;
if (!step->skip_onerr)
cpuhp_invoke_callback(cpu, st->state, step->startup);
}
}
/* Requires cpu_add_remove_lock to be held */
static int __ref _cpu_down(unsigned int cpu, int tasks_frozen,
enum cpuhp_state target)
{
struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
int prev_state, ret = 0;
bool hasdied = false;
if (num_online_cpus() == 1)
return -EBUSY;
if (!cpu_present(cpu))
return -EINVAL;
cpu_hotplug_begin();
cpuhp_tasks_frozen = tasks_frozen;
prev_state = st->state;
st->target = target;
for (; st->state > st->target; st->state--) {
struct cpuhp_step *step = cpuhp_bp_states + st->state;
ret = cpuhp_invoke_callback(cpu, st->state, step->teardown);
if (ret) {
st->target = prev_state;
undo_cpu_down(cpu, st);
break;
}
}
hasdied = prev_state != st->state && st->state == CPUHP_OFFLINE;
cpu_hotplug_done();
/* This post dead nonsense must die */
if (!ret && hasdied)
cpu_notify_nofail(CPU_POST_DEAD, cpu);
return ret;
}
static int do_cpu_down(unsigned int cpu, enum cpuhp_state target)
{
int err;
cpu_maps_update_begin();
if (cpu_hotplug_disabled) {
err = -EBUSY;
goto out;
}
err = _cpu_down(cpu, 0, target);
out:
cpu_maps_update_done();
return err;
}
int cpu_down(unsigned int cpu)
{
return do_cpu_down(cpu, CPUHP_OFFLINE);
}
EXPORT_SYMBOL(cpu_down);
#endif /*CONFIG_HOTPLUG_CPU*/
/*
* Unpark per-CPU smpboot kthreads at CPU-online time.
*/
static int smpboot_thread_call(struct notifier_block *nfb,
unsigned long action, void *hcpu)
{
int cpu = (long)hcpu;
switch (action & ~CPU_TASKS_FROZEN) {
case CPU_DOWN_FAILED:
case CPU_ONLINE:
smpboot_unpark_threads(cpu);
break;
default:
break;
}
return NOTIFY_OK;
}
static struct notifier_block smpboot_thread_notifier = {
.notifier_call = smpboot_thread_call,
.priority = CPU_PRI_SMPBOOT,
};
void smpboot_thread_init(void)
{
register_cpu_notifier(&smpboot_thread_notifier);
}
/**
* notify_cpu_starting(cpu) - call the CPU_STARTING notifiers
* @cpu: cpu that just started
*
* This function calls the cpu_chain notifiers with CPU_STARTING.
* It must be called by the arch code on the new cpu, before the new cpu
* enables interrupts and before the "boot" cpu returns from __cpu_up().
*/
void notify_cpu_starting(unsigned int cpu)
{
struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
enum cpuhp_state target = min((int)st->target, CPUHP_AP_ONLINE);
while (st->state < target) {
struct cpuhp_step *step;
st->state++;
step = cpuhp_ap_states + st->state;
cpuhp_invoke_callback(cpu, st->state, step->startup);
}
}
static void undo_cpu_up(unsigned int cpu, struct cpuhp_cpu_state *st)
{
for (st->state--; st->state > st->target; st->state--) {
struct cpuhp_step *step = cpuhp_bp_states + st->state;
if (!step->skip_onerr)
cpuhp_invoke_callback(cpu, st->state, step->teardown);
}
}
/* Requires cpu_add_remove_lock to be held */
static int _cpu_up(unsigned int cpu, int tasks_frozen, enum cpuhp_state target)
{
struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
struct task_struct *idle;
int prev_state, ret = 0;
cpu_hotplug_begin();
if (!cpu_present(cpu)) {
ret = -EINVAL;
goto out;
}
/*
* The caller of do_cpu_up might have raced with another
* caller. Ignore it for now.
*/
if (st->state >= target)
goto out;
if (st->state == CPUHP_OFFLINE) {
/* Let it fail before we try to bring the cpu up */
idle = idle_thread_get(cpu);
if (IS_ERR(idle)) {
ret = PTR_ERR(idle);
goto out;
}
}
cpuhp_tasks_frozen = tasks_frozen;
prev_state = st->state;
st->target = target;
while (st->state < st->target) {
struct cpuhp_step *step;
st->state++;
step = cpuhp_bp_states + st->state;
ret = cpuhp_invoke_callback(cpu, st->state, step->startup);
if (ret) {
st->target = prev_state;
undo_cpu_up(cpu, st);
break;
}
}
out:
cpu_hotplug_done();
return ret;
}
static int do_cpu_up(unsigned int cpu, enum cpuhp_state target)
{
int err = 0;
if (!cpu_possible(cpu)) {
pr_err("can't online cpu %d because it is not configured as may-hotadd at boot time\n",
cpu);
#if defined(CONFIG_IA64)
pr_err("please check additional_cpus= boot parameter\n");
#endif
return -EINVAL;
}
err = try_online_node(cpu_to_node(cpu));
if (err)
return err;
cpu_maps_update_begin();
if (cpu_hotplug_disabled) {
err = -EBUSY;
goto out;
}
err = _cpu_up(cpu, 0, target);
out:
cpu_maps_update_done();
return err;
}
int cpu_up(unsigned int cpu)
{
return do_cpu_up(cpu, CPUHP_ONLINE);
}
EXPORT_SYMBOL_GPL(cpu_up);
#ifdef CONFIG_PM_SLEEP_SMP
static cpumask_var_t frozen_cpus;
int disable_nonboot_cpus(void)
{
int cpu, first_cpu, error = 0;
cpu_maps_update_begin();
first_cpu = cpumask_first(cpu_online_mask);
/*
* We take down all of the non-boot CPUs in one shot to avoid races
* with the userspace trying to use the CPU hotplug at the same time
*/
cpumask_clear(frozen_cpus);
pr_info("Disabling non-boot CPUs ...\n");
for_each_online_cpu(cpu) {
if (cpu == first_cpu)
continue;
trace_suspend_resume(TPS("CPU_OFF"), cpu, true);
error = _cpu_down(cpu, 1, CPUHP_OFFLINE);
trace_suspend_resume(TPS("CPU_OFF"), cpu, false);
if (!error)
cpumask_set_cpu(cpu, frozen_cpus);
else {
pr_err("Error taking CPU%d down: %d\n", cpu, error);
break;
}
}
if (!error)
BUG_ON(num_online_cpus() > 1);
else
pr_err("Non-boot CPUs are not disabled\n");
/*
* Make sure the CPUs won't be enabled by someone else. We need to do
* this even in case of failure as all disable_nonboot_cpus() users are
* supposed to do enable_nonboot_cpus() on the failure path.
*/
cpu_hotplug_disabled++;
cpu_maps_update_done();
return error;
}
void __weak arch_enable_nonboot_cpus_begin(void)
{
}
void __weak arch_enable_nonboot_cpus_end(void)
{
}
void enable_nonboot_cpus(void)
{
int cpu, error;
/* Allow everyone to use the CPU hotplug again */
cpu_maps_update_begin();
WARN_ON(--cpu_hotplug_disabled < 0);
if (cpumask_empty(frozen_cpus))
goto out;
pr_info("Enabling non-boot CPUs ...\n");
arch_enable_nonboot_cpus_begin();
for_each_cpu(cpu, frozen_cpus) {
trace_suspend_resume(TPS("CPU_ON"), cpu, true);
error = _cpu_up(cpu, 1, CPUHP_ONLINE);
trace_suspend_resume(TPS("CPU_ON"), cpu, false);
if (!error) {
pr_info("CPU%d is up\n", cpu);
continue;
}
pr_warn("Error taking CPU%d up: %d\n", cpu, error);
}
arch_enable_nonboot_cpus_end();
cpumask_clear(frozen_cpus);
out:
cpu_maps_update_done();
}
static int __init alloc_frozen_cpus(void)
{
if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
return -ENOMEM;
return 0;
}
core_initcall(alloc_frozen_cpus);
/*
* When callbacks for CPU hotplug notifications are being executed, we must
* ensure that the state of the system with respect to the tasks being frozen
* or not, as reported by the notification, remains unchanged *throughout the
* duration* of the execution of the callbacks.
* Hence we need to prevent the freezer from racing with regular CPU hotplug.
*
* This synchronization is implemented by mutually excluding regular CPU
* hotplug and Suspend/Hibernate call paths by hooking onto the Suspend/
* Hibernate notifications.
*/
static int
cpu_hotplug_pm_callback(struct notifier_block *nb,
unsigned long action, void *ptr)
{
switch (action) {
case PM_SUSPEND_PREPARE:
case PM_HIBERNATION_PREPARE:
cpu_hotplug_disable();
break;
case PM_POST_SUSPEND:
case PM_POST_HIBERNATION:
cpu_hotplug_enable();
break;
default:
return NOTIFY_DONE;
}
return NOTIFY_OK;
}
static int __init cpu_hotplug_pm_sync_init(void)
{
/*
* cpu_hotplug_pm_callback has higher priority than x86
* bsp_pm_callback which depends on cpu_hotplug_pm_callback
* to disable cpu hotplug to avoid cpu hotplug race.
*/
pm_notifier(cpu_hotplug_pm_callback, 0);
return 0;
}
core_initcall(cpu_hotplug_pm_sync_init);
#endif /* CONFIG_PM_SLEEP_SMP */
#endif /* CONFIG_SMP */
/* Boot processor state steps */
static struct cpuhp_step cpuhp_bp_states[] = {
[CPUHP_OFFLINE] = {
.name = "offline",
.startup = NULL,
.teardown = NULL,
},
#ifdef CONFIG_SMP
[CPUHP_CREATE_THREADS]= {
.name = "threads:create",
.startup = smpboot_create_threads,
.teardown = NULL,
.cant_stop = true,
},
[CPUHP_NOTIFY_PREPARE] = {
.name = "notify:prepare",
.startup = notify_prepare,
.teardown = notify_dead,
.skip_onerr = true,
.cant_stop = true,
},
[CPUHP_BRINGUP_CPU] = {
.name = "cpu:bringup",
.startup = bringup_cpu,
.teardown = NULL,
.cant_stop = true,
},
[CPUHP_TEARDOWN_CPU] = {
.name = "cpu:teardown",
.startup = NULL,
.teardown = takedown_cpu,
.cant_stop = true,
},
[CPUHP_NOTIFY_ONLINE] = {
.name = "notify:online",
.startup = notify_online,
.teardown = notify_down_prepare,
.cant_stop = true,
},
#endif
[CPUHP_ONLINE] = {
.name = "online",
.startup = NULL,
.teardown = NULL,
},
};
/* Application processor state steps */
static struct cpuhp_step cpuhp_ap_states[] = {
#ifdef CONFIG_SMP
[CPUHP_AP_NOTIFY_STARTING] = {
.name = "notify:starting",
.startup = notify_starting,
.teardown = notify_dying,
.skip_onerr = true,
.cant_stop = true,
},
#endif
[CPUHP_ONLINE] = {
.name = "online",
.startup = NULL,
.teardown = NULL,
},
};
static bool cpuhp_is_ap_state(enum cpuhp_state state)
{
return (state > CPUHP_AP_OFFLINE && state < CPUHP_AP_ONLINE);
}
static struct cpuhp_step *cpuhp_get_step(enum cpuhp_state state)
{
struct cpuhp_step *sp;
sp = cpuhp_is_ap_state(state) ? cpuhp_ap_states : cpuhp_bp_states;
return sp + state;
}
#if defined(CONFIG_SYSFS) && defined(CONFIG_HOTPLUG_CPU)
static ssize_t show_cpuhp_state(struct device *dev,
struct device_attribute *attr, char *buf)
{
struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
return sprintf(buf, "%d\n", st->state);
}
static DEVICE_ATTR(state, 0444, show_cpuhp_state, NULL);
static ssize_t write_cpuhp_target(struct device *dev,
struct device_attribute *attr,
const char *buf, size_t count)
{
struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
struct cpuhp_step *sp;
int target, ret;
ret = kstrtoint(buf, 10, &target);
if (ret)
return ret;
#ifdef CONFIG_CPU_HOTPLUG_STATE_CONTROL
if (target < CPUHP_OFFLINE || target > CPUHP_ONLINE)
return -EINVAL;
#else
if (target != CPUHP_OFFLINE && target != CPUHP_ONLINE)
return -EINVAL;
#endif
ret = lock_device_hotplug_sysfs();
if (ret)
return ret;
mutex_lock(&cpuhp_state_mutex);
sp = cpuhp_get_step(target);
ret = !sp->name || sp->cant_stop ? -EINVAL : 0;
mutex_unlock(&cpuhp_state_mutex);
if (ret)
return ret;
if (st->state < target)
ret = do_cpu_up(dev->id, target);
else
ret = do_cpu_down(dev->id, target);
unlock_device_hotplug();
return ret ? ret : count;
}
static ssize_t show_cpuhp_target(struct device *dev,
struct device_attribute *attr, char *buf)
{
struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
return sprintf(buf, "%d\n", st->target);
}
static DEVICE_ATTR(target, 0644, show_cpuhp_target, write_cpuhp_target);
static struct attribute *cpuhp_cpu_attrs[] = {
&dev_attr_state.attr,
&dev_attr_target.attr,
NULL
};
static struct attribute_group cpuhp_cpu_attr_group = {
.attrs = cpuhp_cpu_attrs,
.name = "hotplug",
NULL
};
static ssize_t show_cpuhp_states(struct device *dev,
struct device_attribute *attr, char *buf)
{
ssize_t cur, res = 0;
int i;
mutex_lock(&cpuhp_state_mutex);
for (i = CPUHP_OFFLINE; i <= CPUHP_ONLINE; i++) {
struct cpuhp_step *sp = cpuhp_get_step(i);
if (sp->name) {
cur = sprintf(buf, "%3d: %s\n", i, sp->name);
buf += cur;
res += cur;
}
}
mutex_unlock(&cpuhp_state_mutex);
return res;
}
static DEVICE_ATTR(states, 0444, show_cpuhp_states, NULL);
static struct attribute *cpuhp_cpu_root_attrs[] = {
&dev_attr_states.attr,
NULL
};
static struct attribute_group cpuhp_cpu_root_attr_group = {
.attrs = cpuhp_cpu_root_attrs,
.name = "hotplug",
NULL
};
static int __init cpuhp_sysfs_init(void)
{
int cpu, ret;
ret = sysfs_create_group(&cpu_subsys.dev_root->kobj,
&cpuhp_cpu_root_attr_group);
if (ret)
return ret;
for_each_possible_cpu(cpu) {
struct device *dev = get_cpu_device(cpu);
if (!dev)
continue;
ret = sysfs_create_group(&dev->kobj, &cpuhp_cpu_attr_group);
if (ret)
return ret;
}
return 0;
}
device_initcall(cpuhp_sysfs_init);
#endif
/*
* cpu_bit_bitmap[] is a special, "compressed" data structure that
* represents all NR_CPUS bits binary values of 1<<nr.
*
* It is used by cpumask_of() to get a constant address to a CPU
* mask value that has a single bit set only.
*/
/* cpu_bit_bitmap[0] is empty - so we can back into it */
#define MASK_DECLARE_1(x) [x+1][0] = (1UL << (x))
#define MASK_DECLARE_2(x) MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
#define MASK_DECLARE_4(x) MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
#define MASK_DECLARE_8(x) MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
MASK_DECLARE_8(0), MASK_DECLARE_8(8),
MASK_DECLARE_8(16), MASK_DECLARE_8(24),
#if BITS_PER_LONG > 32
MASK_DECLARE_8(32), MASK_DECLARE_8(40),
MASK_DECLARE_8(48), MASK_DECLARE_8(56),
#endif
};
EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
EXPORT_SYMBOL(cpu_all_bits);
#ifdef CONFIG_INIT_ALL_POSSIBLE
struct cpumask __cpu_possible_mask __read_mostly
= {CPU_BITS_ALL};
#else
struct cpumask __cpu_possible_mask __read_mostly;
#endif
EXPORT_SYMBOL(__cpu_possible_mask);
struct cpumask __cpu_online_mask __read_mostly;
EXPORT_SYMBOL(__cpu_online_mask);
struct cpumask __cpu_present_mask __read_mostly;
EXPORT_SYMBOL(__cpu_present_mask);
struct cpumask __cpu_active_mask __read_mostly;
EXPORT_SYMBOL(__cpu_active_mask);
void init_cpu_present(const struct cpumask *src)
{
cpumask_copy(&__cpu_present_mask, src);
}
void init_cpu_possible(const struct cpumask *src)
{
cpumask_copy(&__cpu_possible_mask, src);
}
void init_cpu_online(const struct cpumask *src)
{
cpumask_copy(&__cpu_online_mask, src);
}
/*
* Activate the first processor.
*/
void __init boot_cpu_init(void)
{
int cpu = smp_processor_id();
/* Mark the boot cpu "present", "online" etc for SMP and UP case */
set_cpu_online(cpu, true);
set_cpu_active(cpu, true);
set_cpu_present(cpu, true);
set_cpu_possible(cpu, true);
}
/*
* Must be called _AFTER_ setting up the per_cpu areas
*/
void __init boot_cpu_state_init(void)
{
per_cpu_ptr(&cpuhp_state, smp_processor_id())->state = CPUHP_ONLINE;
}