- 根目录:
- kernel
- time
- timer.c
/*
* linux/kernel/timer.c
*
* Kernel internal timers
*
* Copyright (C) 1991, 1992 Linus Torvalds
*
* 1997-01-28 Modified by Finn Arne Gangstad to make timers scale better.
*
* 1997-09-10 Updated NTP code according to technical memorandum Jan '96
* "A Kernel Model for Precision Timekeeping" by Dave Mills
* 1998-12-24 Fixed a xtime SMP race (we need the xtime_lock rw spinlock to
* serialize accesses to xtime/lost_ticks).
* Copyright (C) 1998 Andrea Arcangeli
* 1999-03-10 Improved NTP compatibility by Ulrich Windl
* 2002-05-31 Move sys_sysinfo here and make its locking sane, Robert Love
* 2000-10-05 Implemented scalable SMP per-CPU timer handling.
* Copyright (C) 2000, 2001, 2002 Ingo Molnar
* Designed by David S. Miller, Alexey Kuznetsov and Ingo Molnar
*/
#include <linux/kernel_stat.h>
#include <linux/export.h>
#include <linux/interrupt.h>
#include <linux/percpu.h>
#include <linux/init.h>
#include <linux/mm.h>
#include <linux/swap.h>
#include <linux/pid_namespace.h>
#include <linux/notifier.h>
#include <linux/thread_info.h>
#include <linux/time.h>
#include <linux/jiffies.h>
#include <linux/posix-timers.h>
#include <linux/cpu.h>
#include <linux/syscalls.h>
#include <linux/delay.h>
#include <linux/tick.h>
#include <linux/kallsyms.h>
#include <linux/irq_work.h>
#include <linux/sched.h>
#include <linux/sched/sysctl.h>
#include <linux/slab.h>
#include <linux/compat.h>
#include <asm/uaccess.h>
#include <asm/unistd.h>
#include <asm/div64.h>
#include <asm/timex.h>
#include <asm/io.h>
#include "tick-internal.h"
#define CREATE_TRACE_POINTS
#include <trace/events/timer.h>
__visible u64 jiffies_64 __cacheline_aligned_in_smp = INITIAL_JIFFIES;
EXPORT_SYMBOL(jiffies_64);
/*
* per-CPU timer vector definitions:
*/
#define TVN_BITS (CONFIG_BASE_SMALL ? 4 : 6)
#define TVR_BITS (CONFIG_BASE_SMALL ? 6 : 8)
#define TVN_SIZE (1 << TVN_BITS)
#define TVR_SIZE (1 << TVR_BITS)
#define TVN_MASK (TVN_SIZE - 1)
#define TVR_MASK (TVR_SIZE - 1)
#define MAX_TVAL ((unsigned long)((1ULL << (TVR_BITS + 4*TVN_BITS)) - 1))
struct tvec {
struct hlist_head vec[TVN_SIZE];
};
struct tvec_root {
struct hlist_head vec[TVR_SIZE];
};
struct tvec_base {
spinlock_t lock;
struct timer_list *running_timer;
unsigned long timer_jiffies;
unsigned long next_timer;
unsigned long active_timers;
unsigned long all_timers;
int cpu;
bool migration_enabled;
bool nohz_active;
struct tvec_root tv1;
struct tvec tv2;
struct tvec tv3;
struct tvec tv4;
struct tvec tv5;
} ____cacheline_aligned;
static DEFINE_PER_CPU(struct tvec_base, tvec_bases);
#if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ_COMMON)
unsigned int sysctl_timer_migration = 1;
void timers_update_migration(bool update_nohz)
{
bool on = sysctl_timer_migration && tick_nohz_active;
unsigned int cpu;
/* Avoid the loop, if nothing to update */
if (this_cpu_read(tvec_bases.migration_enabled) == on)
return;
for_each_possible_cpu(cpu) {
per_cpu(tvec_bases.migration_enabled, cpu) = on;
per_cpu(hrtimer_bases.migration_enabled, cpu) = on;
if (!update_nohz)
continue;
per_cpu(tvec_bases.nohz_active, cpu) = true;
per_cpu(hrtimer_bases.nohz_active, cpu) = true;
}
}
int timer_migration_handler(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp,
loff_t *ppos)
{
static DEFINE_MUTEX(mutex);
int ret;
mutex_lock(&mutex);
ret = proc_dointvec(table, write, buffer, lenp, ppos);
if (!ret && write)
timers_update_migration(false);
mutex_unlock(&mutex);
return ret;
}
static inline struct tvec_base *get_target_base(struct tvec_base *base,
int pinned)
{
if (pinned || !base->migration_enabled)
return this_cpu_ptr(&tvec_bases);
return per_cpu_ptr(&tvec_bases, get_nohz_timer_target());
}
#else
static inline struct tvec_base *get_target_base(struct tvec_base *base,
int pinned)
{
return this_cpu_ptr(&tvec_bases);
}
#endif
static unsigned long round_jiffies_common(unsigned long j, int cpu,
bool force_up)
{
int rem;
unsigned long original = j;
/*
* We don't want all cpus firing their timers at once hitting the
* same lock or cachelines, so we skew each extra cpu with an extra
* 3 jiffies. This 3 jiffies came originally from the mm/ code which
* already did this.
* The skew is done by adding 3*cpunr, then round, then subtract this
* extra offset again.
*/
j += cpu * 3;
rem = j % HZ;
/*
* If the target jiffie is just after a whole second (which can happen
* due to delays of the timer irq, long irq off times etc etc) then
* we should round down to the whole second, not up. Use 1/4th second
* as cutoff for this rounding as an extreme upper bound for this.
* But never round down if @force_up is set.
*/
if (rem < HZ/4 && !force_up) /* round down */
j = j - rem;
else /* round up */
j = j - rem + HZ;
/* now that we have rounded, subtract the extra skew again */
j -= cpu * 3;
/*
* Make sure j is still in the future. Otherwise return the
* unmodified value.
*/
return time_is_after_jiffies(j) ? j : original;
}
/**
* __round_jiffies - function to round jiffies to a full second
* @j: the time in (absolute) jiffies that should be rounded
* @cpu: the processor number on which the timeout will happen
*
* __round_jiffies() rounds an absolute time in the future (in jiffies)
* up or down to (approximately) full seconds. This is useful for timers
* for which the exact time they fire does not matter too much, as long as
* they fire approximately every X seconds.
*
* By rounding these timers to whole seconds, all such timers will fire
* at the same time, rather than at various times spread out. The goal
* of this is to have the CPU wake up less, which saves power.
*
* The exact rounding is skewed for each processor to avoid all
* processors firing at the exact same time, which could lead
* to lock contention or spurious cache line bouncing.
*
* The return value is the rounded version of the @j parameter.
*/
unsigned long __round_jiffies(unsigned long j, int cpu)
{
return round_jiffies_common(j, cpu, false);
}
EXPORT_SYMBOL_GPL(__round_jiffies);
/**
* __round_jiffies_relative - function to round jiffies to a full second
* @j: the time in (relative) jiffies that should be rounded
* @cpu: the processor number on which the timeout will happen
*
* __round_jiffies_relative() rounds a time delta in the future (in jiffies)
* up or down to (approximately) full seconds. This is useful for timers
* for which the exact time they fire does not matter too much, as long as
* they fire approximately every X seconds.
*
* By rounding these timers to whole seconds, all such timers will fire
* at the same time, rather than at various times spread out. The goal
* of this is to have the CPU wake up less, which saves power.
*
* The exact rounding is skewed for each processor to avoid all
* processors firing at the exact same time, which could lead
* to lock contention or spurious cache line bouncing.
*
* The return value is the rounded version of the @j parameter.
*/
unsigned long __round_jiffies_relative(unsigned long j, int cpu)
{
unsigned long j0 = jiffies;
/* Use j0 because jiffies might change while we run */
return round_jiffies_common(j + j0, cpu, false) - j0;
}
EXPORT_SYMBOL_GPL(__round_jiffies_relative);
/**
* round_jiffies - function to round jiffies to a full second
* @j: the time in (absolute) jiffies that should be rounded
*
* round_jiffies() rounds an absolute time in the future (in jiffies)
* up or down to (approximately) full seconds. This is useful for timers
* for which the exact time they fire does not matter too much, as long as
* they fire approximately every X seconds.
*
* By rounding these timers to whole seconds, all such timers will fire
* at the same time, rather than at various times spread out. The goal
* of this is to have the CPU wake up less, which saves power.
*
* The return value is the rounded version of the @j parameter.
*/
unsigned long round_jiffies(unsigned long j)
{
return round_jiffies_common(j, raw_smp_processor_id(), false);
}
EXPORT_SYMBOL_GPL(round_jiffies);
/**
* round_jiffies_relative - function to round jiffies to a full second
* @j: the time in (relative) jiffies that should be rounded
*
* round_jiffies_relative() rounds a time delta in the future (in jiffies)
* up or down to (approximately) full seconds. This is useful for timers
* for which the exact time they fire does not matter too much, as long as
* they fire approximately every X seconds.
*
* By rounding these timers to whole seconds, all such timers will fire
* at the same time, rather than at various times spread out. The goal
* of this is to have the CPU wake up less, which saves power.
*
* The return value is the rounded version of the @j parameter.
*/
unsigned long round_jiffies_relative(unsigned long j)
{
return __round_jiffies_relative(j, raw_smp_processor_id());
}
EXPORT_SYMBOL_GPL(round_jiffies_relative);
/**
* __round_jiffies_up - function to round jiffies up to a full second
* @j: the time in (absolute) jiffies that should be rounded
* @cpu: the processor number on which the timeout will happen
*
* This is the same as __round_jiffies() except that it will never
* round down. This is useful for timeouts for which the exact time
* of firing does not matter too much, as long as they don't fire too
* early.
*/
unsigned long __round_jiffies_up(unsigned long j, int cpu)
{
return round_jiffies_common(j, cpu, true);
}
EXPORT_SYMBOL_GPL(__round_jiffies_up);
/**
* __round_jiffies_up_relative - function to round jiffies up to a full second
* @j: the time in (relative) jiffies that should be rounded
* @cpu: the processor number on which the timeout will happen
*
* This is the same as __round_jiffies_relative() except that it will never
* round down. This is useful for timeouts for which the exact time
* of firing does not matter too much, as long as they don't fire too
* early.
*/
unsigned long __round_jiffies_up_relative(unsigned long j, int cpu)
{
unsigned long j0 = jiffies;
/* Use j0 because jiffies might change while we run */
return round_jiffies_common(j + j0, cpu, true) - j0;
}
EXPORT_SYMBOL_GPL(__round_jiffies_up_relative);
/**
* round_jiffies_up - function to round jiffies up to a full second
* @j: the time in (absolute) jiffies that should be rounded
*
* This is the same as round_jiffies() except that it will never
* round down. This is useful for timeouts for which the exact time
* of firing does not matter too much, as long as they don't fire too
* early.
*/
unsigned long round_jiffies_up(unsigned long j)
{
return round_jiffies_common(j, raw_smp_processor_id(), true);
}
EXPORT_SYMBOL_GPL(round_jiffies_up);
/**
* round_jiffies_up_relative - function to round jiffies up to a full second
* @j: the time in (relative) jiffies that should be rounded
*
* This is the same as round_jiffies_relative() except that it will never
* round down. This is useful for timeouts for which the exact time
* of firing does not matter too much, as long as they don't fire too
* early.
*/
unsigned long round_jiffies_up_relative(unsigned long j)
{
return __round_jiffies_up_relative(j, raw_smp_processor_id());
}
EXPORT_SYMBOL_GPL(round_jiffies_up_relative);
/**
* set_timer_slack - set the allowed slack for a timer
* @timer: the timer to be modified
* @slack_hz: the amount of time (in jiffies) allowed for rounding
*
* Set the amount of time, in jiffies, that a certain timer has
* in terms of slack. By setting this value, the timer subsystem
* will schedule the actual timer somewhere between
* the time mod_timer() asks for, and that time plus the slack.
*
* By setting the slack to -1, a percentage of the delay is used
* instead.
*/
void set_timer_slack(struct timer_list *timer, int slack_hz)
{
timer->slack = slack_hz;
}
EXPORT_SYMBOL_GPL(set_timer_slack);
static void
__internal_add_timer(struct tvec_base *base, struct timer_list *timer)
{
unsigned long expires = timer->expires;
unsigned long idx = expires - base->timer_jiffies;
struct hlist_head *vec;
if (idx < TVR_SIZE) {
int i = expires & TVR_MASK;
vec = base->tv1.vec + i;
} else if (idx < 1 << (TVR_BITS + TVN_BITS)) {
int i = (expires >> TVR_BITS) & TVN_MASK;
vec = base->tv2.vec + i;
} else if (idx < 1 << (TVR_BITS + 2 * TVN_BITS)) {
int i = (expires >> (TVR_BITS + TVN_BITS)) & TVN_MASK;
vec = base->tv3.vec + i;
} else if (idx < 1 << (TVR_BITS + 3 * TVN_BITS)) {
int i = (expires >> (TVR_BITS + 2 * TVN_BITS)) & TVN_MASK;
vec = base->tv4.vec + i;
} else if ((signed long) idx < 0) {
/*
* Can happen if you add a timer with expires == jiffies,
* or you set a timer to go off in the past
*/
vec = base->tv1.vec + (base->timer_jiffies & TVR_MASK);
} else {
int i;
/* If the timeout is larger than MAX_TVAL (on 64-bit
* architectures or with CONFIG_BASE_SMALL=1) then we
* use the maximum timeout.
*/
if (idx > MAX_TVAL) {
idx = MAX_TVAL;
expires = idx + base->timer_jiffies;
}
i = (expires >> (TVR_BITS + 3 * TVN_BITS)) & TVN_MASK;
vec = base->tv5.vec + i;
}
hlist_add_head(&timer->entry, vec);
}
static void internal_add_timer(struct tvec_base *base, struct timer_list *timer)
{
/* Advance base->jiffies, if the base is empty */
if (!base->all_timers++)
base->timer_jiffies = jiffies;
__internal_add_timer(base, timer);
/*
* Update base->active_timers and base->next_timer
*/
if (!(timer->flags & TIMER_DEFERRABLE)) {
if (!base->active_timers++ ||
time_before(timer->expires, base->next_timer))
base->next_timer = timer->expires;
}
/*
* Check whether the other CPU is in dynticks mode and needs
* to be triggered to reevaluate the timer wheel.
* We are protected against the other CPU fiddling
* with the timer by holding the timer base lock. This also
* makes sure that a CPU on the way to stop its tick can not
* evaluate the timer wheel.
*
* Spare the IPI for deferrable timers on idle targets though.
* The next busy ticks will take care of it. Except full dynticks
* require special care against races with idle_cpu(), lets deal
* with that later.
*/
if (base->nohz_active) {
if (!(timer->flags & TIMER_DEFERRABLE) ||
tick_nohz_full_cpu(base->cpu))
wake_up_nohz_cpu(base->cpu);
}
}
#ifdef CONFIG_TIMER_STATS
void __timer_stats_timer_set_start_info(struct timer_list *timer, void *addr)
{
if (timer->start_site)
return;
timer->start_site = addr;
memcpy(timer->start_comm, current->comm, TASK_COMM_LEN);
timer->start_pid = current->pid;
}
static void timer_stats_account_timer(struct timer_list *timer)
{
void *site;
/*
* start_site can be concurrently reset by
* timer_stats_timer_clear_start_info()
*/
site = READ_ONCE(timer->start_site);
if (likely(!site))
return;
timer_stats_update_stats(timer, timer->start_pid, site,
timer->function, timer->start_comm,
timer->flags);
}
#else
static void timer_stats_account_timer(struct timer_list *timer) {}
#endif
#ifdef CONFIG_DEBUG_OBJECTS_TIMERS
static struct debug_obj_descr timer_debug_descr;
static void *timer_debug_hint(void *addr)
{
return ((struct timer_list *) addr)->function;
}
/*
* fixup_init is called when:
* - an active object is initialized
*/
static int timer_fixup_init(void *addr, enum debug_obj_state state)
{
struct timer_list *timer = addr;
switch (state) {
case ODEBUG_STATE_ACTIVE:
del_timer_sync(timer);
debug_object_init(timer, &timer_debug_descr);
return 1;
default:
return 0;
}
}
/* Stub timer callback for improperly used timers. */
static void stub_timer(unsigned long data)
{
WARN_ON(1);
}
/*
* fixup_activate is called when:
* - an active object is activated
* - an unknown object is activated (might be a statically initialized object)
*/
static int timer_fixup_activate(void *addr, enum debug_obj_state state)
{
struct timer_list *timer = addr;
switch (state) {
case ODEBUG_STATE_NOTAVAILABLE:
/*
* This is not really a fixup. The timer was
* statically initialized. We just make sure that it
* is tracked in the object tracker.
*/
if (timer->entry.pprev == NULL &&
timer->entry.next == TIMER_ENTRY_STATIC) {
debug_object_init(timer, &timer_debug_descr);
debug_object_activate(timer, &timer_debug_descr);
return 0;
} else {
setup_timer(timer, stub_timer, 0);
return 1;
}
return 0;
case ODEBUG_STATE_ACTIVE:
WARN_ON(1);
default:
return 0;
}
}
/*
* fixup_free is called when:
* - an active object is freed
*/
static int timer_fixup_free(void *addr, enum debug_obj_state state)
{
struct timer_list *timer = addr;
switch (state) {
case ODEBUG_STATE_ACTIVE:
del_timer_sync(timer);
debug_object_free(timer, &timer_debug_descr);
return 1;
default:
return 0;
}
}
/*
* fixup_assert_init is called when:
* - an untracked/uninit-ed object is found
*/
static int timer_fixup_assert_init(void *addr, enum debug_obj_state state)
{
struct timer_list *timer = addr;
switch (state) {
case ODEBUG_STATE_NOTAVAILABLE:
if (timer->entry.next == TIMER_ENTRY_STATIC) {
/*
* This is not really a fixup. The timer was
* statically initialized. We just make sure that it
* is tracked in the object tracker.
*/
debug_object_init(timer, &timer_debug_descr);
return 0;
} else {
setup_timer(timer, stub_timer, 0);
return 1;
}
default:
return 0;
}
}
static struct debug_obj_descr timer_debug_descr = {
.name = "timer_list",
.debug_hint = timer_debug_hint,
.fixup_init = timer_fixup_init,
.fixup_activate = timer_fixup_activate,
.fixup_free = timer_fixup_free,
.fixup_assert_init = timer_fixup_assert_init,
};
static inline void debug_timer_init(struct timer_list *timer)
{
debug_object_init(timer, &timer_debug_descr);
}
static inline void debug_timer_activate(struct timer_list *timer)
{
debug_object_activate(timer, &timer_debug_descr);
}
static inline void debug_timer_deactivate(struct timer_list *timer)
{
debug_object_deactivate(timer, &timer_debug_descr);
}
static inline void debug_timer_free(struct timer_list *timer)
{
debug_object_free(timer, &timer_debug_descr);
}
static inline void debug_timer_assert_init(struct timer_list *timer)
{
debug_object_assert_init(timer, &timer_debug_descr);
}
static void do_init_timer(struct timer_list *timer, unsigned int flags,
const char *name, struct lock_class_key *key);
void init_timer_on_stack_key(struct timer_list *timer, unsigned int flags,
const char *name, struct lock_class_key *key)
{
debug_object_init_on_stack(timer, &timer_debug_descr);
do_init_timer(timer, flags, name, key);
}
EXPORT_SYMBOL_GPL(init_timer_on_stack_key);
void destroy_timer_on_stack(struct timer_list *timer)
{
debug_object_free(timer, &timer_debug_descr);
}
EXPORT_SYMBOL_GPL(destroy_timer_on_stack);
#else
static inline void debug_timer_init(struct timer_list *timer) { }
static inline void debug_timer_activate(struct timer_list *timer) { }
static inline void debug_timer_deactivate(struct timer_list *timer) { }
static inline void debug_timer_assert_init(struct timer_list *timer) { }
#endif
static inline void debug_init(struct timer_list *timer)
{
debug_timer_init(timer);
trace_timer_init(timer);
}
static inline void
debug_activate(struct timer_list *timer, unsigned long expires)
{
debug_timer_activate(timer);
trace_timer_start(timer, expires, timer->flags);
}
static inline void debug_deactivate(struct timer_list *timer)
{
debug_timer_deactivate(timer);
trace_timer_cancel(timer);
}
static inline void debug_assert_init(struct timer_list *timer)
{
debug_timer_assert_init(timer);
}
static void do_init_timer(struct timer_list *timer, unsigned int flags,
const char *name, struct lock_class_key *key)
{
timer->entry.pprev = NULL;
timer->flags = flags | raw_smp_processor_id();
timer->slack = -1;
#ifdef CONFIG_TIMER_STATS
timer->start_site = NULL;
timer->start_pid = -1;
memset(timer->start_comm, 0, TASK_COMM_LEN);
#endif
lockdep_init_map(&timer->lockdep_map, name, key, 0);
}
/**
* init_timer_key - initialize a timer
* @timer: the timer to be initialized
* @flags: timer flags
* @name: name of the timer
* @key: lockdep class key of the fake lock used for tracking timer
* sync lock dependencies
*
* init_timer_key() must be done to a timer prior calling *any* of the
* other timer functions.
*/
void init_timer_key(struct timer_list *timer, unsigned int flags,
const char *name, struct lock_class_key *key)
{
debug_init(timer);
do_init_timer(timer, flags, name, key);
}
EXPORT_SYMBOL(init_timer_key);
static inline void detach_timer(struct timer_list *timer, bool clear_pending)
{
struct hlist_node *entry = &timer->entry;
debug_deactivate(timer);
__hlist_del(entry);
if (clear_pending)
entry->pprev = NULL;
entry->next = LIST_POISON2;
}
static inline void
detach_expired_timer(struct timer_list *timer, struct tvec_base *base)
{
detach_timer(timer, true);
if (!(timer->flags & TIMER_DEFERRABLE))
base->active_timers--;
base->all_timers--;
}
static int detach_if_pending(struct timer_list *timer, struct tvec_base *base,
bool clear_pending)
{
if (!timer_pending(timer))
return 0;
detach_timer(timer, clear_pending);
if (!(timer->flags & TIMER_DEFERRABLE)) {
base->active_timers--;
if (timer->expires == base->next_timer)
base->next_timer = base->timer_jiffies;
}
/* If this was the last timer, advance base->jiffies */
if (!--base->all_timers)
base->timer_jiffies = jiffies;
return 1;
}
/*
* We are using hashed locking: holding per_cpu(tvec_bases).lock
* means that all timers which are tied to this base via timer->base are
* locked, and the base itself is locked too.
*
* So __run_timers/migrate_timers can safely modify all timers which could
* be found on ->tvX lists.
*
* When the timer's base is locked and removed from the list, the
* TIMER_MIGRATING flag is set, FIXME
*/
static struct tvec_base *lock_timer_base(struct timer_list *timer,
unsigned long *flags)
__acquires(timer->base->lock)
{
for (;;) {
u32 tf = timer->flags;
struct tvec_base *base;
if (!(tf & TIMER_MIGRATING)) {
base = per_cpu_ptr(&tvec_bases, tf & TIMER_CPUMASK);
spin_lock_irqsave(&base->lock, *flags);
if (timer->flags == tf)
return base;
spin_unlock_irqrestore(&base->lock, *flags);
}
cpu_relax();
}
}
static inline int
__mod_timer(struct timer_list *timer, unsigned long expires,
bool pending_only, int pinned)
{
struct tvec_base *base, *new_base;
unsigned long flags;
int ret = 0;
timer_stats_timer_set_start_info(timer);
BUG_ON(!timer->function);
base = lock_timer_base(timer, &flags);
ret = detach_if_pending(timer, base, false);
if (!ret && pending_only)
goto out_unlock;
debug_activate(timer, expires);
new_base = get_target_base(base, pinned);
if (base != new_base) {
/*
* We are trying to schedule the timer on the local CPU.
* However we can't change timer's base while it is running,
* otherwise del_timer_sync() can't detect that the timer's
* handler yet has not finished. This also guarantees that
* the timer is serialized wrt itself.
*/
if (likely(base->running_timer != timer)) {
/* See the comment in lock_timer_base() */
timer->flags |= TIMER_MIGRATING;
spin_unlock(&base->lock);
base = new_base;
spin_lock(&base->lock);
WRITE_ONCE(timer->flags,
(timer->flags & ~TIMER_BASEMASK) | base->cpu);
}
}
timer->expires = expires;
internal_add_timer(base, timer);
out_unlock:
spin_unlock_irqrestore(&base->lock, flags);
return ret;
}
/**
* mod_timer_pending - modify a pending timer's timeout
* @timer: the pending timer to be modified
* @expires: new timeout in jiffies
*
* mod_timer_pending() is the same for pending timers as mod_timer(),
* but will not re-activate and modify already deleted timers.
*
* It is useful for unserialized use of timers.
*/
int mod_timer_pending(struct timer_list *timer, unsigned long expires)
{
return __mod_timer(timer, expires, true, TIMER_NOT_PINNED);
}
EXPORT_SYMBOL(mod_timer_pending);
/*
* Decide where to put the timer while taking the slack into account
*
* Algorithm:
* 1) calculate the maximum (absolute) time
* 2) calculate the highest bit where the expires and new max are different
* 3) use this bit to make a mask
* 4) use the bitmask to round down the maximum time, so that all last
* bits are zeros
*/
static inline
unsigned long apply_slack(struct timer_list *timer, unsigned long expires)
{
unsigned long expires_limit, mask;
int bit;
if (timer->slack >= 0) {
expires_limit = expires + timer->slack;
} else {
long delta = expires - jiffies;
if (delta < 256)
return expires;
expires_limit = expires + delta / 256;
}
mask = expires ^ expires_limit;
if (mask == 0)
return expires;
bit = __fls(mask);
mask = (1UL << bit) - 1;
expires_limit = expires_limit & ~(mask);
return expires_limit;
}
/**
* mod_timer - modify a timer's timeout
* @timer: the timer to be modified
* @expires: new timeout in jiffies
*
* mod_timer() is a more efficient way to update the expire field of an
* active timer (if the timer is inactive it will be activated)
*
* mod_timer(timer, expires) is equivalent to:
*
* del_timer(timer); timer->expires = expires; add_timer(timer);
*
* Note that if there are multiple unserialized concurrent users of the
* same timer, then mod_timer() is the only safe way to modify the timeout,
* since add_timer() cannot modify an already running timer.
*
* The function returns whether it has modified a pending timer or not.
* (ie. mod_timer() of an inactive timer returns 0, mod_timer() of an
* active timer returns 1.)
*/
int mod_timer(struct timer_list *timer, unsigned long expires)
{
expires = apply_slack(timer, expires);
/*
* This is a common optimization triggered by the
* networking code - if the timer is re-modified
* to be the same thing then just return:
*/
if (timer_pending(timer) && timer->expires == expires)
return 1;
return __mod_timer(timer, expires, false, TIMER_NOT_PINNED);
}
EXPORT_SYMBOL(mod_timer);
/**
* mod_timer_pinned - modify a timer's timeout
* @timer: the timer to be modified
* @expires: new timeout in jiffies
*
* mod_timer_pinned() is a way to update the expire field of an
* active timer (if the timer is inactive it will be activated)
* and to ensure that the timer is scheduled on the current CPU.
*
* Note that this does not prevent the timer from being migrated
* when the current CPU goes offline. If this is a problem for
* you, use CPU-hotplug notifiers to handle it correctly, for
* example, cancelling the timer when the corresponding CPU goes
* offline.
*
* mod_timer_pinned(timer, expires) is equivalent to:
*
* del_timer(timer); timer->expires = expires; add_timer(timer);
*/
int mod_timer_pinned(struct timer_list *timer, unsigned long expires)
{
if (timer->expires == expires && timer_pending(timer))
return 1;
return __mod_timer(timer, expires, false, TIMER_PINNED);
}
EXPORT_SYMBOL(mod_timer_pinned);
/**
* add_timer - start a timer
* @timer: the timer to be added
*
* The kernel will do a ->function(->data) callback from the
* timer interrupt at the ->expires point in the future. The
* current time is 'jiffies'.
*
* The timer's ->expires, ->function (and if the handler uses it, ->data)
* fields must be set prior calling this function.
*
* Timers with an ->expires field in the past will be executed in the next
* timer tick.
*/
void add_timer(struct timer_list *timer)
{
BUG_ON(timer_pending(timer));
mod_timer(timer, timer->expires);
}
EXPORT_SYMBOL(add_timer);
/**
* add_timer_on - start a timer on a particular CPU
* @timer: the timer to be added
* @cpu: the CPU to start it on
*
* This is not very scalable on SMP. Double adds are not possible.
*/
void add_timer_on(struct timer_list *timer, int cpu)
{
struct tvec_base *new_base = per_cpu_ptr(&tvec_bases, cpu);
struct tvec_base *base;
unsigned long flags;
timer_stats_timer_set_start_info(timer);
BUG_ON(timer_pending(timer) || !timer->function);
/*
* If @timer was on a different CPU, it should be migrated with the
* old base locked to prevent other operations proceeding with the
* wrong base locked. See lock_timer_base().
*/
base = lock_timer_base(timer, &flags);
if (base != new_base) {
timer->flags |= TIMER_MIGRATING;
spin_unlock(&base->lock);
base = new_base;
spin_lock(&base->lock);
WRITE_ONCE(timer->flags,
(timer->flags & ~TIMER_BASEMASK) | cpu);
}
debug_activate(timer, timer->expires);
internal_add_timer(base, timer);
spin_unlock_irqrestore(&base->lock, flags);
}
EXPORT_SYMBOL_GPL(add_timer_on);
/**
* del_timer - deactive a timer.
* @timer: the timer to be deactivated
*
* del_timer() deactivates a timer - this works on both active and inactive
* timers.
*
* The function returns whether it has deactivated a pending timer or not.
* (ie. del_timer() of an inactive timer returns 0, del_timer() of an
* active timer returns 1.)
*/
int del_timer(struct timer_list *timer)
{
struct tvec_base *base;
unsigned long flags;
int ret = 0;
debug_assert_init(timer);
timer_stats_timer_clear_start_info(timer);
if (timer_pending(timer)) {
base = lock_timer_base(timer, &flags);
ret = detach_if_pending(timer, base, true);
spin_unlock_irqrestore(&base->lock, flags);
}
return ret;
}
EXPORT_SYMBOL(del_timer);
/**
* try_to_del_timer_sync - Try to deactivate a timer
* @timer: timer do del
*
* This function tries to deactivate a timer. Upon successful (ret >= 0)
* exit the timer is not queued and the handler is not running on any CPU.
*/
int try_to_del_timer_sync(struct timer_list *timer)
{
struct tvec_base *base;
unsigned long flags;
int ret = -1;
debug_assert_init(timer);
base = lock_timer_base(timer, &flags);
if (base->running_timer != timer) {
timer_stats_timer_clear_start_info(timer);
ret = detach_if_pending(timer, base, true);
}
spin_unlock_irqrestore(&base->lock, flags);
return ret;
}
EXPORT_SYMBOL(try_to_del_timer_sync);
#ifdef CONFIG_SMP
/**
* del_timer_sync - deactivate a timer and wait for the handler to finish.
* @timer: the timer to be deactivated
*
* This function only differs from del_timer() on SMP: besides deactivating
* the timer it also makes sure the handler has finished executing on other
* CPUs.
*
* Synchronization rules: Callers must prevent restarting of the timer,
* otherwise this function is meaningless. It must not be called from
* interrupt contexts unless the timer is an irqsafe one. The caller must
* not hold locks which would prevent completion of the timer's
* handler. The timer's handler must not call add_timer_on(). Upon exit the
* timer is not queued and the handler is not running on any CPU.
*
* Note: For !irqsafe timers, you must not hold locks that are held in
* interrupt context while calling this function. Even if the lock has
* nothing to do with the timer in question. Here's why:
*
* CPU0 CPU1
* ---- ----
* <SOFTIRQ>
* call_timer_fn();
* base->running_timer = mytimer;
* spin_lock_irq(somelock);
* <IRQ>
* spin_lock(somelock);
* del_timer_sync(mytimer);
* while (base->running_timer == mytimer);
*
* Now del_timer_sync() will never return and never release somelock.
* The interrupt on the other CPU is waiting to grab somelock but
* it has interrupted the softirq that CPU0 is waiting to finish.
*
* The function returns whether it has deactivated a pending timer or not.
*/
int del_timer_sync(struct timer_list *timer)
{
#ifdef CONFIG_LOCKDEP
unsigned long flags;
/*
* If lockdep gives a backtrace here, please reference
* the synchronization rules above.
*/
local_irq_save(flags);
lock_map_acquire(&timer->lockdep_map);
lock_map_release(&timer->lockdep_map);
local_irq_restore(flags);
#endif
/*
* don't use it in hardirq context, because it
* could lead to deadlock.
*/
WARN_ON(in_irq() && !(timer->flags & TIMER_IRQSAFE));
for (;;) {
int ret = try_to_del_timer_sync(timer);
if (ret >= 0)
return ret;
cpu_relax();
}
}
EXPORT_SYMBOL(del_timer_sync);
#endif
static int cascade(struct tvec_base *base, struct tvec *tv, int index)
{
/* cascade all the timers from tv up one level */
struct timer_list *timer;
struct hlist_node *tmp;
struct hlist_head tv_list;
hlist_move_list(tv->vec + index, &tv_list);
/*
* We are removing _all_ timers from the list, so we
* don't have to detach them individually.
*/
hlist_for_each_entry_safe(timer, tmp, &tv_list, entry) {
/* No accounting, while moving them */
__internal_add_timer(base, timer);
}
return index;
}
static void call_timer_fn(struct timer_list *timer, void (*fn)(unsigned long),
unsigned long data)
{
int count = preempt_count();
#ifdef CONFIG_LOCKDEP
/*
* It is permissible to free the timer from inside the
* function that is called from it, this we need to take into
* account for lockdep too. To avoid bogus "held lock freed"
* warnings as well as problems when looking into
* timer->lockdep_map, make a copy and use that here.
*/
struct lockdep_map lockdep_map;
lockdep_copy_map(&lockdep_map, &timer->lockdep_map);
#endif
/*
* Couple the lock chain with the lock chain at
* del_timer_sync() by acquiring the lock_map around the fn()
* call here and in del_timer_sync().
*/
lock_map_acquire(&lockdep_map);
trace_timer_expire_entry(timer);
fn(data);
trace_timer_expire_exit(timer);
lock_map_release(&lockdep_map);
if (count != preempt_count()) {
WARN_ONCE(1, "timer: %pF preempt leak: %08x -> %08x\n",
fn, count, preempt_count());
/*
* Restore the preempt count. That gives us a decent
* chance to survive and extract information. If the
* callback kept a lock held, bad luck, but not worse
* than the BUG() we had.
*/
preempt_count_set(count);
}
}
#define INDEX(N) ((base->timer_jiffies >> (TVR_BITS + (N) * TVN_BITS)) & TVN_MASK)
/**
* __run_timers - run all expired timers (if any) on this CPU.
* @base: the timer vector to be processed.
*
* This function cascades all vectors and executes all expired timer
* vectors.
*/
static inline void __run_timers(struct tvec_base *base)
{
struct timer_list *timer;
spin_lock_irq(&base->lock);
while (time_after_eq(jiffies, base->timer_jiffies)) {
struct hlist_head work_list;
struct hlist_head *head = &work_list;
int index;
if (!base->all_timers) {
base->timer_jiffies = jiffies;
break;
}
index = base->timer_jiffies & TVR_MASK;
/*
* Cascade timers:
*/
if (!index &&
(!cascade(base, &base->tv2, INDEX(0))) &&
(!cascade(base, &base->tv3, INDEX(1))) &&
!cascade(base, &base->tv4, INDEX(2)))
cascade(base, &base->tv5, INDEX(3));
++base->timer_jiffies;
hlist_move_list(base->tv1.vec + index, head);
while (!hlist_empty(head)) {
void (*fn)(unsigned long);
unsigned long data;
bool irqsafe;
timer = hlist_entry(head->first, struct timer_list, entry);
fn = timer->function;
data = timer->data;
irqsafe = timer->flags & TIMER_IRQSAFE;
timer_stats_account_timer(timer);
base->running_timer = timer;
detach_expired_timer(timer, base);
if (irqsafe) {
spin_unlock(&base->lock);
call_timer_fn(timer, fn, data);
spin_lock(&base->lock);
} else {
spin_unlock_irq(&base->lock);
call_timer_fn(timer, fn, data);
spin_lock_irq(&base->lock);
}
}
}
base->running_timer = NULL;
spin_unlock_irq(&base->lock);
}
#ifdef CONFIG_NO_HZ_COMMON
/*
* Find out when the next timer event is due to happen. This
* is used on S/390 to stop all activity when a CPU is idle.
* This function needs to be called with interrupts disabled.
*/
static unsigned long __next_timer_interrupt(struct tvec_base *base)
{
unsigned long timer_jiffies = base->timer_jiffies;
unsigned long expires = timer_jiffies + NEXT_TIMER_MAX_DELTA;
int index, slot, array, found = 0;
struct timer_list *nte;
struct tvec *varray[4];
/* Look for timer events in tv1. */
index = slot = timer_jiffies & TVR_MASK;
do {
hlist_for_each_entry(nte, base->tv1.vec + slot, entry) {
if (nte->flags & TIMER_DEFERRABLE)
continue;
found = 1;
expires = nte->expires;
/* Look at the cascade bucket(s)? */
if (!index || slot < index)
goto cascade;
return expires;
}
slot = (slot + 1) & TVR_MASK;
} while (slot != index);
cascade:
/* Calculate the next cascade event */
if (index)
timer_jiffies += TVR_SIZE - index;
timer_jiffies >>= TVR_BITS;
/* Check tv2-tv5. */
varray[0] = &base->tv2;
varray[1] = &base->tv3;
varray[2] = &base->tv4;
varray[3] = &base->tv5;
for (array = 0; array < 4; array++) {
struct tvec *varp = varray[array];
index = slot = timer_jiffies & TVN_MASK;
do {
hlist_for_each_entry(nte, varp->vec + slot, entry) {
if (nte->flags & TIMER_DEFERRABLE)
continue;
found = 1;
if (time_before(nte->expires, expires))
expires = nte->expires;
}
/*
* Do we still search for the first timer or are
* we looking up the cascade buckets ?
*/
if (found) {
/* Look at the cascade bucket(s)? */
if (!index || slot < index)
break;
return expires;
}
slot = (slot + 1) & TVN_MASK;
} while (slot != index);
if (index)
timer_jiffies += TVN_SIZE - index;
timer_jiffies >>= TVN_BITS;
}
return expires;
}
/*
* Check, if the next hrtimer event is before the next timer wheel
* event:
*/
static u64 cmp_next_hrtimer_event(u64 basem, u64 expires)
{
u64 nextevt = hrtimer_get_next_event();
/*
* If high resolution timers are enabled
* hrtimer_get_next_event() returns KTIME_MAX.
*/
if (expires <= nextevt)
return expires;
/*
* If the next timer is already expired, return the tick base
* time so the tick is fired immediately.
*/
if (nextevt <= basem)
return basem;
/*
* Round up to the next jiffie. High resolution timers are
* off, so the hrtimers are expired in the tick and we need to
* make sure that this tick really expires the timer to avoid
* a ping pong of the nohz stop code.
*
* Use DIV_ROUND_UP_ULL to prevent gcc calling __divdi3
*/
return DIV_ROUND_UP_ULL(nextevt, TICK_NSEC) * TICK_NSEC;
}
/**
* get_next_timer_interrupt - return the time (clock mono) of the next timer
* @basej: base time jiffies
* @basem: base time clock monotonic
*
* Returns the tick aligned clock monotonic time of the next pending
* timer or KTIME_MAX if no timer is pending.
*/
u64 get_next_timer_interrupt(unsigned long basej, u64 basem)
{
struct tvec_base *base = this_cpu_ptr(&tvec_bases);
u64 expires = KTIME_MAX;
unsigned long nextevt;
/*
* Pretend that there is no timer pending if the cpu is offline.
* Possible pending timers will be migrated later to an active cpu.
*/
if (cpu_is_offline(smp_processor_id()))
return expires;
spin_lock(&base->lock);
if (base->active_timers) {
if (time_before_eq(base->next_timer, base->timer_jiffies))
base->next_timer = __next_timer_interrupt(base);
nextevt = base->next_timer;
if (time_before_eq(nextevt, basej))
expires = basem;
else
expires = basem + (nextevt - basej) * TICK_NSEC;
}
spin_unlock(&base->lock);
return cmp_next_hrtimer_event(basem, expires);
}
#endif
/*
* Called from the timer interrupt handler to charge one tick to the current
* process. user_tick is 1 if the tick is user time, 0 for system.
*/
void update_process_times(int user_tick)
{
struct task_struct *p = current;
/* Note: this timer irq context must be accounted for as well. */
account_process_tick(p, user_tick);
run_local_timers();
rcu_check_callbacks(user_tick);
#ifdef CONFIG_IRQ_WORK
if (in_irq())
irq_work_tick();
#endif
scheduler_tick();
run_posix_cpu_timers(p);
}
/*
* This function runs timers and the timer-tq in bottom half context.
*/
static void run_timer_softirq(struct softirq_action *h)
{
struct tvec_base *base = this_cpu_ptr(&tvec_bases);
if (time_after_eq(jiffies, base->timer_jiffies))
__run_timers(base);
}
/*
* Called by the local, per-CPU timer interrupt on SMP.
*/
void run_local_timers(void)
{
hrtimer_run_queues();
raise_softirq(TIMER_SOFTIRQ);
}
#ifdef __ARCH_WANT_SYS_ALARM
/*
* For backwards compatibility? This can be done in libc so Alpha
* and all newer ports shouldn't need it.
*/
SYSCALL_DEFINE1(alarm, unsigned int, seconds)
{
return alarm_setitimer(seconds);
}
#endif
static void process_timeout(unsigned long __data)
{
wake_up_process((struct task_struct *)__data);
}
/**
* schedule_timeout - sleep until timeout
* @timeout: timeout value in jiffies
*
* Make the current task sleep until @timeout jiffies have
* elapsed. The routine will return immediately unless
* the current task state has been set (see set_current_state()).
*
* You can set the task state as follows -
*
* %TASK_UNINTERRUPTIBLE - at least @timeout jiffies are guaranteed to
* pass before the routine returns. The routine will return 0
*
* %TASK_INTERRUPTIBLE - the routine may return early if a signal is
* delivered to the current task. In this case the remaining time
* in jiffies will be returned, or 0 if the timer expired in time
*
* The current task state is guaranteed to be TASK_RUNNING when this
* routine returns.
*
* Specifying a @timeout value of %MAX_SCHEDULE_TIMEOUT will schedule
* the CPU away without a bound on the timeout. In this case the return
* value will be %MAX_SCHEDULE_TIMEOUT.
*
* In all cases the return value is guaranteed to be non-negative.
*/
signed long __sched schedule_timeout(signed long timeout)
{
struct timer_list timer;
unsigned long expire;
switch (timeout)
{
case MAX_SCHEDULE_TIMEOUT:
/*
* These two special cases are useful to be comfortable
* in the caller. Nothing more. We could take
* MAX_SCHEDULE_TIMEOUT from one of the negative value
* but I' d like to return a valid offset (>=0) to allow
* the caller to do everything it want with the retval.
*/
schedule();
goto out;
default:
/*
* Another bit of PARANOID. Note that the retval will be
* 0 since no piece of kernel is supposed to do a check
* for a negative retval of schedule_timeout() (since it
* should never happens anyway). You just have the printk()
* that will tell you if something is gone wrong and where.
*/
if (timeout < 0) {
printk(KERN_ERR "schedule_timeout: wrong timeout "
"value %lx\n", timeout);
dump_stack();
current->state = TASK_RUNNING;
goto out;
}
}
expire = timeout + jiffies;
setup_timer_on_stack(&timer, process_timeout, (unsigned long)current);
__mod_timer(&timer, expire, false, TIMER_NOT_PINNED);
schedule();
del_singleshot_timer_sync(&timer);
/* Remove the timer from the object tracker */
destroy_timer_on_stack(&timer);
timeout = expire - jiffies;
out:
return timeout < 0 ? 0 : timeout;
}
EXPORT_SYMBOL(schedule_timeout);
/*
* We can use __set_current_state() here because schedule_timeout() calls
* schedule() unconditionally.
*/
signed long __sched schedule_timeout_interruptible(signed long timeout)
{
__set_current_state(TASK_INTERRUPTIBLE);
return schedule_timeout(timeout);
}
EXPORT_SYMBOL(schedule_timeout_interruptible);
signed long __sched schedule_timeout_killable(signed long timeout)
{
__set_current_state(TASK_KILLABLE);
return schedule_timeout(timeout);
}
EXPORT_SYMBOL(schedule_timeout_killable);
signed long __sched schedule_timeout_uninterruptible(signed long timeout)
{
__set_current_state(TASK_UNINTERRUPTIBLE);
return schedule_timeout(timeout);
}
EXPORT_SYMBOL(schedule_timeout_uninterruptible);
#ifdef CONFIG_HOTPLUG_CPU
static void migrate_timer_list(struct tvec_base *new_base, struct hlist_head *head)
{
struct timer_list *timer;
int cpu = new_base->cpu;
while (!hlist_empty(head)) {
timer = hlist_entry(head->first, struct timer_list, entry);
/* We ignore the accounting on the dying cpu */
detach_timer(timer, false);
timer->flags = (timer->flags & ~TIMER_BASEMASK) | cpu;
internal_add_timer(new_base, timer);
}
}
static void migrate_timers(int cpu)
{
struct tvec_base *old_base;
struct tvec_base *new_base;
int i;
BUG_ON(cpu_online(cpu));
old_base = per_cpu_ptr(&tvec_bases, cpu);
new_base = get_cpu_ptr(&tvec_bases);
/*
* The caller is globally serialized and nobody else
* takes two locks at once, deadlock is not possible.
*/
spin_lock_irq(&new_base->lock);
spin_lock_nested(&old_base->lock, SINGLE_DEPTH_NESTING);
BUG_ON(old_base->running_timer);
for (i = 0; i < TVR_SIZE; i++)
migrate_timer_list(new_base, old_base->tv1.vec + i);
for (i = 0; i < TVN_SIZE; i++) {
migrate_timer_list(new_base, old_base->tv2.vec + i);
migrate_timer_list(new_base, old_base->tv3.vec + i);
migrate_timer_list(new_base, old_base->tv4.vec + i);
migrate_timer_list(new_base, old_base->tv5.vec + i);
}
old_base->active_timers = 0;
old_base->all_timers = 0;
spin_unlock(&old_base->lock);
spin_unlock_irq(&new_base->lock);
put_cpu_ptr(&tvec_bases);
}
static int timer_cpu_notify(struct notifier_block *self,
unsigned long action, void *hcpu)
{
switch (action) {
case CPU_DEAD:
case CPU_DEAD_FROZEN:
migrate_timers((long)hcpu);
break;
default:
break;
}
return NOTIFY_OK;
}
static inline void timer_register_cpu_notifier(void)
{
cpu_notifier(timer_cpu_notify, 0);
}
#else
static inline void timer_register_cpu_notifier(void) { }
#endif /* CONFIG_HOTPLUG_CPU */
static void __init init_timer_cpu(int cpu)
{
struct tvec_base *base = per_cpu_ptr(&tvec_bases, cpu);
base->cpu = cpu;
spin_lock_init(&base->lock);
base->timer_jiffies = jiffies;
base->next_timer = base->timer_jiffies;
}
static void __init init_timer_cpus(void)
{
int cpu;
for_each_possible_cpu(cpu)
init_timer_cpu(cpu);
}
void __init init_timers(void)
{
init_timer_cpus();
init_timer_stats();
timer_register_cpu_notifier();
open_softirq(TIMER_SOFTIRQ, run_timer_softirq);
}
/**
* msleep - sleep safely even with waitqueue interruptions
* @msecs: Time in milliseconds to sleep for
*/
void msleep(unsigned int msecs)
{
unsigned long timeout = msecs_to_jiffies(msecs) + 1;
while (timeout)
timeout = schedule_timeout_uninterruptible(timeout);
}
EXPORT_SYMBOL(msleep);
/**
* msleep_interruptible - sleep waiting for signals
* @msecs: Time in milliseconds to sleep for
*/
unsigned long msleep_interruptible(unsigned int msecs)
{
unsigned long timeout = msecs_to_jiffies(msecs) + 1;
while (timeout && !signal_pending(current))
timeout = schedule_timeout_interruptible(timeout);
return jiffies_to_msecs(timeout);
}
EXPORT_SYMBOL(msleep_interruptible);
static void __sched do_usleep_range(unsigned long min, unsigned long max)
{
ktime_t kmin;
unsigned long delta;
kmin = ktime_set(0, min * NSEC_PER_USEC);
delta = (max - min) * NSEC_PER_USEC;
schedule_hrtimeout_range(&kmin, delta, HRTIMER_MODE_REL);
}
/**
* usleep_range - Drop in replacement for udelay where wakeup is flexible
* @min: Minimum time in usecs to sleep
* @max: Maximum time in usecs to sleep
*/
void __sched usleep_range(unsigned long min, unsigned long max)
{
__set_current_state(TASK_UNINTERRUPTIBLE);
do_usleep_range(min, max);
}
EXPORT_SYMBOL(usleep_range);