linux/kernel/time/timer.c
Anna-Maria Gleixner 14c803419d hrtimer: Unify remote enqueue handling
hrtimer_reprogram() is conditionally invoked from hrtimer_start_range_ns()
when hrtimer_cpu_base.hres_active is true.

In the !hres_active case there is a special condition for the nohz_active
case:

  If the newly enqueued timer expires before the first expiring timer on a
  remote CPU then the remote CPU needs to be notified and woken up from a
  NOHZ idle sleep to take the new first expiring timer into account.

Previous changes have already established the prerequisites to make the
remote enqueue behaviour the same whether high resolution mode is active or
not:

  If the to be enqueued timer expires before the first expiring timer on a
  remote CPU, then it cannot be enqueued there.

This was done for the high resolution mode because there is no way to
access the remote CPU timer hardware. The same is true for NOHZ, but was
handled differently by unconditionally enqueuing the timer and waking up
the remote CPU so it can reprogram its timer. Again there is no compelling
reason for this difference.

hrtimer_check_target(), which makes the 'can remote enqueue' decision is
already unconditional, but not yet functional because nothing updates
hrtimer_cpu_base.expires_next in the !hres_active case.

To unify this the following changes are required:

 1) Make the store of the new first expiry time unconditonal in
    hrtimer_reprogram() and check __hrtimer_hres_active() before proceeding
    to the actual hardware access. This check also lets the compiler
    eliminate the rest of the function in case of CONFIG_HIGH_RES_TIMERS=n.

 2) Invoke hrtimer_reprogram() unconditionally from
    hrtimer_start_range_ns()

 3) Remove the remote wakeup special case for the !high_res && nohz_active
    case.

Confine the timers_nohz_active static key to timer.c which is the only user
now.

Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
Cc: Christoph Hellwig <hch@lst.de>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: keescook@chromium.org
Link: http://lkml.kernel.org/r/20171221104205.7269-21-anna-maria@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2018-01-16 02:53:58 +01:00

1991 lines
57 KiB
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/signal.h>
#include <linux/sched/sysctl.h>
#include <linux/sched/nohz.h>
#include <linux/sched/debug.h>
#include <linux/slab.h>
#include <linux/compat.h>
#include <linux/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);
/*
* The timer wheel has LVL_DEPTH array levels. Each level provides an array of
* LVL_SIZE buckets. Each level is driven by its own clock and therefor each
* level has a different granularity.
*
* The level granularity is: LVL_CLK_DIV ^ lvl
* The level clock frequency is: HZ / (LVL_CLK_DIV ^ level)
*
* The array level of a newly armed timer depends on the relative expiry
* time. The farther the expiry time is away the higher the array level and
* therefor the granularity becomes.
*
* Contrary to the original timer wheel implementation, which aims for 'exact'
* expiry of the timers, this implementation removes the need for recascading
* the timers into the lower array levels. The previous 'classic' timer wheel
* implementation of the kernel already violated the 'exact' expiry by adding
* slack to the expiry time to provide batched expiration. The granularity
* levels provide implicit batching.
*
* This is an optimization of the original timer wheel implementation for the
* majority of the timer wheel use cases: timeouts. The vast majority of
* timeout timers (networking, disk I/O ...) are canceled before expiry. If
* the timeout expires it indicates that normal operation is disturbed, so it
* does not matter much whether the timeout comes with a slight delay.
*
* The only exception to this are networking timers with a small expiry
* time. They rely on the granularity. Those fit into the first wheel level,
* which has HZ granularity.
*
* We don't have cascading anymore. timers with a expiry time above the
* capacity of the last wheel level are force expired at the maximum timeout
* value of the last wheel level. From data sampling we know that the maximum
* value observed is 5 days (network connection tracking), so this should not
* be an issue.
*
* The currently chosen array constants values are a good compromise between
* array size and granularity.
*
* This results in the following granularity and range levels:
*
* HZ 1000 steps
* Level Offset Granularity Range
* 0 0 1 ms 0 ms - 63 ms
* 1 64 8 ms 64 ms - 511 ms
* 2 128 64 ms 512 ms - 4095 ms (512ms - ~4s)
* 3 192 512 ms 4096 ms - 32767 ms (~4s - ~32s)
* 4 256 4096 ms (~4s) 32768 ms - 262143 ms (~32s - ~4m)
* 5 320 32768 ms (~32s) 262144 ms - 2097151 ms (~4m - ~34m)
* 6 384 262144 ms (~4m) 2097152 ms - 16777215 ms (~34m - ~4h)
* 7 448 2097152 ms (~34m) 16777216 ms - 134217727 ms (~4h - ~1d)
* 8 512 16777216 ms (~4h) 134217728 ms - 1073741822 ms (~1d - ~12d)
*
* HZ 300
* Level Offset Granularity Range
* 0 0 3 ms 0 ms - 210 ms
* 1 64 26 ms 213 ms - 1703 ms (213ms - ~1s)
* 2 128 213 ms 1706 ms - 13650 ms (~1s - ~13s)
* 3 192 1706 ms (~1s) 13653 ms - 109223 ms (~13s - ~1m)
* 4 256 13653 ms (~13s) 109226 ms - 873810 ms (~1m - ~14m)
* 5 320 109226 ms (~1m) 873813 ms - 6990503 ms (~14m - ~1h)
* 6 384 873813 ms (~14m) 6990506 ms - 55924050 ms (~1h - ~15h)
* 7 448 6990506 ms (~1h) 55924053 ms - 447392423 ms (~15h - ~5d)
* 8 512 55924053 ms (~15h) 447392426 ms - 3579139406 ms (~5d - ~41d)
*
* HZ 250
* Level Offset Granularity Range
* 0 0 4 ms 0 ms - 255 ms
* 1 64 32 ms 256 ms - 2047 ms (256ms - ~2s)
* 2 128 256 ms 2048 ms - 16383 ms (~2s - ~16s)
* 3 192 2048 ms (~2s) 16384 ms - 131071 ms (~16s - ~2m)
* 4 256 16384 ms (~16s) 131072 ms - 1048575 ms (~2m - ~17m)
* 5 320 131072 ms (~2m) 1048576 ms - 8388607 ms (~17m - ~2h)
* 6 384 1048576 ms (~17m) 8388608 ms - 67108863 ms (~2h - ~18h)
* 7 448 8388608 ms (~2h) 67108864 ms - 536870911 ms (~18h - ~6d)
* 8 512 67108864 ms (~18h) 536870912 ms - 4294967288 ms (~6d - ~49d)
*
* HZ 100
* Level Offset Granularity Range
* 0 0 10 ms 0 ms - 630 ms
* 1 64 80 ms 640 ms - 5110 ms (640ms - ~5s)
* 2 128 640 ms 5120 ms - 40950 ms (~5s - ~40s)
* 3 192 5120 ms (~5s) 40960 ms - 327670 ms (~40s - ~5m)
* 4 256 40960 ms (~40s) 327680 ms - 2621430 ms (~5m - ~43m)
* 5 320 327680 ms (~5m) 2621440 ms - 20971510 ms (~43m - ~5h)
* 6 384 2621440 ms (~43m) 20971520 ms - 167772150 ms (~5h - ~1d)
* 7 448 20971520 ms (~5h) 167772160 ms - 1342177270 ms (~1d - ~15d)
*/
/* Clock divisor for the next level */
#define LVL_CLK_SHIFT 3
#define LVL_CLK_DIV (1UL << LVL_CLK_SHIFT)
#define LVL_CLK_MASK (LVL_CLK_DIV - 1)
#define LVL_SHIFT(n) ((n) * LVL_CLK_SHIFT)
#define LVL_GRAN(n) (1UL << LVL_SHIFT(n))
/*
* The time start value for each level to select the bucket at enqueue
* time.
*/
#define LVL_START(n) ((LVL_SIZE - 1) << (((n) - 1) * LVL_CLK_SHIFT))
/* Size of each clock level */
#define LVL_BITS 6
#define LVL_SIZE (1UL << LVL_BITS)
#define LVL_MASK (LVL_SIZE - 1)
#define LVL_OFFS(n) ((n) * LVL_SIZE)
/* Level depth */
#if HZ > 100
# define LVL_DEPTH 9
# else
# define LVL_DEPTH 8
#endif
/* The cutoff (max. capacity of the wheel) */
#define WHEEL_TIMEOUT_CUTOFF (LVL_START(LVL_DEPTH))
#define WHEEL_TIMEOUT_MAX (WHEEL_TIMEOUT_CUTOFF - LVL_GRAN(LVL_DEPTH - 1))
/*
* The resulting wheel size. If NOHZ is configured we allocate two
* wheels so we have a separate storage for the deferrable timers.
*/
#define WHEEL_SIZE (LVL_SIZE * LVL_DEPTH)
#ifdef CONFIG_NO_HZ_COMMON
# define NR_BASES 2
# define BASE_STD 0
# define BASE_DEF 1
#else
# define NR_BASES 1
# define BASE_STD 0
# define BASE_DEF 0
#endif
struct timer_base {
raw_spinlock_t lock;
struct timer_list *running_timer;
unsigned long clk;
unsigned long next_expiry;
unsigned int cpu;
bool is_idle;
bool must_forward_clk;
DECLARE_BITMAP(pending_map, WHEEL_SIZE);
struct hlist_head vectors[WHEEL_SIZE];
} ____cacheline_aligned;
static DEFINE_PER_CPU(struct timer_base, timer_bases[NR_BASES]);
#ifdef CONFIG_NO_HZ_COMMON
static DEFINE_STATIC_KEY_FALSE(timers_nohz_active);
static DEFINE_MUTEX(timer_keys_mutex);
static void timer_update_keys(struct work_struct *work);
static DECLARE_WORK(timer_update_work, timer_update_keys);
#ifdef CONFIG_SMP
unsigned int sysctl_timer_migration = 1;
DEFINE_STATIC_KEY_FALSE(timers_migration_enabled);
static void timers_update_migration(void)
{
if (sysctl_timer_migration && tick_nohz_active)
static_branch_enable(&timers_migration_enabled);
else
static_branch_disable(&timers_migration_enabled);
}
#else
static inline void timers_update_migration(void) { }
#endif /* !CONFIG_SMP */
static void timer_update_keys(struct work_struct *work)
{
mutex_lock(&timer_keys_mutex);
timers_update_migration();
static_branch_enable(&timers_nohz_active);
mutex_unlock(&timer_keys_mutex);
}
void timers_update_nohz(void)
{
schedule_work(&timer_update_work);
}
int timer_migration_handler(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp,
loff_t *ppos)
{
int ret;
mutex_lock(&timer_keys_mutex);
ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
if (!ret && write)
timers_update_migration();
mutex_unlock(&timer_keys_mutex);
return ret;
}
static inline bool is_timers_nohz_active(void)
{
return static_branch_unlikely(&timers_nohz_active);
}
#else
static inline bool is_timers_nohz_active(void) { return false; }
#endif /* NO_HZ_COMMON */
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);
static inline unsigned int timer_get_idx(struct timer_list *timer)
{
return (timer->flags & TIMER_ARRAYMASK) >> TIMER_ARRAYSHIFT;
}
static inline void timer_set_idx(struct timer_list *timer, unsigned int idx)
{
timer->flags = (timer->flags & ~TIMER_ARRAYMASK) |
idx << TIMER_ARRAYSHIFT;
}
/*
* Helper function to calculate the array index for a given expiry
* time.
*/
static inline unsigned calc_index(unsigned expires, unsigned lvl)
{
expires = (expires + LVL_GRAN(lvl)) >> LVL_SHIFT(lvl);
return LVL_OFFS(lvl) + (expires & LVL_MASK);
}
static int calc_wheel_index(unsigned long expires, unsigned long clk)
{
unsigned long delta = expires - clk;
unsigned int idx;
if (delta < LVL_START(1)) {
idx = calc_index(expires, 0);
} else if (delta < LVL_START(2)) {
idx = calc_index(expires, 1);
} else if (delta < LVL_START(3)) {
idx = calc_index(expires, 2);
} else if (delta < LVL_START(4)) {
idx = calc_index(expires, 3);
} else if (delta < LVL_START(5)) {
idx = calc_index(expires, 4);
} else if (delta < LVL_START(6)) {
idx = calc_index(expires, 5);
} else if (delta < LVL_START(7)) {
idx = calc_index(expires, 6);
} else if (LVL_DEPTH > 8 && delta < LVL_START(8)) {
idx = calc_index(expires, 7);
} else if ((long) delta < 0) {
idx = clk & LVL_MASK;
} else {
/*
* Force expire obscene large timeouts to expire at the
* capacity limit of the wheel.
*/
if (expires >= WHEEL_TIMEOUT_CUTOFF)
expires = WHEEL_TIMEOUT_MAX;
idx = calc_index(expires, LVL_DEPTH - 1);
}
return idx;
}
/*
* Enqueue the timer into the hash bucket, mark it pending in
* the bitmap and store the index in the timer flags.
*/
static void enqueue_timer(struct timer_base *base, struct timer_list *timer,
unsigned int idx)
{
hlist_add_head(&timer->entry, base->vectors + idx);
__set_bit(idx, base->pending_map);
timer_set_idx(timer, idx);
}
static void
__internal_add_timer(struct timer_base *base, struct timer_list *timer)
{
unsigned int idx;
idx = calc_wheel_index(timer->expires, base->clk);
enqueue_timer(base, timer, idx);
}
static void
trigger_dyntick_cpu(struct timer_base *base, struct timer_list *timer)
{
if (!is_timers_nohz_active())
return;
/*
* TODO: This wants some optimizing similar to the code below, but we
* will do that when we switch from push to pull for deferrable timers.
*/
if (timer->flags & TIMER_DEFERRABLE) {
if (tick_nohz_full_cpu(base->cpu))
wake_up_nohz_cpu(base->cpu);
return;
}
/*
* We might have to IPI the remote CPU if the base is idle and the
* timer is not deferrable. If the other CPU is on the way to idle
* then it can't set base->is_idle as we hold the base lock:
*/
if (!base->is_idle)
return;
/* Check whether this is the new first expiring timer: */
if (time_after_eq(timer->expires, base->next_expiry))
return;
/*
* Set the next expiry time and kick the CPU so it can reevaluate the
* wheel:
*/
base->next_expiry = timer->expires;
wake_up_nohz_cpu(base->cpu);
}
static void
internal_add_timer(struct timer_base *base, struct timer_list *timer)
{
__internal_add_timer(base, timer);
trigger_dyntick_cpu(base, timer);
}
#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;
}
static bool timer_is_static_object(void *addr)
{
struct timer_list *timer = addr;
return (timer->entry.pprev == NULL &&
timer->entry.next == TIMER_ENTRY_STATIC);
}
/*
* fixup_init is called when:
* - an active object is initialized
*/
static bool 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 true;
default:
return false;
}
}
/* Stub timer callback for improperly used timers. */
static void stub_timer(struct timer_list *unused)
{
WARN_ON(1);
}
/*
* fixup_activate is called when:
* - an active object is activated
* - an unknown non-static object is activated
*/
static bool timer_fixup_activate(void *addr, enum debug_obj_state state)
{
struct timer_list *timer = addr;
switch (state) {
case ODEBUG_STATE_NOTAVAILABLE:
timer_setup(timer, stub_timer, 0);
return true;
case ODEBUG_STATE_ACTIVE:
WARN_ON(1);
default:
return false;
}
}
/*
* fixup_free is called when:
* - an active object is freed
*/
static bool 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 true;
default:
return false;
}
}
/*
* fixup_assert_init is called when:
* - an untracked/uninit-ed object is found
*/
static bool timer_fixup_assert_init(void *addr, enum debug_obj_state state)
{
struct timer_list *timer = addr;
switch (state) {
case ODEBUG_STATE_NOTAVAILABLE:
timer_setup(timer, stub_timer, 0);
return true;
default:
return false;
}
}
static struct debug_obj_descr timer_debug_descr = {
.name = "timer_list",
.debug_hint = timer_debug_hint,
.is_static_object = timer_is_static_object,
.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,
void (*func)(struct timer_list *),
unsigned int flags,
const char *name, struct lock_class_key *key);
void init_timer_on_stack_key(struct timer_list *timer,
void (*func)(struct timer_list *),
unsigned int flags,
const char *name, struct lock_class_key *key)
{
debug_object_init_on_stack(timer, &timer_debug_descr);
do_init_timer(timer, func, 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,
void (*func)(struct timer_list *),
unsigned int flags,
const char *name, struct lock_class_key *key)
{
timer->entry.pprev = NULL;
timer->function = func;
timer->flags = flags | raw_smp_processor_id();
lockdep_init_map(&timer->lockdep_map, name, key, 0);
}
/**
* init_timer_key - initialize a timer
* @timer: the timer to be initialized
* @func: timer callback function
* @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,
void (*func)(struct timer_list *), unsigned int flags,
const char *name, struct lock_class_key *key)
{
debug_init(timer);
do_init_timer(timer, func, 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 int detach_if_pending(struct timer_list *timer, struct timer_base *base,
bool clear_pending)
{
unsigned idx = timer_get_idx(timer);
if (!timer_pending(timer))
return 0;
if (hlist_is_singular_node(&timer->entry, base->vectors + idx))
__clear_bit(idx, base->pending_map);
detach_timer(timer, clear_pending);
return 1;
}
static inline struct timer_base *get_timer_cpu_base(u32 tflags, u32 cpu)
{
struct timer_base *base = per_cpu_ptr(&timer_bases[BASE_STD], cpu);
/*
* If the timer is deferrable and NO_HZ_COMMON is set then we need
* to use the deferrable base.
*/
if (IS_ENABLED(CONFIG_NO_HZ_COMMON) && (tflags & TIMER_DEFERRABLE))
base = per_cpu_ptr(&timer_bases[BASE_DEF], cpu);
return base;
}
static inline struct timer_base *get_timer_this_cpu_base(u32 tflags)
{
struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
/*
* If the timer is deferrable and NO_HZ_COMMON is set then we need
* to use the deferrable base.
*/
if (IS_ENABLED(CONFIG_NO_HZ_COMMON) && (tflags & TIMER_DEFERRABLE))
base = this_cpu_ptr(&timer_bases[BASE_DEF]);
return base;
}
static inline struct timer_base *get_timer_base(u32 tflags)
{
return get_timer_cpu_base(tflags, tflags & TIMER_CPUMASK);
}
static inline struct timer_base *
get_target_base(struct timer_base *base, unsigned tflags)
{
#if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ_COMMON)
if (static_branch_likely(&timers_migration_enabled) &&
!(tflags & TIMER_PINNED))
return get_timer_cpu_base(tflags, get_nohz_timer_target());
#endif
return get_timer_this_cpu_base(tflags);
}
static inline void forward_timer_base(struct timer_base *base)
{
#ifdef CONFIG_NO_HZ_COMMON
unsigned long jnow;
/*
* We only forward the base when we are idle or have just come out of
* idle (must_forward_clk logic), and have a delta between base clock
* and jiffies. In the common case, run_timers will take care of it.
*/
if (likely(!base->must_forward_clk))
return;
jnow = READ_ONCE(jiffies);
base->must_forward_clk = base->is_idle;
if ((long)(jnow - base->clk) < 2)
return;
/*
* If the next expiry value is > jiffies, then we fast forward to
* jiffies otherwise we forward to the next expiry value.
*/
if (time_after(base->next_expiry, jnow))
base->clk = jnow;
else
base->clk = base->next_expiry;
#endif
}
/*
* We are using hashed locking: Holding per_cpu(timer_bases[x]).lock means
* that all timers which are tied to this base are locked, and the base itself
* is locked too.
*
* So __run_timers/migrate_timers can safely modify all timers which could
* be found in the base->vectors array.
*
* When a timer is migrating then the TIMER_MIGRATING flag is set and we need
* to wait until the migration is done.
*/
static struct timer_base *lock_timer_base(struct timer_list *timer,
unsigned long *flags)
__acquires(timer->base->lock)
{
for (;;) {
struct timer_base *base;
u32 tf;
/*
* We need to use READ_ONCE() here, otherwise the compiler
* might re-read @tf between the check for TIMER_MIGRATING
* and spin_lock().
*/
tf = READ_ONCE(timer->flags);
if (!(tf & TIMER_MIGRATING)) {
base = get_timer_base(tf);
raw_spin_lock_irqsave(&base->lock, *flags);
if (timer->flags == tf)
return base;
raw_spin_unlock_irqrestore(&base->lock, *flags);
}
cpu_relax();
}
}
#define MOD_TIMER_PENDING_ONLY 0x01
#define MOD_TIMER_REDUCE 0x02
static inline int
__mod_timer(struct timer_list *timer, unsigned long expires, unsigned int options)
{
struct timer_base *base, *new_base;
unsigned int idx = UINT_MAX;
unsigned long clk = 0, flags;
int ret = 0;
BUG_ON(!timer->function);
/*
* This is a common optimization triggered by the networking code - if
* the timer is re-modified to have the same timeout or ends up in the
* same array bucket then just return:
*/
if (timer_pending(timer)) {
/*
* The downside of this optimization is that it can result in
* larger granularity than you would get from adding a new
* timer with this expiry.
*/
long diff = timer->expires - expires;
if (!diff)
return 1;
if (options & MOD_TIMER_REDUCE && diff <= 0)
return 1;
/*
* We lock timer base and calculate the bucket index right
* here. If the timer ends up in the same bucket, then we
* just update the expiry time and avoid the whole
* dequeue/enqueue dance.
*/
base = lock_timer_base(timer, &flags);
forward_timer_base(base);
if (timer_pending(timer) && (options & MOD_TIMER_REDUCE) &&
time_before_eq(timer->expires, expires)) {
ret = 1;
goto out_unlock;
}
clk = base->clk;
idx = calc_wheel_index(expires, clk);
/*
* Retrieve and compare the array index of the pending
* timer. If it matches set the expiry to the new value so a
* subsequent call will exit in the expires check above.
*/
if (idx == timer_get_idx(timer)) {
if (!(options & MOD_TIMER_REDUCE))
timer->expires = expires;
else if (time_after(timer->expires, expires))
timer->expires = expires;
ret = 1;
goto out_unlock;
}
} else {
base = lock_timer_base(timer, &flags);
forward_timer_base(base);
}
ret = detach_if_pending(timer, base, false);
if (!ret && (options & MOD_TIMER_PENDING_ONLY))
goto out_unlock;
new_base = get_target_base(base, timer->flags);
if (base != new_base) {
/*
* We are trying to schedule the timer on the new base.
* 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;
raw_spin_unlock(&base->lock);
base = new_base;
raw_spin_lock(&base->lock);
WRITE_ONCE(timer->flags,
(timer->flags & ~TIMER_BASEMASK) | base->cpu);
forward_timer_base(base);
}
}
debug_activate(timer, expires);
timer->expires = expires;
/*
* If 'idx' was calculated above and the base time did not advance
* between calculating 'idx' and possibly switching the base, only
* enqueue_timer() and trigger_dyntick_cpu() is required. Otherwise
* we need to (re)calculate the wheel index via
* internal_add_timer().
*/
if (idx != UINT_MAX && clk == base->clk) {
enqueue_timer(base, timer, idx);
trigger_dyntick_cpu(base, timer);
} else {
internal_add_timer(base, timer);
}
out_unlock:
raw_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, MOD_TIMER_PENDING_ONLY);
}
EXPORT_SYMBOL(mod_timer_pending);
/**
* 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)
{
return __mod_timer(timer, expires, 0);
}
EXPORT_SYMBOL(mod_timer);
/**
* timer_reduce - Modify a timer's timeout if it would reduce the timeout
* @timer: The timer to be modified
* @expires: New timeout in jiffies
*
* timer_reduce() is very similar to mod_timer(), except that it will only
* modify a running timer if that would reduce the expiration time (it will
* start a timer that isn't running).
*/
int timer_reduce(struct timer_list *timer, unsigned long expires)
{
return __mod_timer(timer, expires, MOD_TIMER_REDUCE);
}
EXPORT_SYMBOL(timer_reduce);
/**
* add_timer - start a timer
* @timer: the timer to be added
*
* The kernel will do a ->function(@timer) callback from the
* timer interrupt at the ->expires point in the future. The
* current time is 'jiffies'.
*
* The timer's ->expires, ->function 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 timer_base *new_base, *base;
unsigned long flags;
BUG_ON(timer_pending(timer) || !timer->function);
new_base = get_timer_cpu_base(timer->flags, cpu);
/*
* 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;
raw_spin_unlock(&base->lock);
base = new_base;
raw_spin_lock(&base->lock);
WRITE_ONCE(timer->flags,
(timer->flags & ~TIMER_BASEMASK) | cpu);
}
forward_timer_base(base);
debug_activate(timer, timer->expires);
internal_add_timer(base, timer);
raw_spin_unlock_irqrestore(&base->lock, flags);
}
EXPORT_SYMBOL_GPL(add_timer_on);
/**
* del_timer - deactivate 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 timer_base *base;
unsigned long flags;
int ret = 0;
debug_assert_init(timer);
if (timer_pending(timer)) {
base = lock_timer_base(timer, &flags);
ret = detach_if_pending(timer, base, true);
raw_spin_unlock_irqrestore(&base->lock, flags);
}
return ret;
}
EXPORT_SYMBOL(del_timer);
/**
* try_to_del_timer_sync - Try to deactivate a timer
* @timer: timer to delete
*
* 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 timer_base *base;
unsigned long flags;
int ret = -1;
debug_assert_init(timer);
base = lock_timer_base(timer, &flags);
if (base->running_timer != timer)
ret = detach_if_pending(timer, base, true);
raw_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 void call_timer_fn(struct timer_list *timer, void (*fn)(struct timer_list *))
{
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(timer);
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);
}
}
static void expire_timers(struct timer_base *base, struct hlist_head *head)
{
while (!hlist_empty(head)) {
struct timer_list *timer;
void (*fn)(struct timer_list *);
timer = hlist_entry(head->first, struct timer_list, entry);
base->running_timer = timer;
detach_timer(timer, true);
fn = timer->function;
if (timer->flags & TIMER_IRQSAFE) {
raw_spin_unlock(&base->lock);
call_timer_fn(timer, fn);
raw_spin_lock(&base->lock);
} else {
raw_spin_unlock_irq(&base->lock);
call_timer_fn(timer, fn);
raw_spin_lock_irq(&base->lock);
}
}
}
static int __collect_expired_timers(struct timer_base *base,
struct hlist_head *heads)
{
unsigned long clk = base->clk;
struct hlist_head *vec;
int i, levels = 0;
unsigned int idx;
for (i = 0; i < LVL_DEPTH; i++) {
idx = (clk & LVL_MASK) + i * LVL_SIZE;
if (__test_and_clear_bit(idx, base->pending_map)) {
vec = base->vectors + idx;
hlist_move_list(vec, heads++);
levels++;
}
/* Is it time to look at the next level? */
if (clk & LVL_CLK_MASK)
break;
/* Shift clock for the next level granularity */
clk >>= LVL_CLK_SHIFT;
}
return levels;
}
#ifdef CONFIG_NO_HZ_COMMON
/*
* Find the next pending bucket of a level. Search from level start (@offset)
* + @clk upwards and if nothing there, search from start of the level
* (@offset) up to @offset + clk.
*/
static int next_pending_bucket(struct timer_base *base, unsigned offset,
unsigned clk)
{
unsigned pos, start = offset + clk;
unsigned end = offset + LVL_SIZE;
pos = find_next_bit(base->pending_map, end, start);
if (pos < end)
return pos - start;
pos = find_next_bit(base->pending_map, start, offset);
return pos < start ? pos + LVL_SIZE - start : -1;
}
/*
* Search the first expiring timer in the various clock levels. Caller must
* hold base->lock.
*/
static unsigned long __next_timer_interrupt(struct timer_base *base)
{
unsigned long clk, next, adj;
unsigned lvl, offset = 0;
next = base->clk + NEXT_TIMER_MAX_DELTA;
clk = base->clk;
for (lvl = 0; lvl < LVL_DEPTH; lvl++, offset += LVL_SIZE) {
int pos = next_pending_bucket(base, offset, clk & LVL_MASK);
if (pos >= 0) {
unsigned long tmp = clk + (unsigned long) pos;
tmp <<= LVL_SHIFT(lvl);
if (time_before(tmp, next))
next = tmp;
}
/*
* Clock for the next level. If the current level clock lower
* bits are zero, we look at the next level as is. If not we
* need to advance it by one because that's going to be the
* next expiring bucket in that level. base->clk is the next
* expiring jiffie. So in case of:
*
* LVL5 LVL4 LVL3 LVL2 LVL1 LVL0
* 0 0 0 0 0 0
*
* we have to look at all levels @index 0. With
*
* LVL5 LVL4 LVL3 LVL2 LVL1 LVL0
* 0 0 0 0 0 2
*
* LVL0 has the next expiring bucket @index 2. The upper
* levels have the next expiring bucket @index 1.
*
* In case that the propagation wraps the next level the same
* rules apply:
*
* LVL5 LVL4 LVL3 LVL2 LVL1 LVL0
* 0 0 0 0 F 2
*
* So after looking at LVL0 we get:
*
* LVL5 LVL4 LVL3 LVL2 LVL1
* 0 0 0 1 0
*
* So no propagation from LVL1 to LVL2 because that happened
* with the add already, but then we need to propagate further
* from LVL2 to LVL3.
*
* So the simple check whether the lower bits of the current
* level are 0 or not is sufficient for all cases.
*/
adj = clk & LVL_CLK_MASK ? 1 : 0;
clk >>= LVL_CLK_SHIFT;
clk += adj;
}
return next;
}
/*
* 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 timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
u64 expires = KTIME_MAX;
unsigned long nextevt;
bool is_max_delta;
/*
* 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;
raw_spin_lock(&base->lock);
nextevt = __next_timer_interrupt(base);
is_max_delta = (nextevt == base->clk + NEXT_TIMER_MAX_DELTA);
base->next_expiry = nextevt;
/*
* We have a fresh next event. Check whether we can forward the
* base. We can only do that when @basej is past base->clk
* otherwise we might rewind base->clk.
*/
if (time_after(basej, base->clk)) {
if (time_after(nextevt, basej))
base->clk = basej;
else if (time_after(nextevt, base->clk))
base->clk = nextevt;
}
if (time_before_eq(nextevt, basej)) {
expires = basem;
base->is_idle = false;
} else {
if (!is_max_delta)
expires = basem + (u64)(nextevt - basej) * TICK_NSEC;
/*
* If we expect to sleep more than a tick, mark the base idle.
* Also the tick is stopped so any added timer must forward
* the base clk itself to keep granularity small. This idle
* logic is only maintained for the BASE_STD base, deferrable
* timers may still see large granularity skew (by design).
*/
if ((expires - basem) > TICK_NSEC) {
base->must_forward_clk = true;
base->is_idle = true;
}
}
raw_spin_unlock(&base->lock);
return cmp_next_hrtimer_event(basem, expires);
}
/**
* timer_clear_idle - Clear the idle state of the timer base
*
* Called with interrupts disabled
*/
void timer_clear_idle(void)
{
struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
/*
* We do this unlocked. The worst outcome is a remote enqueue sending
* a pointless IPI, but taking the lock would just make the window for
* sending the IPI a few instructions smaller for the cost of taking
* the lock in the exit from idle path.
*/
base->is_idle = false;
}
static int collect_expired_timers(struct timer_base *base,
struct hlist_head *heads)
{
/*
* NOHZ optimization. After a long idle sleep we need to forward the
* base to current jiffies. Avoid a loop by searching the bitfield for
* the next expiring timer.
*/
if ((long)(jiffies - base->clk) > 2) {
unsigned long next = __next_timer_interrupt(base);
/*
* If the next timer is ahead of time forward to current
* jiffies, otherwise forward to the next expiry time:
*/
if (time_after(next, jiffies)) {
/*
* The call site will increment base->clk and then
* terminate the expiry loop immediately.
*/
base->clk = jiffies;
return 0;
}
base->clk = next;
}
return __collect_expired_timers(base, heads);
}
#else
static inline int collect_expired_timers(struct timer_base *base,
struct hlist_head *heads)
{
return __collect_expired_timers(base, heads);
}
#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();
if (IS_ENABLED(CONFIG_POSIX_TIMERS))
run_posix_cpu_timers(p);
}
/**
* __run_timers - run all expired timers (if any) on this CPU.
* @base: the timer vector to be processed.
*/
static inline void __run_timers(struct timer_base *base)
{
struct hlist_head heads[LVL_DEPTH];
int levels;
if (!time_after_eq(jiffies, base->clk))
return;
raw_spin_lock_irq(&base->lock);
while (time_after_eq(jiffies, base->clk)) {
levels = collect_expired_timers(base, heads);
base->clk++;
while (levels--)
expire_timers(base, heads + levels);
}
base->running_timer = NULL;
raw_spin_unlock_irq(&base->lock);
}
/*
* This function runs timers and the timer-tq in bottom half context.
*/
static __latent_entropy void run_timer_softirq(struct softirq_action *h)
{
struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
/*
* must_forward_clk must be cleared before running timers so that any
* timer functions that call mod_timer will not try to forward the
* base. idle trcking / clock forwarding logic is only used with
* BASE_STD timers.
*
* The deferrable base does not do idle tracking at all, so we do
* not forward it. This can result in very large variations in
* granularity for deferrable timers, but they can be deferred for
* long periods due to idle.
*/
base->must_forward_clk = false;
__run_timers(base);
if (IS_ENABLED(CONFIG_NO_HZ_COMMON))
__run_timers(this_cpu_ptr(&timer_bases[BASE_DEF]));
}
/*
* Called by the local, per-CPU timer interrupt on SMP.
*/
void run_local_timers(void)
{
struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
hrtimer_run_queues();
/* Raise the softirq only if required. */
if (time_before(jiffies, base->clk)) {
if (!IS_ENABLED(CONFIG_NO_HZ_COMMON))
return;
/* CPU is awake, so check the deferrable base. */
base++;
if (time_before(jiffies, base->clk))
return;
}
raise_softirq(TIMER_SOFTIRQ);
}
/*
* Since schedule_timeout()'s timer is defined on the stack, it must store
* the target task on the stack as well.
*/
struct process_timer {
struct timer_list timer;
struct task_struct *task;
};
static void process_timeout(struct timer_list *t)
{
struct process_timer *timeout = from_timer(timeout, t, timer);
wake_up_process(timeout->task);
}
/**
* 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 unless the current task is explicitly
* woken up, (e.g. by wake_up_process())".
*
* %TASK_INTERRUPTIBLE - the routine may return early if a signal is
* delivered to the current task or the current task is explicitly woken
* up.
*
* 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.
*
* Returns 0 when the timer has expired otherwise the remaining time in
* jiffies will be returned. In all cases the return value is guaranteed
* to be non-negative.
*/
signed long __sched schedule_timeout(signed long timeout)
{
struct process_timer 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;
timer.task = current;
timer_setup_on_stack(&timer.timer, process_timeout, 0);
__mod_timer(&timer.timer, expire, 0);
schedule();
del_singleshot_timer_sync(&timer.timer);
/* Remove the timer from the object tracker */
destroy_timer_on_stack(&timer.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);
/*
* Like schedule_timeout_uninterruptible(), except this task will not contribute
* to load average.
*/
signed long __sched schedule_timeout_idle(signed long timeout)
{
__set_current_state(TASK_IDLE);
return schedule_timeout(timeout);
}
EXPORT_SYMBOL(schedule_timeout_idle);
#ifdef CONFIG_HOTPLUG_CPU
static void migrate_timer_list(struct timer_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);
detach_timer(timer, false);
timer->flags = (timer->flags & ~TIMER_BASEMASK) | cpu;
internal_add_timer(new_base, timer);
}
}
int timers_prepare_cpu(unsigned int cpu)
{
struct timer_base *base;
int b;
for (b = 0; b < NR_BASES; b++) {
base = per_cpu_ptr(&timer_bases[b], cpu);
base->clk = jiffies;
base->next_expiry = base->clk + NEXT_TIMER_MAX_DELTA;
base->is_idle = false;
base->must_forward_clk = true;
}
return 0;
}
int timers_dead_cpu(unsigned int cpu)
{
struct timer_base *old_base;
struct timer_base *new_base;
int b, i;
BUG_ON(cpu_online(cpu));
for (b = 0; b < NR_BASES; b++) {
old_base = per_cpu_ptr(&timer_bases[b], cpu);
new_base = get_cpu_ptr(&timer_bases[b]);
/*
* The caller is globally serialized and nobody else
* takes two locks at once, deadlock is not possible.
*/
raw_spin_lock_irq(&new_base->lock);
raw_spin_lock_nested(&old_base->lock, SINGLE_DEPTH_NESTING);
BUG_ON(old_base->running_timer);
for (i = 0; i < WHEEL_SIZE; i++)
migrate_timer_list(new_base, old_base->vectors + i);
raw_spin_unlock(&old_base->lock);
raw_spin_unlock_irq(&new_base->lock);
put_cpu_ptr(&timer_bases);
}
return 0;
}
#endif /* CONFIG_HOTPLUG_CPU */
static void __init init_timer_cpu(int cpu)
{
struct timer_base *base;
int i;
for (i = 0; i < NR_BASES; i++) {
base = per_cpu_ptr(&timer_bases[i], cpu);
base->cpu = cpu;
raw_spin_lock_init(&base->lock);
base->clk = 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();
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);
/**
* usleep_range - Sleep for an approximate time
* @min: Minimum time in usecs to sleep
* @max: Maximum time in usecs to sleep
*
* In non-atomic context where the exact wakeup time is flexible, use
* usleep_range() instead of udelay(). The sleep improves responsiveness
* by avoiding the CPU-hogging busy-wait of udelay(), and the range reduces
* power usage by allowing hrtimers to take advantage of an already-
* scheduled interrupt instead of scheduling a new one just for this sleep.
*/
void __sched usleep_range(unsigned long min, unsigned long max)
{
ktime_t exp = ktime_add_us(ktime_get(), min);
u64 delta = (u64)(max - min) * NSEC_PER_USEC;
for (;;) {
__set_current_state(TASK_UNINTERRUPTIBLE);
/* Do not return before the requested sleep time has elapsed */
if (!schedule_hrtimeout_range(&exp, delta, HRTIMER_MODE_ABS))
break;
}
}
EXPORT_SYMBOL(usleep_range);