diff options
Diffstat (limited to 'kernel/time/timer.c')
| -rw-r--r-- | kernel/time/timer.c | 1656 |
1 files changed, 1082 insertions, 574 deletions
diff --git a/kernel/time/timer.c b/kernel/time/timer.c index 026ac01af9da..c8f776dc6ee0 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -37,13 +37,13 @@ #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/random.h> +#include <linux/sysctl.h> #include <linux/uaccess.h> #include <asm/unistd.h> @@ -52,6 +52,7 @@ #include <asm/io.h> #include "tick-internal.h" +#include "timer_migration.h" #define CREATE_TRACE_POINTS #include <trace/events/timer.h> @@ -62,15 +63,15 @@ 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 + * LVL_SIZE buckets. Each level is driven by its own clock and therefore each * level has a different granularity. * - * The level granularity is: LVL_CLK_DIV ^ lvl + * The level granularity is: LVL_CLK_DIV ^ level * 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. + * therefore 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 @@ -157,7 +158,8 @@ EXPORT_SYMBOL(jiffies_64); /* * The time start value for each level to select the bucket at enqueue - * time. + * time. We start from the last possible delta of the previous level + * so that we can later add an extra LVL_GRAN(n) to n (see calc_index()). */ #define LVL_START(n) ((LVL_SIZE - 1) << (((n) - 1) * LVL_CLK_SHIFT)) @@ -185,15 +187,66 @@ EXPORT_SYMBOL(jiffies_64); #define WHEEL_SIZE (LVL_SIZE * LVL_DEPTH) #ifdef CONFIG_NO_HZ_COMMON -# define NR_BASES 2 -# define BASE_STD 0 -# define BASE_DEF 1 +/* + * If multiple bases need to be locked, use the base ordering for lock + * nesting, i.e. lowest number first. + */ +# define NR_BASES 3 +# define BASE_LOCAL 0 +# define BASE_GLOBAL 1 +# define BASE_DEF 2 #else # define NR_BASES 1 -# define BASE_STD 0 +# define BASE_LOCAL 0 +# define BASE_GLOBAL 0 # define BASE_DEF 0 #endif +/** + * struct timer_base - Per CPU timer base (number of base depends on config) + * @lock: Lock protecting the timer_base + * @running_timer: When expiring timers, the lock is dropped. To make + * sure not to race against deleting/modifying a + * currently running timer, the pointer is set to the + * timer, which expires at the moment. If no timer is + * running, the pointer is NULL. + * @expiry_lock: PREEMPT_RT only: Lock is taken in softirq around + * timer expiry callback execution and when trying to + * delete a running timer and it wasn't successful in + * the first glance. It prevents priority inversion + * when callback was preempted on a remote CPU and a + * caller tries to delete the running timer. It also + * prevents a life lock, when the task which tries to + * delete a timer preempted the softirq thread which + * is running the timer callback function. + * @timer_waiters: PREEMPT_RT only: Tells, if there is a waiter + * waiting for the end of the timer callback function + * execution. + * @clk: clock of the timer base; is updated before enqueue + * of a timer; during expiry, it is 1 offset ahead of + * jiffies to avoid endless requeuing to current + * jiffies + * @next_expiry: expiry value of the first timer; it is updated when + * finding the next timer and during enqueue; the + * value is not valid, when next_expiry_recalc is set + * @cpu: Number of CPU the timer base belongs to + * @next_expiry_recalc: States, whether a recalculation of next_expiry is + * required. Value is set true, when a timer was + * deleted. + * @is_idle: Is set, when timer_base is idle. It is triggered by NOHZ + * code. This state is only used in standard + * base. Deferrable timers, which are enqueued remotely + * never wake up an idle CPU. So no matter of supporting it + * for this base. + * @timers_pending: Is set, when a timer is pending in the base. It is only + * reliable when next_expiry_recalc is not set. + * @pending_map: bitmap of the timer wheel; each bit reflects a + * bucket of the wheel. When a bit is set, at least a + * single timer is enqueued in the related bucket. + * @vectors: Array of lists; Each array member reflects a bucket + * of the timer wheel. The list contains all timers + * which are enqueued into a specific bucket. + */ struct timer_base { raw_spinlock_t lock; struct timer_list *running_timer; @@ -204,8 +257,9 @@ struct timer_base { unsigned long clk; unsigned long next_expiry; unsigned int cpu; + bool next_expiry_recalc; bool is_idle; - bool must_forward_clk; + bool timers_pending; DECLARE_BITMAP(pending_map, WHEEL_SIZE); struct hlist_head vectors[WHEEL_SIZE]; } ____cacheline_aligned; @@ -221,7 +275,7 @@ 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; +static unsigned int sysctl_timer_migration = 1; DEFINE_STATIC_KEY_FALSE(timers_migration_enabled); @@ -232,7 +286,41 @@ static void timers_update_migration(void) else static_branch_disable(&timers_migration_enabled); } -#else + +#ifdef CONFIG_SYSCTL +static int timer_migration_handler(const struct ctl_table *table, int write, + void *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 const struct ctl_table timer_sysctl[] = { + { + .procname = "timer_migration", + .data = &sysctl_timer_migration, + .maxlen = sizeof(unsigned int), + .mode = 0644, + .proc_handler = timer_migration_handler, + .extra1 = SYSCTL_ZERO, + .extra2 = SYSCTL_ONE, + }, +}; + +static int __init timer_sysctl_init(void) +{ + register_sysctl("kernel", timer_sysctl); + return 0; +} +device_initcall(timer_sysctl_init); +#endif /* CONFIG_SYSCTL */ +#else /* CONFIG_SMP */ static inline void timers_update_migration(void) { } #endif /* !CONFIG_SMP */ @@ -249,19 +337,6 @@ void timers_update_nohz(void) schedule_work(&timer_update_work); } -int timer_migration_handler(struct ctl_table *table, int write, - void *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); @@ -289,7 +364,7 @@ static unsigned long round_jiffies_common(unsigned long j, int cpu, rem = j % HZ; /* - * If the target jiffie is just after a whole second (which can happen + * If the target jiffy 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. @@ -488,35 +563,48 @@ static inline void timer_set_idx(struct timer_list *timer, unsigned int idx) * Helper function to calculate the array index for a given expiry * time. */ -static inline unsigned calc_index(unsigned expires, unsigned lvl) +static inline unsigned calc_index(unsigned long expires, unsigned lvl, + unsigned long *bucket_expiry) { - expires = (expires + LVL_GRAN(lvl)) >> LVL_SHIFT(lvl); + + /* + * The timer wheel has to guarantee that a timer does not fire + * early. Early expiry can happen due to: + * - Timer is armed at the edge of a tick + * - Truncation of the expiry time in the outer wheel levels + * + * Round up with level granularity to prevent this. + */ + expires = (expires >> LVL_SHIFT(lvl)) + 1; + *bucket_expiry = expires << LVL_SHIFT(lvl); return LVL_OFFS(lvl) + (expires & LVL_MASK); } -static int calc_wheel_index(unsigned long expires, unsigned long clk) +static int calc_wheel_index(unsigned long expires, unsigned long clk, + unsigned long *bucket_expiry) { unsigned long delta = expires - clk; unsigned int idx; if (delta < LVL_START(1)) { - idx = calc_index(expires, 0); + idx = calc_index(expires, 0, bucket_expiry); } else if (delta < LVL_START(2)) { - idx = calc_index(expires, 1); + idx = calc_index(expires, 1, bucket_expiry); } else if (delta < LVL_START(3)) { - idx = calc_index(expires, 2); + idx = calc_index(expires, 2, bucket_expiry); } else if (delta < LVL_START(4)) { - idx = calc_index(expires, 3); + idx = calc_index(expires, 3, bucket_expiry); } else if (delta < LVL_START(5)) { - idx = calc_index(expires, 4); + idx = calc_index(expires, 4, bucket_expiry); } else if (delta < LVL_START(6)) { - idx = calc_index(expires, 5); + idx = calc_index(expires, 5, bucket_expiry); } else if (delta < LVL_START(7)) { - idx = calc_index(expires, 6); + idx = calc_index(expires, 6, bucket_expiry); } else if (LVL_DEPTH > 8 && delta < LVL_START(8)) { - idx = calc_index(expires, 7); + idx = calc_index(expires, 7, bucket_expiry); } else if ((long) delta < 0) { idx = clk & LVL_MASK; + *bucket_expiry = clk; } else { /* * Force expire obscene large timeouts to expire at the @@ -525,92 +613,117 @@ static int calc_wheel_index(unsigned long expires, unsigned long clk) if (delta >= WHEEL_TIMEOUT_CUTOFF) expires = clk + WHEEL_TIMEOUT_MAX; - idx = calc_index(expires, LVL_DEPTH - 1); + idx = calc_index(expires, LVL_DEPTH - 1, bucket_expiry); } 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); - - trace_timer_start(timer, timer->expires, timer->flags); -} - -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. + * Deferrable timers do not prevent the CPU from entering dynticks and + * are not taken into account on the idle/nohz_full path. An IPI when a + * new deferrable timer is enqueued will wake up the remote CPU but + * nothing will be done with the deferrable timer base. Therefore skip + * the remote IPI for deferrable timers completely. */ - if (timer->flags & TIMER_DEFERRABLE) { - if (tick_nohz_full_cpu(base->cpu)) - wake_up_nohz_cpu(base->cpu); + if (!is_timers_nohz_active() || timer->flags & TIMER_DEFERRABLE) 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: + * timer is pinned. If it is a non pinned timer, it is only queued + * on the remote CPU, when timer was running during queueing. Then + * everything is handled by remote CPU anyway. 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; + if (base->is_idle) { + WARN_ON_ONCE(!(timer->flags & TIMER_PINNED || + tick_nohz_full_cpu(base->cpu))); + wake_up_nohz_cpu(base->cpu); + } +} - /* Check whether this is the new first expiring timer: */ - if (time_after_eq(timer->expires, base->next_expiry)) - return; +/* + * Enqueue the timer into the hash bucket, mark it pending in + * the bitmap, store the index in the timer flags then wake up + * the target CPU if needed. + */ +static void enqueue_timer(struct timer_base *base, struct timer_list *timer, + unsigned int idx, unsigned long bucket_expiry) +{ + + hlist_add_head(&timer->entry, base->vectors + idx); + __set_bit(idx, base->pending_map); + timer_set_idx(timer, idx); + + trace_timer_start(timer, bucket_expiry); /* - * Set the next expiry time and kick the CPU so it can reevaluate the - * wheel: + * Check whether this is the new first expiring timer. The + * effective expiry time of the timer is required here + * (bucket_expiry) instead of timer->expires. */ - if (time_before(timer->expires, base->clk)) { + if (time_before(bucket_expiry, base->next_expiry)) { /* - * Prevent from forward_timer_base() moving the base->clk - * backward + * Set the next expiry time and kick the CPU so it + * can reevaluate the wheel: */ - base->next_expiry = base->clk; - } else { - base->next_expiry = timer->expires; + WRITE_ONCE(base->next_expiry, bucket_expiry); + base->timers_pending = true; + base->next_expiry_recalc = false; + trigger_dyntick_cpu(base, timer); } - wake_up_nohz_cpu(base->cpu); } -static void -internal_add_timer(struct timer_base *base, struct timer_list *timer) +static void internal_add_timer(struct timer_base *base, struct timer_list *timer) { - __internal_add_timer(base, timer); - trigger_dyntick_cpu(base, timer); + unsigned long bucket_expiry; + unsigned int idx; + + idx = calc_wheel_index(timer->expires, base->clk, &bucket_expiry); + enqueue_timer(base, timer, idx, bucket_expiry); } #ifdef CONFIG_DEBUG_OBJECTS_TIMERS -static struct debug_obj_descr timer_debug_descr; +static const struct debug_obj_descr timer_debug_descr; + +struct timer_hint { + void (*function)(struct timer_list *t); + long offset; +}; + +#define TIMER_HINT(fn, container, timr, hintfn) \ + { \ + .function = fn, \ + .offset = offsetof(container, hintfn) - \ + offsetof(container, timr) \ + } + +static const struct timer_hint timer_hints[] = { + TIMER_HINT(delayed_work_timer_fn, + struct delayed_work, timer, work.func), + TIMER_HINT(kthread_delayed_work_timer_fn, + struct kthread_delayed_work, timer, work.func), +}; static void *timer_debug_hint(void *addr) { - return ((struct timer_list *) addr)->function; + struct timer_list *timer = addr; + int i; + + for (i = 0; i < ARRAY_SIZE(timer_hints); i++) { + if (timer_hints[i].function == timer->function) { + void (**fn)(void) = addr + timer_hints[i].offset; + + return *fn; + } + } + + return timer->function; } static bool timer_is_static_object(void *addr) @@ -622,7 +735,7 @@ static bool timer_is_static_object(void *addr) } /* - * fixup_init is called when: + * timer_fixup_init is called when: * - an active object is initialized */ static bool timer_fixup_init(void *addr, enum debug_obj_state state) @@ -646,7 +759,7 @@ static void stub_timer(struct timer_list *unused) } /* - * fixup_activate is called when: + * timer_fixup_activate is called when: * - an active object is activated * - an unknown non-static object is activated */ @@ -661,14 +774,14 @@ static bool timer_fixup_activate(void *addr, enum debug_obj_state state) case ODEBUG_STATE_ACTIVE: WARN_ON(1); - /* fall through */ + fallthrough; default: return false; } } /* - * fixup_free is called when: + * timer_fixup_free is called when: * - an active object is freed */ static bool timer_fixup_free(void *addr, enum debug_obj_state state) @@ -686,7 +799,7 @@ static bool timer_fixup_free(void *addr, enum debug_obj_state state) } /* - * fixup_assert_init is called when: + * timer_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) @@ -702,7 +815,7 @@ static bool timer_fixup_assert_init(void *addr, enum debug_obj_state state) } } -static struct debug_obj_descr timer_debug_descr = { +static const struct debug_obj_descr timer_debug_descr = { .name = "timer_list", .debug_hint = timer_debug_hint, .is_static_object = timer_is_static_object, @@ -727,11 +840,6 @@ 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); @@ -789,6 +897,8 @@ static void do_init_timer(struct timer_list *timer, { timer->entry.pprev = NULL; timer->function = func; + if (WARN_ON_ONCE(flags & ~TIMER_INIT_FLAGS)) + flags &= TIMER_INIT_FLAGS; timer->flags = flags | raw_smp_processor_id(); lockdep_init_map(&timer->lockdep_map, name, key, 0); } @@ -802,7 +912,7 @@ static void do_init_timer(struct timer_list *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 + * init_timer_key() must be done to a timer prior to calling *any* of the * other timer functions. */ void init_timer_key(struct timer_list *timer, @@ -834,8 +944,10 @@ static int detach_if_pending(struct timer_list *timer, struct timer_base *base, if (!timer_pending(timer)) return 0; - if (hlist_is_singular_node(&timer->entry, base->vectors + idx)) + if (hlist_is_singular_node(&timer->entry, base->vectors + idx)) { __clear_bit(idx, base->pending_map); + base->next_expiry_recalc = true; + } detach_timer(timer, clear_pending); return 1; @@ -843,28 +955,30 @@ static int detach_if_pending(struct timer_list *timer, struct timer_base *base, 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); + int index = tflags & TIMER_PINNED ? BASE_LOCAL : BASE_GLOBAL; /* * 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; + index = BASE_DEF; + + return per_cpu_ptr(&timer_bases[index], cpu); } static inline struct timer_base *get_timer_this_cpu_base(u32 tflags) { - struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]); + int index = tflags & TIMER_PINNED ? BASE_LOCAL : BASE_GLOBAL; /* * 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; + index = BASE_DEF; + + return this_cpu_ptr(&timer_bases[index]); } static inline struct timer_base *get_timer_base(u32 tflags) @@ -872,49 +986,34 @@ 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) +static inline void __forward_timer_base(struct timer_base *base, + unsigned long basej) { -#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. + * 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 (likely(!base->must_forward_clk)) - return; - - jnow = READ_ONCE(jiffies); - base->must_forward_clk = base->is_idle; - if ((long)(jnow - base->clk) < 2) + if (time_before_eq(basej, base->clk)) 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; + if (time_after(base->next_expiry, basej)) { + base->clk = basej; } else { if (WARN_ON_ONCE(time_before(base->next_expiry, base->clk))) return; base->clk = base->next_expiry; } -#endif + } +static inline void forward_timer_base(struct timer_base *base) +{ + __forward_timer_base(base, READ_ONCE(jiffies)); +} /* * We are using hashed locking: Holding per_cpu(timer_bases[x]).lock means @@ -960,12 +1059,12 @@ static struct timer_base *lock_timer_base(struct timer_list *timer, static inline int __mod_timer(struct timer_list *timer, unsigned long expires, unsigned int options) { + unsigned long clk = 0, flags, bucket_expiry; struct timer_base *base, *new_base; unsigned int idx = UINT_MAX; - unsigned long clk = 0, flags; int ret = 0; - BUG_ON(!timer->function); + debug_assert_init(timer); /* * This is a common optimization triggered by the networking code - if @@ -992,6 +1091,14 @@ __mod_timer(struct timer_list *timer, unsigned long expires, unsigned int option * dequeue/enqueue dance. */ base = lock_timer_base(timer, &flags); + /* + * Has @timer been shutdown? This needs to be evaluated + * while holding base lock to prevent a race against the + * shutdown code. + */ + if (!timer->function) + goto out_unlock; + forward_timer_base(base); if (timer_pending(timer) && (options & MOD_TIMER_REDUCE) && @@ -1001,7 +1108,7 @@ __mod_timer(struct timer_list *timer, unsigned long expires, unsigned int option } clk = base->clk; - idx = calc_wheel_index(expires, clk); + idx = calc_wheel_index(expires, clk, &bucket_expiry); /* * Retrieve and compare the array index of the pending @@ -1018,6 +1125,14 @@ __mod_timer(struct timer_list *timer, unsigned long expires, unsigned int option } } else { base = lock_timer_base(timer, &flags); + /* + * Has @timer been shutdown? This needs to be evaluated + * while holding base lock to prevent a race against the + * shutdown code. + */ + if (!timer->function) + goto out_unlock; + forward_timer_base(base); } @@ -1025,13 +1140,13 @@ __mod_timer(struct timer_list *timer, unsigned long expires, unsigned int option if (!ret && (options & MOD_TIMER_PENDING_ONLY)) goto out_unlock; - new_base = get_target_base(base, timer->flags); + new_base = get_timer_this_cpu_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 + * otherwise timer_delete_sync() can't detect that the timer's * handler yet has not finished. This also guarantees that the * timer is serialized wrt itself. */ @@ -1054,16 +1169,13 @@ __mod_timer(struct timer_list *timer, unsigned long expires, unsigned int option /* * 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(). + * enqueue_timer() 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 { + if (idx != UINT_MAX && clk == base->clk) + enqueue_timer(base, timer, idx, bucket_expiry); + else internal_add_timer(base, timer); - } out_unlock: raw_spin_unlock_irqrestore(&base->lock, flags); @@ -1072,14 +1184,20 @@ out_unlock: } /** - * mod_timer_pending - modify a pending timer's timeout - * @timer: the pending timer to be modified - * @expires: new timeout in jiffies + * mod_timer_pending - Modify a pending timer's timeout + * @timer: The pending timer to be modified + * @expires: New absolute timeout in jiffies + * + * mod_timer_pending() is the same for pending timers as mod_timer(), but + * will not activate inactive timers. * - * mod_timer_pending() is the same for pending timers as mod_timer(), - * but will not re-activate and modify already deleted timers. + * If @timer->function == NULL then the start operation is silently + * discarded. * - * It is useful for unserialized use of timers. + * Return: + * * %0 - The timer was inactive and not modified or was in + * shutdown state and the operation was discarded + * * %1 - The timer was active and requeued to expire at @expires */ int mod_timer_pending(struct timer_list *timer, unsigned long expires) { @@ -1088,24 +1206,31 @@ int mod_timer_pending(struct timer_list *timer, unsigned long expires) 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 - Modify a timer's timeout + * @timer: The timer to be modified + * @expires: New absolute timeout in jiffies * * mod_timer(timer, expires) is equivalent to: * * del_timer(timer); timer->expires = expires; add_timer(timer); * + * mod_timer() is more efficient than the above open coded sequence. In + * case that the timer is inactive, the del_timer() part is a NOP. The + * timer is in any case activated with the new expiry time @expires. + * * 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.) + * If @timer->function == NULL then the start operation is silently + * discarded. In this case the return value is 0 and meaningless. + * + * Return: + * * %0 - The timer was inactive and started or was in shutdown + * state and the operation was discarded + * * %1 - The timer was active and requeued to expire at @expires or + * the timer was active and not modified because @expires did + * not change the effective expiry time */ int mod_timer(struct timer_list *timer, unsigned long expires) { @@ -1116,11 +1241,22 @@ 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 + * @expires: New absolute 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). + * modify an enqueued timer if that would reduce the expiration time. If + * @timer is not enqueued it starts the timer. + * + * If @timer->function == NULL then the start operation is silently + * discarded. + * + * Return: + * * %0 - The timer was inactive and started or was in shutdown + * state and the operation was discarded + * * %1 - The timer was active and requeued to expire at @expires or + * the timer was active and not modified because @expires + * did not change the effective expiry time such that the + * timer would expire earlier than already scheduled */ int timer_reduce(struct timer_list *timer, unsigned long expires) { @@ -1129,39 +1265,91 @@ int timer_reduce(struct timer_list *timer, unsigned long expires) EXPORT_SYMBOL(timer_reduce); /** - * add_timer - start a timer - * @timer: the timer to be added + * add_timer - Start a timer + * @timer: The timer to be started * - * The kernel will do a ->function(@timer) callback from the - * timer interrupt at the ->expires point in the future. The - * current time is 'jiffies'. + * Start @timer to expire at @timer->expires in the future. @timer->expires + * is the absolute expiry time measured in 'jiffies'. When the timer expires + * timer->function(timer) will be invoked from soft interrupt context. * - * The timer's ->expires, ->function fields must be set prior calling this - * function. + * The @timer->expires and @timer->function fields must be set prior + * to calling this function. + * + * If @timer->function == NULL then the start operation is silently + * discarded. + * + * If @timer->expires is already in the past @timer will be queued to + * expire at the next timer tick. * - * Timers with an ->expires field in the past will be executed in the next - * timer tick. + * This can only operate on an inactive timer. Attempts to invoke this on + * an active timer are rejected with a warning. */ void add_timer(struct timer_list *timer) { - BUG_ON(timer_pending(timer)); + if (WARN_ON_ONCE(timer_pending(timer))) + return; __mod_timer(timer, timer->expires, MOD_TIMER_NOTPENDING); } 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 + * add_timer_local() - Start a timer on the local CPU + * @timer: The timer to be started + * + * Same as add_timer() except that the timer flag TIMER_PINNED is set. * - * This is not very scalable on SMP. Double adds are not possible. + * See add_timer() for further details. + */ +void add_timer_local(struct timer_list *timer) +{ + if (WARN_ON_ONCE(timer_pending(timer))) + return; + timer->flags |= TIMER_PINNED; + __mod_timer(timer, timer->expires, MOD_TIMER_NOTPENDING); +} +EXPORT_SYMBOL(add_timer_local); + +/** + * add_timer_global() - Start a timer without TIMER_PINNED flag set + * @timer: The timer to be started + * + * Same as add_timer() except that the timer flag TIMER_PINNED is unset. + * + * See add_timer() for further details. + */ +void add_timer_global(struct timer_list *timer) +{ + if (WARN_ON_ONCE(timer_pending(timer))) + return; + timer->flags &= ~TIMER_PINNED; + __mod_timer(timer, timer->expires, MOD_TIMER_NOTPENDING); +} +EXPORT_SYMBOL(add_timer_global); + +/** + * add_timer_on - Start a timer on a particular CPU + * @timer: The timer to be started + * @cpu: The CPU to start it on + * + * Same as add_timer() except that it starts the timer on the given CPU and + * the TIMER_PINNED flag is set. When timer shouldn't be a pinned timer in + * the next round, add_timer_global() should be used instead as it unsets + * the TIMER_PINNED flag. + * + * See add_timer() for further details. */ 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); + debug_assert_init(timer); + + if (WARN_ON_ONCE(timer_pending(timer))) + return; + + /* Make sure timer flags have TIMER_PINNED flag set */ + timer->flags |= TIMER_PINNED; new_base = get_timer_cpu_base(timer->flags, cpu); @@ -1171,6 +1359,13 @@ void add_timer_on(struct timer_list *timer, int cpu) * wrong base locked. See lock_timer_base(). */ base = lock_timer_base(timer, &flags); + /* + * Has @timer been shutdown? This needs to be evaluated while + * holding base lock to prevent a race against the shutdown code. + */ + if (!timer->function) + goto out_unlock; + if (base != new_base) { timer->flags |= TIMER_MIGRATING; @@ -1184,22 +1379,27 @@ void add_timer_on(struct timer_list *timer, int cpu) debug_timer_activate(timer); internal_add_timer(base, timer); +out_unlock: 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.) + * __timer_delete - Internal function: Deactivate a timer + * @timer: The timer to be deactivated + * @shutdown: If true, this indicates that the timer is about to be + * shutdown permanently. + * + * If @shutdown is true then @timer->function is set to NULL under the + * timer base lock which prevents further rearming of the time. In that + * case any attempt to rearm @timer after this function returns will be + * silently ignored. + * + * Return: + * * %0 - The timer was not pending + * * %1 - The timer was pending and deactivated */ -int del_timer(struct timer_list *timer) +static int __timer_delete(struct timer_list *timer, bool shutdown) { struct timer_base *base; unsigned long flags; @@ -1207,24 +1407,90 @@ int del_timer(struct timer_list *timer) debug_assert_init(timer); - if (timer_pending(timer)) { + /* + * If @shutdown is set then the lock has to be taken whether the + * timer is pending or not to protect against a concurrent rearm + * which might hit between the lockless pending check and the lock + * acquisition. By taking the lock it is ensured that such a newly + * enqueued timer is dequeued and cannot end up with + * timer->function == NULL in the expiry code. + * + * If timer->function is currently executed, then this makes sure + * that the callback cannot requeue the timer. + */ + if (timer_pending(timer) || shutdown) { base = lock_timer_base(timer, &flags); ret = detach_if_pending(timer, base, true); + if (shutdown) + timer->function = NULL; 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 + * timer_delete - Deactivate a timer + * @timer: The timer to be deactivated + * + * The function only deactivates a pending timer, but contrary to + * timer_delete_sync() it does not take into account whether the timer's + * callback function is concurrently executed on a different CPU or not. + * It neither prevents rearming of the timer. If @timer can be rearmed + * concurrently then the return value of this function is meaningless. + * + * Return: + * * %0 - The timer was not pending + * * %1 - The timer was pending and deactivated + */ +int timer_delete(struct timer_list *timer) +{ + return __timer_delete(timer, false); +} +EXPORT_SYMBOL(timer_delete); + +/** + * timer_shutdown - Deactivate a timer and prevent rearming + * @timer: The timer to be deactivated + * + * The function does not wait for an eventually running timer callback on a + * different CPU but it prevents rearming of the timer. Any attempt to arm + * @timer after this function returns will be silently ignored. * - * 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. + * This function is useful for teardown code and should only be used when + * timer_shutdown_sync() cannot be invoked due to locking or context constraints. + * + * Return: + * * %0 - The timer was not pending + * * %1 - The timer was pending */ -int try_to_del_timer_sync(struct timer_list *timer) +int timer_shutdown(struct timer_list *timer) +{ + return __timer_delete(timer, true); +} +EXPORT_SYMBOL_GPL(timer_shutdown); + +/** + * __try_to_del_timer_sync - Internal function: Try to deactivate a timer + * @timer: Timer to deactivate + * @shutdown: If true, this indicates that the timer is about to be + * shutdown permanently. + * + * If @shutdown is true then @timer->function is set to NULL under the + * timer base lock which prevents further rearming of the timer. Any + * attempt to rearm @timer after this function returns will be silently + * ignored. + * + * This function cannot guarantee that the timer cannot be rearmed + * right after dropping the base lock if @shutdown is false. That + * needs to be prevented by the calling code if necessary. + * + * Return: + * * %0 - The timer was not pending + * * %1 - The timer was pending and deactivated + * * %-1 - The timer callback function is running on a different CPU + */ +static int __try_to_del_timer_sync(struct timer_list *timer, bool shutdown) { struct timer_base *base; unsigned long flags; @@ -1236,11 +1502,34 @@ int try_to_del_timer_sync(struct timer_list *timer) if (base->running_timer != timer) ret = detach_if_pending(timer, base, true); + if (shutdown) + timer->function = NULL; raw_spin_unlock_irqrestore(&base->lock, flags); return ret; } + +/** + * try_to_del_timer_sync - Try to deactivate a timer + * @timer: Timer to deactivate + * + * This function tries to deactivate a timer. On success the timer is not + * queued and the timer callback function is not running on any CPU. + * + * This function does not guarantee that the timer cannot be rearmed right + * after dropping the base lock. That needs to be prevented by the calling + * code if necessary. + * + * Return: + * * %0 - The timer was not pending + * * %1 - The timer was pending and deactivated + * * %-1 - The timer callback function is running on a different CPU + */ +int try_to_del_timer_sync(struct timer_list *timer) +{ + return __try_to_del_timer_sync(timer, false); +} EXPORT_SYMBOL(try_to_del_timer_sync); #ifdef CONFIG_PREEMPT_RT @@ -1263,14 +1552,18 @@ static inline void timer_base_unlock_expiry(struct timer_base *base) * The counterpart to del_timer_wait_running(). * * If there is a waiter for base->expiry_lock, then it was waiting for the - * timer callback to finish. Drop expiry_lock and reaquire it. That allows + * timer callback to finish. Drop expiry_lock and reacquire it. That allows * the waiter to acquire the lock and make progress. */ static void timer_sync_wait_running(struct timer_base *base) + __releases(&base->lock) __releases(&base->expiry_lock) + __acquires(&base->expiry_lock) __acquires(&base->lock) { if (atomic_read(&base->timer_waiters)) { + raw_spin_unlock_irq(&base->lock); spin_unlock(&base->expiry_lock); spin_lock(&base->expiry_lock); + raw_spin_lock_irq(&base->lock); } } @@ -1289,7 +1582,7 @@ static void del_timer_wait_running(struct timer_list *timer) u32 tf; tf = READ_ONCE(timer->flags); - if (!(tf & TIMER_MIGRATING)) { + if (!(tf & (TIMER_MIGRATING | TIMER_IRQSAFE))) { struct timer_base *base = get_timer_base(tf); /* @@ -1314,44 +1607,29 @@ static inline void timer_sync_wait_running(struct timer_base *base) { } static inline void del_timer_wait_running(struct timer_list *timer) { } #endif -#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT) /** - * 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. + * __timer_delete_sync - Internal function: Deactivate a timer and wait + * for the handler to finish. + * @timer: The timer to be deactivated + * @shutdown: If true, @timer->function will be set to NULL under the + * timer base lock which prevents rearming of @timer + * + * If @shutdown is not set the timer can be rearmed later. If the timer can + * be rearmed concurrently, i.e. after dropping the base lock then the + * return value is meaningless. + * + * If @shutdown is set then @timer->function is set to NULL under timer + * base lock which prevents rearming of the timer. Any attempt to rearm + * a shutdown timer is silently ignored. + * + * If the timer should be reused after shutdown it has to be initialized + * again. + * + * Return: + * * %0 - The timer was not pending + * * %1 - The timer was pending and deactivated */ -int del_timer_sync(struct timer_list *timer) +static int __timer_delete_sync(struct timer_list *timer, bool shutdown) { int ret; @@ -1371,10 +1649,17 @@ int del_timer_sync(struct timer_list *timer) * don't use it in hardirq context, because it * could lead to deadlock. */ - WARN_ON(in_irq() && !(timer->flags & TIMER_IRQSAFE)); + WARN_ON(in_hardirq() && !(timer->flags & TIMER_IRQSAFE)); + + /* + * Must be able to sleep on PREEMPT_RT because of the slowpath in + * del_timer_wait_running(). + */ + if (IS_ENABLED(CONFIG_PREEMPT_RT) && !(timer->flags & TIMER_IRQSAFE)) + lockdep_assert_preemption_enabled(); do { - ret = try_to_del_timer_sync(timer); + ret = __try_to_del_timer_sync(timer, shutdown); if (unlikely(ret < 0)) { del_timer_wait_running(timer); @@ -1384,8 +1669,96 @@ int del_timer_sync(struct timer_list *timer) return ret; } -EXPORT_SYMBOL(del_timer_sync); -#endif + +/** + * timer_delete_sync - Deactivate a timer and wait for the handler to finish. + * @timer: The timer to be deactivated + * + * 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 callback + * function. 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. + * + * For !irqsafe timers, the caller must not hold locks that are held in + * interrupt context. 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); + * timer_delete_sync(mytimer); + * while (base->running_timer == mytimer); + * + * Now timer_delete_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. + * + * This function cannot guarantee that the timer is not rearmed again by + * some concurrent or preempting code, right after it dropped the base + * lock. If there is the possibility of a concurrent rearm then the return + * value of the function is meaningless. + * + * If such a guarantee is needed, e.g. for teardown situations then use + * timer_shutdown_sync() instead. + * + * Return: + * * %0 - The timer was not pending + * * %1 - The timer was pending and deactivated + */ +int timer_delete_sync(struct timer_list *timer) +{ + return __timer_delete_sync(timer, false); +} +EXPORT_SYMBOL(timer_delete_sync); + +/** + * timer_shutdown_sync - Shutdown a timer and prevent rearming + * @timer: The timer to be shutdown + * + * When the function returns it is guaranteed that: + * - @timer is not queued + * - The callback function of @timer is not running + * - @timer cannot be enqueued again. Any attempt to rearm + * @timer is silently ignored. + * + * See timer_delete_sync() for synchronization rules. + * + * This function is useful for final teardown of an infrastructure where + * the timer is subject to a circular dependency problem. + * + * A common pattern for this is a timer and a workqueue where the timer can + * schedule work and work can arm the timer. On shutdown the workqueue must + * be destroyed and the timer must be prevented from rearming. Unless the + * code has conditionals like 'if (mything->in_shutdown)' to prevent that + * there is no way to get this correct with timer_delete_sync(). + * + * timer_shutdown_sync() is solving the problem. The correct ordering of + * calls in this case is: + * + * timer_shutdown_sync(&mything->timer); + * workqueue_destroy(&mything->workqueue); + * + * After this 'mything' can be safely freed. + * + * This obviously implies that the timer is not required to be functional + * for the rest of the shutdown operation. + * + * Return: + * * %0 - The timer was not pending + * * %1 - The timer was pending + */ +int timer_shutdown_sync(struct timer_list *timer) +{ + return __timer_delete_sync(timer, true); +} +EXPORT_SYMBOL_GPL(timer_shutdown_sync); static void call_timer_fn(struct timer_list *timer, void (*fn)(struct timer_list *), @@ -1407,8 +1780,8 @@ static void call_timer_fn(struct timer_list *timer, #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(). + * timer_delete_sync() by acquiring the lock_map around the fn() + * call here and in timer_delete_sync(). */ lock_map_acquire(&lockdep_map); @@ -1451,25 +1824,31 @@ static void expire_timers(struct timer_base *base, struct hlist_head *head) fn = timer->function; + if (WARN_ON_ONCE(!fn)) { + /* Should never happen. Emphasis on should! */ + base->running_timer = NULL; + continue; + } + if (timer->flags & TIMER_IRQSAFE) { raw_spin_unlock(&base->lock); call_timer_fn(timer, fn, baseclk); - base->running_timer = NULL; raw_spin_lock(&base->lock); + base->running_timer = NULL; } else { raw_spin_unlock_irq(&base->lock); call_timer_fn(timer, fn, baseclk); + raw_spin_lock_irq(&base->lock); base->running_timer = NULL; timer_sync_wait_running(base); - raw_spin_lock_irq(&base->lock); } } } -static int __collect_expired_timers(struct timer_base *base, - struct hlist_head *heads) +static int collect_expired_timers(struct timer_base *base, + struct hlist_head *heads) { - unsigned long clk = base->clk; + unsigned long clk = base->clk = base->next_expiry; struct hlist_head *vec; int i, levels = 0; unsigned int idx; @@ -1491,7 +1870,6 @@ static int __collect_expired_timers(struct timer_base *base, 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 @@ -1514,8 +1892,10 @@ static int next_pending_bucket(struct timer_base *base, unsigned offset, /* * Search the first expiring timer in the various clock levels. Caller must * hold base->lock. + * + * Store next expiry time in base->next_expiry. */ -static unsigned long __next_timer_interrupt(struct timer_base *base) +static void timer_recalc_next_expiry(struct timer_base *base) { unsigned long clk, next, adj; unsigned lvl, offset = 0; @@ -1524,6 +1904,7 @@ static unsigned long __next_timer_interrupt(struct timer_base *base) clk = base->clk; for (lvl = 0; lvl < LVL_DEPTH; lvl++, offset += LVL_SIZE) { int pos = next_pending_bucket(base, offset, clk & LVL_MASK); + unsigned long lvl_clk = clk & LVL_CLK_MASK; if (pos >= 0) { unsigned long tmp = clk + (unsigned long) pos; @@ -1531,13 +1912,20 @@ static unsigned long __next_timer_interrupt(struct timer_base *base) tmp <<= LVL_SHIFT(lvl); if (time_before(tmp, next)) next = tmp; + + /* + * If the next expiration happens before we reach + * the next level, no need to check further. + */ + if (pos <= ((LVL_CLK_DIV - lvl_clk) & LVL_CLK_MASK)) + break; } /* * 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: + * expiring jiffy. So in case of: * * LVL5 LVL4 LVL3 LVL2 LVL1 LVL0 * 0 0 0 0 0 0 @@ -1568,13 +1956,17 @@ static unsigned long __next_timer_interrupt(struct timer_base *base) * 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; + adj = lvl_clk ? 1 : 0; clk >>= LVL_CLK_SHIFT; clk += adj; } - return next; + + WRITE_ONCE(base->next_expiry, next); + base->next_expiry_recalc = false; + base->timers_pending = !(next == base->clk + NEXT_TIMER_MAX_DELTA); } +#ifdef CONFIG_NO_HZ_COMMON /* * Check, if the next hrtimer event is before the next timer wheel * event: @@ -1598,7 +1990,7 @@ static u64 cmp_next_hrtimer_event(u64 basem, u64 expires) return basem; /* - * Round up to the next jiffie. High resolution timers are + * Round up to the next jiffy. 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. @@ -1608,149 +2000,382 @@ static u64 cmp_next_hrtimer_event(u64 basem, u64 expires) 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) +static unsigned long next_timer_interrupt(struct timer_base *base, + unsigned long basej) { - struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]); - u64 expires = KTIME_MAX; - unsigned long nextevt; - bool is_max_delta; + if (base->next_expiry_recalc) + timer_recalc_next_expiry(base); /* - * Pretend that there is no timer pending if the cpu is offline. - * Possible pending timers will be migrated later to an active cpu. + * Move next_expiry for the empty base into the future to prevent an + * unnecessary raise of the timer softirq when the next_expiry value + * will be reached even if there is no timer pending. + * + * This update is also required to make timer_base::next_expiry values + * easy comparable to find out which base holds the first pending timer. */ - if (cpu_is_offline(smp_processor_id())) - return expires; + if (!base->timers_pending) + WRITE_ONCE(base->next_expiry, basej + NEXT_TIMER_MAX_DELTA); + + return base->next_expiry; +} + +static unsigned long fetch_next_timer_interrupt(unsigned long basej, u64 basem, + struct timer_base *base_local, + struct timer_base *base_global, + struct timer_events *tevt) +{ + unsigned long nextevt, nextevt_local, nextevt_global; + bool local_first; + + nextevt_local = next_timer_interrupt(base_local, basej); + nextevt_global = next_timer_interrupt(base_global, basej); + + local_first = time_before_eq(nextevt_local, nextevt_global); + + nextevt = local_first ? nextevt_local : nextevt_global; - 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 the @nextevt is at max. one tick away, use @nextevt and store + * it in the local expiry value. The next global event is irrelevant in + * this case and can be left as KTIME_MAX. */ - 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 + 1)) { + /* If we missed a tick already, force 0 delta */ + if (time_before(nextevt, basej)) + nextevt = basej; + tevt->local = basem + (u64)(nextevt - basej) * TICK_NSEC; - 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). + * This is required for the remote check only but it doesn't + * hurt, when it is done for both call sites: + * + * * The remote callers will only take care of the global timers + * as local timers will be handled by CPU itself. When not + * updating tevt->global with the already missed first global + * timer, it is possible that it will be missed completely. + * + * * The local callers will ignore the tevt->global anyway, when + * nextevt is max. one tick away. */ - if ((expires - basem) > TICK_NSEC) { - base->must_forward_clk = true; - base->is_idle = true; - } + if (!local_first) + tevt->global = tevt->local; + return nextevt; } - raw_spin_unlock(&base->lock); - return cmp_next_hrtimer_event(basem, expires); + /* + * Update tevt.* values: + * + * If the local queue expires first, then the global event can be + * ignored. If the global queue is empty, nothing to do either. + */ + if (!local_first && base_global->timers_pending) + tevt->global = basem + (u64)(nextevt_global - basej) * TICK_NSEC; + + if (base_local->timers_pending) + tevt->local = basem + (u64)(nextevt_local - basej) * TICK_NSEC; + + return nextevt; } +# ifdef CONFIG_SMP /** - * timer_clear_idle - Clear the idle state of the timer base + * fetch_next_timer_interrupt_remote() - Store next timers into @tevt + * @basej: base time jiffies + * @basem: base time clock monotonic + * @tevt: Pointer to the storage for the expiry values + * @cpu: Remote CPU * - * Called with interrupts disabled + * Stores the next pending local and global timer expiry values in the + * struct pointed to by @tevt. If a queue is empty the corresponding + * field is set to KTIME_MAX. If local event expires before global + * event, global event is set to KTIME_MAX as well. + * + * Caller needs to make sure timer base locks are held (use + * timer_lock_remote_bases() for this purpose). */ -void timer_clear_idle(void) +void fetch_next_timer_interrupt_remote(unsigned long basej, u64 basem, + struct timer_events *tevt, + unsigned int cpu) +{ + struct timer_base *base_local, *base_global; + + /* Preset local / global events */ + tevt->local = tevt->global = KTIME_MAX; + + base_local = per_cpu_ptr(&timer_bases[BASE_LOCAL], cpu); + base_global = per_cpu_ptr(&timer_bases[BASE_GLOBAL], cpu); + + lockdep_assert_held(&base_local->lock); + lockdep_assert_held(&base_global->lock); + + fetch_next_timer_interrupt(basej, basem, base_local, base_global, tevt); +} + +/** + * timer_unlock_remote_bases - unlock timer bases of cpu + * @cpu: Remote CPU + * + * Unlocks the remote timer bases. + */ +void timer_unlock_remote_bases(unsigned int cpu) + __releases(timer_bases[BASE_LOCAL]->lock) + __releases(timer_bases[BASE_GLOBAL]->lock) +{ + struct timer_base *base_local, *base_global; + + base_local = per_cpu_ptr(&timer_bases[BASE_LOCAL], cpu); + base_global = per_cpu_ptr(&timer_bases[BASE_GLOBAL], cpu); + + raw_spin_unlock(&base_global->lock); + raw_spin_unlock(&base_local->lock); +} + +/** + * timer_lock_remote_bases - lock timer bases of cpu + * @cpu: Remote CPU + * + * Locks the remote timer bases. + */ +void timer_lock_remote_bases(unsigned int cpu) + __acquires(timer_bases[BASE_LOCAL]->lock) + __acquires(timer_bases[BASE_GLOBAL]->lock) +{ + struct timer_base *base_local, *base_global; + + base_local = per_cpu_ptr(&timer_bases[BASE_LOCAL], cpu); + base_global = per_cpu_ptr(&timer_bases[BASE_GLOBAL], cpu); + + lockdep_assert_irqs_disabled(); + + raw_spin_lock(&base_local->lock); + raw_spin_lock_nested(&base_global->lock, SINGLE_DEPTH_NESTING); +} + +/** + * timer_base_is_idle() - Return whether timer base is set idle + * + * Returns value of local timer base is_idle value. + */ +bool timer_base_is_idle(void) { - struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]); + return __this_cpu_read(timer_bases[BASE_LOCAL].is_idle); +} + +static void __run_timer_base(struct timer_base *base); + +/** + * timer_expire_remote() - expire global timers of cpu + * @cpu: Remote CPU + * + * Expire timers of global base of remote CPU. + */ +void timer_expire_remote(unsigned int cpu) +{ + struct timer_base *base = per_cpu_ptr(&timer_bases[BASE_GLOBAL], cpu); + + __run_timer_base(base); +} + +static void timer_use_tmigr(unsigned long basej, u64 basem, + unsigned long *nextevt, bool *tick_stop_path, + bool timer_base_idle, struct timer_events *tevt) +{ + u64 next_tmigr; + + if (timer_base_idle) + next_tmigr = tmigr_cpu_new_timer(tevt->global); + else if (tick_stop_path) + next_tmigr = tmigr_cpu_deactivate(tevt->global); + else + next_tmigr = tmigr_quick_check(tevt->global); /* - * 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. + * If the CPU is the last going idle in timer migration hierarchy, make + * sure the CPU will wake up in time to handle remote timers. + * next_tmigr == KTIME_MAX if other CPUs are still active. */ - base->is_idle = false; + if (next_tmigr < tevt->local) { + u64 tmp; + + /* If we missed a tick already, force 0 delta */ + if (next_tmigr < basem) + next_tmigr = basem; + + tmp = div_u64(next_tmigr - basem, TICK_NSEC); + + *nextevt = basej + (unsigned long)tmp; + tevt->local = next_tmigr; + } } +# else +static void timer_use_tmigr(unsigned long basej, u64 basem, + unsigned long *nextevt, bool *tick_stop_path, + bool timer_base_idle, struct timer_events *tevt) +{ + /* + * Make sure first event is written into tevt->local to not miss a + * timer on !SMP systems. + */ + tevt->local = min_t(u64, tevt->local, tevt->global); +} +# endif /* CONFIG_SMP */ -static int collect_expired_timers(struct timer_base *base, - struct hlist_head *heads) +static inline u64 __get_next_timer_interrupt(unsigned long basej, u64 basem, + bool *idle) { - unsigned long now = READ_ONCE(jiffies); + struct timer_events tevt = { .local = KTIME_MAX, .global = KTIME_MAX }; + struct timer_base *base_local, *base_global; + unsigned long nextevt; + bool idle_is_possible; + + /* + * When the CPU is offline, the tick is cancelled and nothing is supposed + * to try to stop it. + */ + if (WARN_ON_ONCE(cpu_is_offline(smp_processor_id()))) { + if (idle) + *idle = true; + return tevt.local; + } + + base_local = this_cpu_ptr(&timer_bases[BASE_LOCAL]); + base_global = this_cpu_ptr(&timer_bases[BASE_GLOBAL]); + + raw_spin_lock(&base_local->lock); + raw_spin_lock_nested(&base_global->lock, SINGLE_DEPTH_NESTING); + + nextevt = fetch_next_timer_interrupt(basej, basem, base_local, + base_global, &tevt); + + /* + * If the next event is only one jiffy ahead there is no need to call + * timer migration hierarchy related functions. The value for the next + * global timer in @tevt struct equals then KTIME_MAX. This is also + * true, when the timer base is idle. + * + * The proper timer migration hierarchy function depends on the callsite + * and whether timer base is idle or not. @nextevt will be updated when + * this CPU needs to handle the first timer migration hierarchy + * event. See timer_use_tmigr() for detailed information. + */ + idle_is_possible = time_after(nextevt, basej + 1); + if (idle_is_possible) + timer_use_tmigr(basej, basem, &nextevt, idle, + base_local->is_idle, &tevt); /* - * 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. + * We have a fresh next event. Check whether we can forward the + * base. */ - if ((long)(now - base->clk) > 2) { - unsigned long next = __next_timer_interrupt(base); + __forward_timer_base(base_local, basej); + __forward_timer_base(base_global, basej); + /* + * Set base->is_idle only when caller is timer_base_try_to_set_idle() + */ + if (idle) { /* - * If the next timer is ahead of time forward to current - * jiffies, otherwise forward to the next expiry time: + * Bases are idle if the next event is more than a tick + * away. Caution: @nextevt could have changed by enqueueing a + * global timer into timer migration hierarchy. Therefore a new + * check is required here. + * + * If the base is marked idle then any timer add operation must + * forward the base clk itself to keep granularity small. This + * idle logic is only maintained for the BASE_LOCAL and + * BASE_GLOBAL base, deferrable timers may still see large + * granularity skew (by design). */ - if (time_after(next, now)) { + if (!base_local->is_idle && time_after(nextevt, basej + 1)) { + base_local->is_idle = true; /* - * The call site will increment base->clk and then - * terminate the expiry loop immediately. + * Global timers queued locally while running in a task + * in nohz_full mode need a self-IPI to kick reprogramming + * in IRQ tail. */ - base->clk = now; - return 0; + if (tick_nohz_full_cpu(base_local->cpu)) + base_global->is_idle = true; + trace_timer_base_idle(true, base_local->cpu); } - base->clk = next; + *idle = base_local->is_idle; + + /* + * When timer base is not set idle, undo the effect of + * tmigr_cpu_deactivate() to prevent inconsistent states - active + * timer base but inactive timer migration hierarchy. + * + * When timer base was already marked idle, nothing will be + * changed here. + */ + if (!base_local->is_idle && idle_is_possible) + tmigr_cpu_activate(); } - return __collect_expired_timers(base, heads); + + raw_spin_unlock(&base_global->lock); + raw_spin_unlock(&base_local->lock); + + return cmp_next_hrtimer_event(basem, tevt.local); } -#else -static inline int collect_expired_timers(struct timer_base *base, - struct hlist_head *heads) + +/** + * 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. If timer of global base was queued into + * timer migration hierarchy, first global timer is not taken into account. If + * it was the last CPU of timer migration hierarchy going idle, first global + * event is taken into account. + */ +u64 get_next_timer_interrupt(unsigned long basej, u64 basem) { - return __collect_expired_timers(base, heads); + return __get_next_timer_interrupt(basej, basem, NULL); } -#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. +/** + * timer_base_try_to_set_idle() - Try to set the idle state of the timer bases + * @basej: base time jiffies + * @basem: base time clock monotonic + * @idle: pointer to store the value of timer_base->is_idle on return; + * *idle contains the information whether tick was already stopped + * + * Returns the tick aligned clock monotonic time of the next pending timer or + * KTIME_MAX if no timer is pending. When tick was already stopped KTIME_MAX is + * returned as well. */ -void update_process_times(int user_tick) +u64 timer_base_try_to_set_idle(unsigned long basej, u64 basem, bool *idle) { - struct task_struct *p = current; + if (*idle) + return KTIME_MAX; - /* Note: this timer irq context must be accounted for as well. */ - account_process_tick(p, user_tick); - run_local_timers(); - rcu_sched_clock_irq(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(); + return __get_next_timer_interrupt(basej, basem, idle); +} - /* The current CPU might make use of net randoms without receiving IRQs - * to renew them often enough. Let's update the net_rand_state from a - * non-constant value that's not affine to the number of calls to make - * sure it's updated when there's some activity (we don't care in idle). +/** + * timer_clear_idle - Clear the idle state of the timer base + * + * Called with interrupts disabled + */ +void timer_clear_idle(void) +{ + /* + * We do this unlocked. The worst outcome is a remote pinned timer + * 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. Required for BASE_LOCAL only. */ - this_cpu_add(net_rand_state.s1, rol32(jiffies, 24) + user_tick); + __this_cpu_write(timer_bases[BASE_LOCAL].is_idle, false); + if (tick_nohz_full_cpu(smp_processor_id())) + __this_cpu_write(timer_bases[BASE_GLOBAL].is_idle, false); + trace_timer_base_idle(false, smp_processor_id()); + + /* Activate without holding the timer_base->lock */ + tmigr_cpu_activate(); } +#endif /** * __run_timers - run all expired timers (if any) on this CPU. @@ -1761,206 +2386,141 @@ 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; - - timer_base_lock_expiry(base); - raw_spin_lock_irq(&base->lock); - - /* - * timer_base::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 tracking / clock forwarding - * logic is only used with BASE_STD timers. - * - * The must_forward_clk flag is cleared unconditionally also for - * the deferrable base. The deferrable base is not affected by idle - * tracking and never forwarded, so clearing the flag is a NOOP. - * - * The fact that the deferrable base is never forwarded can cause - * large variations in granularity for deferrable timers, but they - * can be deferred for long periods due to idle anyway. - */ - base->must_forward_clk = false; + lockdep_assert_held(&base->lock); - while (time_after_eq(jiffies, base->clk)) { + if (base->running_timer) + return; + while (time_after_eq(jiffies, base->clk) && + time_after_eq(jiffies, base->next_expiry)) { levels = collect_expired_timers(base, heads); + /* + * The two possible reasons for not finding any expired + * timer at this clk are that all matching timers have been + * dequeued or no timer has been queued since + * base::next_expiry was set to base::clk + + * NEXT_TIMER_MAX_DELTA. + */ + WARN_ON_ONCE(!levels && !base->next_expiry_recalc + && base->timers_pending); + /* + * While executing timers, base->clk is set 1 offset ahead of + * jiffies to avoid endless requeuing to current jiffies. + */ base->clk++; + timer_recalc_next_expiry(base); while (levels--) expire_timers(base, heads + levels); } - raw_spin_unlock_irq(&base->lock); - timer_base_unlock_expiry(base); } -/* - * This function runs timers and the timer-tq in bottom half context. - */ -static __latent_entropy void run_timer_softirq(struct softirq_action *h) +static void __run_timer_base(struct timer_base *base) { - struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]); + /* Can race against a remote CPU updating next_expiry under the lock */ + if (time_before(jiffies, READ_ONCE(base->next_expiry))) + return; + timer_base_lock_expiry(base); + raw_spin_lock_irq(&base->lock); __run_timers(base); - if (IS_ENABLED(CONFIG_NO_HZ_COMMON)) - __run_timers(this_cpu_ptr(&timer_bases[BASE_DEF])); + raw_spin_unlock_irq(&base->lock); + timer_base_unlock_expiry(base); } -/* - * Called by the local, per-CPU timer interrupt on SMP. - */ -void run_local_timers(void) +static void run_timer_base(int index) { - struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]); + struct timer_base *base = this_cpu_ptr(&timer_bases[index]); - 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); + __run_timer_base(base); } /* - * Since schedule_timeout()'s timer is defined on the stack, it must store - * the target task on the stack as well. + * This function runs timers and the timer-tq in bottom half context. */ -struct process_timer { - struct timer_list timer; - struct task_struct *task; -}; - -static void process_timeout(struct timer_list *t) +static __latent_entropy void run_timer_softirq(void) { - struct process_timer *timeout = from_timer(timeout, t, timer); + run_timer_base(BASE_LOCAL); + if (IS_ENABLED(CONFIG_NO_HZ_COMMON)) { + run_timer_base(BASE_GLOBAL); + run_timer_base(BASE_DEF); - wake_up_process(timeout->task); + if (is_timers_nohz_active()) + tmigr_handle_remote(); + } } -/** - * schedule_timeout - sleep until timeout - * @timeout: timeout value in jiffies - * - * Make the current task sleep until @timeout jiffies have elapsed. - * The function behavior depends on the current task state - * (see also set_current_state() description): - * - * %TASK_RUNNING - the scheduler is called, but the task does not sleep - * at all. That happens because sched_submit_work() does nothing for - * tasks in %TASK_RUNNING state. - * - * %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. +/* + * Called by the local, per-CPU timer interrupt on SMP. */ -signed long __sched schedule_timeout(signed long timeout) +static void run_local_timers(void) { - struct process_timer timer; - unsigned long expire; + struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_LOCAL]); - 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: + hrtimer_run_queues(); + + for (int i = 0; i < NR_BASES; i++, base++) { /* - * 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. + * Raise the softirq only if required. + * + * timer_base::next_expiry can be written by a remote CPU while + * holding the lock. If this write happens at the same time than + * the lockless local read, sanity checker could complain about + * data corruption. + * + * There are two possible situations where + * timer_base::next_expiry is written by a remote CPU: + * + * 1. Remote CPU expires global timers of this CPU and updates + * timer_base::next_expiry of BASE_GLOBAL afterwards in + * next_timer_interrupt() or timer_recalc_next_expiry(). The + * worst outcome is a superfluous raise of the timer softirq + * when the not yet updated value is read. + * + * 2. A new first pinned timer is enqueued by a remote CPU + * and therefore timer_base::next_expiry of BASE_LOCAL is + * updated. When this update is missed, this isn't a + * problem, as an IPI is executed nevertheless when the CPU + * was idle before. When the CPU wasn't idle but the update + * is missed, then the timer would expire one jiffy late - + * bad luck. + * + * Those unlikely corner cases where the worst outcome is only a + * one jiffy delay or a superfluous raise of the softirq are + * not that expensive as doing the check always while holding + * the lock. + * + * Possible remote writers are using WRITE_ONCE(). Local reader + * uses therefore READ_ONCE(). */ - if (timeout < 0) { - printk(KERN_ERR "schedule_timeout: wrong timeout " - "value %lx\n", timeout); - dump_stack(); - current->state = TASK_RUNNING; - goto out; + if (time_after_eq(jiffies, READ_ONCE(base->next_expiry)) || + (i == BASE_DEF && tmigr_requires_handle_remote())) { + raise_timer_softirq(TIMER_SOFTIRQ); + return; } } - - expire = timeout + jiffies; - - timer.task = current; - timer_setup_on_stack(&timer.timer, process_timeout, 0); - __mod_timer(&timer.timer, expire, MOD_TIMER_NOTPENDING); - 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. + * 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. */ -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) +void update_process_times(int user_tick) { - __set_current_state(TASK_UNINTERRUPTIBLE); - return schedule_timeout(timeout); -} -EXPORT_SYMBOL(schedule_timeout_uninterruptible); + struct task_struct *p = current; -/* - * 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); + /* Note: this timer irq context must be accounted for as well. */ + account_process_tick(p, user_tick); + run_local_timers(); + rcu_sched_clock_irq(user_tick); +#ifdef CONFIG_IRQ_WORK + if (in_irq()) + irq_work_tick(); +#endif + sched_tick(); + if (IS_ENABLED(CONFIG_POSIX_TIMERS)) + run_posix_cpu_timers(); } -EXPORT_SYMBOL(schedule_timeout_idle); #ifdef CONFIG_HOTPLUG_CPU static void migrate_timer_list(struct timer_base *new_base, struct hlist_head *head) @@ -1985,8 +2545,9 @@ int timers_prepare_cpu(unsigned int cpu) base = per_cpu_ptr(&timer_bases[b], cpu); base->clk = jiffies; base->next_expiry = base->clk + NEXT_TIMER_MAX_DELTA; + base->next_expiry_recalc = false; + base->timers_pending = false; base->is_idle = false; - base->must_forward_clk = true; } return 0; } @@ -1997,8 +2558,6 @@ int timers_dead_cpu(unsigned int cpu) 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]); @@ -2015,7 +2574,8 @@ int timers_dead_cpu(unsigned int cpu) */ forward_timer_base(new_base); - BUG_ON(old_base->running_timer); + WARN_ON_ONCE(old_base->running_timer); + old_base->running_timer = NULL; for (i = 0; i < WHEEL_SIZE; i++) migrate_timer_list(new_base, old_base->vectors + i); @@ -2039,6 +2599,7 @@ static void __init init_timer_cpu(int cpu) base->cpu = cpu; raw_spin_lock_init(&base->lock); base->clk = jiffies; + base->next_expiry = base->clk + NEXT_TIMER_MAX_DELTA; timer_base_init_expiry_lock(base); } } @@ -2054,59 +2615,6 @@ static void __init init_timer_cpus(void) void __init init_timers(void) { init_timer_cpus(); + posix_cputimers_init_work(); 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); |