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-rw-r--r--kernel/time/tick-sched.c320
1 files changed, 132 insertions, 188 deletions
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 914259128145..c792429e98c6 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -399,7 +399,7 @@ void __init tick_nohz_init(void)
* NO HZ enabled ?
*/
static int tick_nohz_enabled __read_mostly = 1;
-int tick_nohz_active __read_mostly;
+unsigned long tick_nohz_active __read_mostly;
/*
* Enable / Disable tickless mode
*/
@@ -565,156 +565,144 @@ u64 get_cpu_iowait_time_us(int cpu, u64 *last_update_time)
}
EXPORT_SYMBOL_GPL(get_cpu_iowait_time_us);
+static void tick_nohz_restart(struct tick_sched *ts, ktime_t now)
+{
+ hrtimer_cancel(&ts->sched_timer);
+ hrtimer_set_expires(&ts->sched_timer, ts->last_tick);
+
+ /* Forward the time to expire in the future */
+ hrtimer_forward(&ts->sched_timer, now, tick_period);
+
+ if (ts->nohz_mode == NOHZ_MODE_HIGHRES)
+ hrtimer_start_expires(&ts->sched_timer, HRTIMER_MODE_ABS_PINNED);
+ else
+ tick_program_event(hrtimer_get_expires(&ts->sched_timer), 1);
+}
+
static ktime_t tick_nohz_stop_sched_tick(struct tick_sched *ts,
ktime_t now, int cpu)
{
- unsigned long seq, last_jiffies, next_jiffies, delta_jiffies;
- ktime_t last_update, expires, ret = { .tv64 = 0 };
- unsigned long rcu_delta_jiffies;
struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
- u64 time_delta;
-
- time_delta = timekeeping_max_deferment();
+ u64 basemono, next_tick, next_tmr, next_rcu, delta, expires;
+ unsigned long seq, basejiff;
+ ktime_t tick;
/* Read jiffies and the time when jiffies were updated last */
do {
seq = read_seqbegin(&jiffies_lock);
- last_update = last_jiffies_update;
- last_jiffies = jiffies;
+ basemono = last_jiffies_update.tv64;
+ basejiff = jiffies;
} while (read_seqretry(&jiffies_lock, seq));
+ ts->last_jiffies = basejiff;
- if (rcu_needs_cpu(&rcu_delta_jiffies) ||
+ if (rcu_needs_cpu(basemono, &next_rcu) ||
arch_needs_cpu() || irq_work_needs_cpu()) {
- next_jiffies = last_jiffies + 1;
- delta_jiffies = 1;
+ next_tick = basemono + TICK_NSEC;
} else {
- /* Get the next timer wheel timer */
- next_jiffies = get_next_timer_interrupt(last_jiffies);
- delta_jiffies = next_jiffies - last_jiffies;
- if (rcu_delta_jiffies < delta_jiffies) {
- next_jiffies = last_jiffies + rcu_delta_jiffies;
- delta_jiffies = rcu_delta_jiffies;
- }
+ /*
+ * Get the next pending timer. If high resolution
+ * timers are enabled this only takes the timer wheel
+ * timers into account. If high resolution timers are
+ * disabled this also looks at the next expiring
+ * hrtimer.
+ */
+ next_tmr = get_next_timer_interrupt(basejiff, basemono);
+ ts->next_timer = next_tmr;
+ /* Take the next rcu event into account */
+ next_tick = next_rcu < next_tmr ? next_rcu : next_tmr;
}
/*
- * Do not stop the tick, if we are only one off (or less)
- * or if the cpu is required for RCU:
+ * If the tick is due in the next period, keep it ticking or
+ * restart it proper.
*/
- if (!ts->tick_stopped && delta_jiffies <= 1)
- goto out;
-
- /* Schedule the tick, if we are at least one jiffie off */
- if ((long)delta_jiffies >= 1) {
-
- /*
- * If this cpu is the one which updates jiffies, then
- * give up the assignment and let it be taken by the
- * cpu which runs the tick timer next, which might be
- * this cpu as well. If we don't drop this here the
- * jiffies might be stale and do_timer() never
- * invoked. Keep track of the fact that it was the one
- * which had the do_timer() duty last. If this cpu is
- * the one which had the do_timer() duty last, we
- * limit the sleep time to the timekeeping
- * max_deferement value which we retrieved
- * above. Otherwise we can sleep as long as we want.
- */
- if (cpu == tick_do_timer_cpu) {
- tick_do_timer_cpu = TICK_DO_TIMER_NONE;
- ts->do_timer_last = 1;
- } else if (tick_do_timer_cpu != TICK_DO_TIMER_NONE) {
- time_delta = KTIME_MAX;
- ts->do_timer_last = 0;
- } else if (!ts->do_timer_last) {
- time_delta = KTIME_MAX;
+ delta = next_tick - basemono;
+ if (delta <= (u64)TICK_NSEC) {
+ tick.tv64 = 0;
+ if (!ts->tick_stopped)
+ goto out;
+ if (delta == 0) {
+ /* Tick is stopped, but required now. Enforce it */
+ tick_nohz_restart(ts, now);
+ goto out;
}
+ }
+
+ /*
+ * If this cpu is the one which updates jiffies, then give up
+ * the assignment and let it be taken by the cpu which runs
+ * the tick timer next, which might be this cpu as well. If we
+ * don't drop this here the jiffies might be stale and
+ * do_timer() never invoked. Keep track of the fact that it
+ * was the one which had the do_timer() duty last. If this cpu
+ * is the one which had the do_timer() duty last, we limit the
+ * sleep time to the timekeeping max_deferement value.
+ * Otherwise we can sleep as long as we want.
+ */
+ delta = timekeeping_max_deferment();
+ if (cpu == tick_do_timer_cpu) {
+ tick_do_timer_cpu = TICK_DO_TIMER_NONE;
+ ts->do_timer_last = 1;
+ } else if (tick_do_timer_cpu != TICK_DO_TIMER_NONE) {
+ delta = KTIME_MAX;
+ ts->do_timer_last = 0;
+ } else if (!ts->do_timer_last) {
+ delta = KTIME_MAX;
+ }
#ifdef CONFIG_NO_HZ_FULL
- if (!ts->inidle) {
- time_delta = min(time_delta,
- scheduler_tick_max_deferment());
- }
+ /* Limit the tick delta to the maximum scheduler deferment */
+ if (!ts->inidle)
+ delta = min(delta, scheduler_tick_max_deferment());
#endif
- /*
- * calculate the expiry time for the next timer wheel
- * timer. delta_jiffies >= NEXT_TIMER_MAX_DELTA signals
- * that there is no timer pending or at least extremely
- * far into the future (12 days for HZ=1000). In this
- * case we set the expiry to the end of time.
- */
- if (likely(delta_jiffies < NEXT_TIMER_MAX_DELTA)) {
- /*
- * Calculate the time delta for the next timer event.
- * If the time delta exceeds the maximum time delta
- * permitted by the current clocksource then adjust
- * the time delta accordingly to ensure the
- * clocksource does not wrap.
- */
- time_delta = min_t(u64, time_delta,
- tick_period.tv64 * delta_jiffies);
- }
-
- if (time_delta < KTIME_MAX)
- expires = ktime_add_ns(last_update, time_delta);
- else
- expires.tv64 = KTIME_MAX;
-
- /* Skip reprogram of event if its not changed */
- if (ts->tick_stopped && ktime_equal(expires, dev->next_event))
- goto out;
+ /* Calculate the next expiry time */
+ if (delta < (KTIME_MAX - basemono))
+ expires = basemono + delta;
+ else
+ expires = KTIME_MAX;
- ret = expires;
+ expires = min_t(u64, expires, next_tick);
+ tick.tv64 = expires;
- /*
- * nohz_stop_sched_tick can be called several times before
- * the nohz_restart_sched_tick is called. This happens when
- * interrupts arrive which do not cause a reschedule. In the
- * first call we save the current tick time, so we can restart
- * the scheduler tick in nohz_restart_sched_tick.
- */
- if (!ts->tick_stopped) {
- nohz_balance_enter_idle(cpu);
- calc_load_enter_idle();
+ /* Skip reprogram of event if its not changed */
+ if (ts->tick_stopped && (expires == dev->next_event.tv64))
+ goto out;
- ts->last_tick = hrtimer_get_expires(&ts->sched_timer);
- ts->tick_stopped = 1;
- trace_tick_stop(1, " ");
- }
+ /*
+ * nohz_stop_sched_tick can be called several times before
+ * the nohz_restart_sched_tick is called. This happens when
+ * interrupts arrive which do not cause a reschedule. In the
+ * first call we save the current tick time, so we can restart
+ * the scheduler tick in nohz_restart_sched_tick.
+ */
+ if (!ts->tick_stopped) {
+ nohz_balance_enter_idle(cpu);
+ calc_load_enter_idle();
- /*
- * If the expiration time == KTIME_MAX, then
- * in this case we simply stop the tick timer.
- */
- if (unlikely(expires.tv64 == KTIME_MAX)) {
- if (ts->nohz_mode == NOHZ_MODE_HIGHRES)
- hrtimer_cancel(&ts->sched_timer);
- goto out;
- }
+ ts->last_tick = hrtimer_get_expires(&ts->sched_timer);
+ ts->tick_stopped = 1;
+ trace_tick_stop(1, " ");
+ }
- if (ts->nohz_mode == NOHZ_MODE_HIGHRES) {
- hrtimer_start(&ts->sched_timer, expires,
- HRTIMER_MODE_ABS_PINNED);
- /* Check, if the timer was already in the past */
- if (hrtimer_active(&ts->sched_timer))
- goto out;
- } else if (!tick_program_event(expires, 0))
- goto out;
- /*
- * We are past the event already. So we crossed a
- * jiffie boundary. Update jiffies and raise the
- * softirq.
- */
- tick_do_update_jiffies64(ktime_get());
+ /*
+ * If the expiration time == KTIME_MAX, then we simply stop
+ * the tick timer.
+ */
+ if (unlikely(expires == KTIME_MAX)) {
+ if (ts->nohz_mode == NOHZ_MODE_HIGHRES)
+ hrtimer_cancel(&ts->sched_timer);
+ goto out;
}
- raise_softirq_irqoff(TIMER_SOFTIRQ);
+
+ if (ts->nohz_mode == NOHZ_MODE_HIGHRES)
+ hrtimer_start(&ts->sched_timer, tick, HRTIMER_MODE_ABS_PINNED);
+ else
+ tick_program_event(tick, 1);
out:
- ts->next_jiffies = next_jiffies;
- ts->last_jiffies = last_jiffies;
+ /* Update the estimated sleep length */
ts->sleep_length = ktime_sub(dev->next_event, now);
-
- return ret;
+ return tick;
}
static void tick_nohz_full_stop_tick(struct tick_sched *ts)
@@ -876,32 +864,6 @@ ktime_t tick_nohz_get_sleep_length(void)
return ts->sleep_length;
}
-static void tick_nohz_restart(struct tick_sched *ts, ktime_t now)
-{
- hrtimer_cancel(&ts->sched_timer);
- hrtimer_set_expires(&ts->sched_timer, ts->last_tick);
-
- while (1) {
- /* Forward the time to expire in the future */
- hrtimer_forward(&ts->sched_timer, now, tick_period);
-
- if (ts->nohz_mode == NOHZ_MODE_HIGHRES) {
- hrtimer_start_expires(&ts->sched_timer,
- HRTIMER_MODE_ABS_PINNED);
- /* Check, if the timer was already in the past */
- if (hrtimer_active(&ts->sched_timer))
- break;
- } else {
- if (!tick_program_event(
- hrtimer_get_expires(&ts->sched_timer), 0))
- break;
- }
- /* Reread time and update jiffies */
- now = ktime_get();
- tick_do_update_jiffies64(now);
- }
-}
-
static void tick_nohz_restart_sched_tick(struct tick_sched *ts, ktime_t now)
{
/* Update jiffies first */
@@ -972,12 +934,6 @@ void tick_nohz_idle_exit(void)
local_irq_enable();
}
-static int tick_nohz_reprogram(struct tick_sched *ts, ktime_t now)
-{
- hrtimer_forward(&ts->sched_timer, now, tick_period);
- return tick_program_event(hrtimer_get_expires(&ts->sched_timer), 0);
-}
-
/*
* The nohz low res interrupt handler
*/
@@ -996,10 +952,18 @@ static void tick_nohz_handler(struct clock_event_device *dev)
if (unlikely(ts->tick_stopped))
return;
- while (tick_nohz_reprogram(ts, now)) {
- now = ktime_get();
- tick_do_update_jiffies64(now);
- }
+ hrtimer_forward(&ts->sched_timer, now, tick_period);
+ tick_program_event(hrtimer_get_expires(&ts->sched_timer), 1);
+}
+
+static inline void tick_nohz_activate(struct tick_sched *ts, int mode)
+{
+ if (!tick_nohz_enabled)
+ return;
+ ts->nohz_mode = mode;
+ /* One update is enough */
+ if (!test_and_set_bit(0, &tick_nohz_active))
+ timers_update_migration(true);
}
/**
@@ -1013,13 +977,8 @@ static void tick_nohz_switch_to_nohz(void)
if (!tick_nohz_enabled)
return;
- local_irq_disable();
- if (tick_switch_to_oneshot(tick_nohz_handler)) {
- local_irq_enable();
+ if (tick_switch_to_oneshot(tick_nohz_handler))
return;
- }
- tick_nohz_active = 1;
- ts->nohz_mode = NOHZ_MODE_LOWRES;
/*
* Recycle the hrtimer in ts, so we can share the
@@ -1029,13 +988,10 @@ static void tick_nohz_switch_to_nohz(void)
/* Get the next period */
next = tick_init_jiffy_update();
- for (;;) {
- hrtimer_set_expires(&ts->sched_timer, next);
- if (!tick_program_event(next, 0))
- break;
- next = ktime_add(next, tick_period);
- }
- local_irq_enable();
+ hrtimer_forward_now(&ts->sched_timer, tick_period);
+ hrtimer_set_expires(&ts->sched_timer, next);
+ tick_program_event(next, 1);
+ tick_nohz_activate(ts, NOHZ_MODE_LOWRES);
}
/*
@@ -1087,6 +1043,7 @@ static inline void tick_nohz_irq_enter(void)
static inline void tick_nohz_switch_to_nohz(void) { }
static inline void tick_nohz_irq_enter(void) { }
+static inline void tick_nohz_activate(struct tick_sched *ts, int mode) { }
#endif /* CONFIG_NO_HZ_COMMON */
@@ -1167,22 +1124,9 @@ void tick_setup_sched_timer(void)
hrtimer_add_expires_ns(&ts->sched_timer, offset);
}
- for (;;) {
- hrtimer_forward(&ts->sched_timer, now, tick_period);
- hrtimer_start_expires(&ts->sched_timer,
- HRTIMER_MODE_ABS_PINNED);
- /* Check, if the timer was already in the past */
- if (hrtimer_active(&ts->sched_timer))
- break;
- now = ktime_get();
- }
-
-#ifdef CONFIG_NO_HZ_COMMON
- if (tick_nohz_enabled) {
- ts->nohz_mode = NOHZ_MODE_HIGHRES;
- tick_nohz_active = 1;
- }
-#endif
+ hrtimer_forward(&ts->sched_timer, now, tick_period);
+ hrtimer_start_expires(&ts->sched_timer, HRTIMER_MODE_ABS_PINNED);
+ tick_nohz_activate(ts, NOHZ_MODE_HIGHRES);
}
#endif /* HIGH_RES_TIMERS */
@@ -1227,7 +1171,7 @@ void tick_oneshot_notify(void)
* Called cyclic from the hrtimer softirq (driven by the timer
* softirq) allow_nohz signals, that we can switch into low-res nohz
* mode, because high resolution timers are disabled (either compile
- * or runtime).
+ * or runtime). Called with interrupts disabled.
*/
int tick_check_oneshot_change(int allow_nohz)
{