|
|
@@ -0,0 +1,558 @@
|
|
|
+/*
|
|
|
+ * linux/kernel/time/tick-sched.c
|
|
|
+ *
|
|
|
+ * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
|
|
|
+ * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
|
|
|
+ * Copyright(C) 2006-2007 Timesys Corp., Thomas Gleixner
|
|
|
+ *
|
|
|
+ * No idle tick implementation for low and high resolution timers
|
|
|
+ *
|
|
|
+ * Started by: Thomas Gleixner and Ingo Molnar
|
|
|
+ *
|
|
|
+ * For licencing details see kernel-base/COPYING
|
|
|
+ */
|
|
|
+#include <linux/cpu.h>
|
|
|
+#include <linux/err.h>
|
|
|
+#include <linux/hrtimer.h>
|
|
|
+#include <linux/interrupt.h>
|
|
|
+#include <linux/kernel_stat.h>
|
|
|
+#include <linux/percpu.h>
|
|
|
+#include <linux/profile.h>
|
|
|
+#include <linux/sched.h>
|
|
|
+#include <linux/tick.h>
|
|
|
+
|
|
|
+#include "tick-internal.h"
|
|
|
+
|
|
|
+/*
|
|
|
+ * Per cpu nohz control structure
|
|
|
+ */
|
|
|
+static DEFINE_PER_CPU(struct tick_sched, tick_cpu_sched);
|
|
|
+
|
|
|
+/*
|
|
|
+ * The time, when the last jiffy update happened. Protected by xtime_lock.
|
|
|
+ */
|
|
|
+static ktime_t last_jiffies_update;
|
|
|
+
|
|
|
+/*
|
|
|
+ * Must be called with interrupts disabled !
|
|
|
+ */
|
|
|
+static void tick_do_update_jiffies64(ktime_t now)
|
|
|
+{
|
|
|
+ unsigned long ticks = 0;
|
|
|
+ ktime_t delta;
|
|
|
+
|
|
|
+ /* Reevalute with xtime_lock held */
|
|
|
+ write_seqlock(&xtime_lock);
|
|
|
+
|
|
|
+ delta = ktime_sub(now, last_jiffies_update);
|
|
|
+ if (delta.tv64 >= tick_period.tv64) {
|
|
|
+
|
|
|
+ delta = ktime_sub(delta, tick_period);
|
|
|
+ last_jiffies_update = ktime_add(last_jiffies_update,
|
|
|
+ tick_period);
|
|
|
+
|
|
|
+ /* Slow path for long timeouts */
|
|
|
+ if (unlikely(delta.tv64 >= tick_period.tv64)) {
|
|
|
+ s64 incr = ktime_to_ns(tick_period);
|
|
|
+
|
|
|
+ ticks = ktime_divns(delta, incr);
|
|
|
+
|
|
|
+ last_jiffies_update = ktime_add_ns(last_jiffies_update,
|
|
|
+ incr * ticks);
|
|
|
+ }
|
|
|
+ do_timer(++ticks);
|
|
|
+ }
|
|
|
+ write_sequnlock(&xtime_lock);
|
|
|
+}
|
|
|
+
|
|
|
+/*
|
|
|
+ * Initialize and return retrieve the jiffies update.
|
|
|
+ */
|
|
|
+static ktime_t tick_init_jiffy_update(void)
|
|
|
+{
|
|
|
+ ktime_t period;
|
|
|
+
|
|
|
+ write_seqlock(&xtime_lock);
|
|
|
+ /* Did we start the jiffies update yet ? */
|
|
|
+ if (last_jiffies_update.tv64 == 0)
|
|
|
+ last_jiffies_update = tick_next_period;
|
|
|
+ period = last_jiffies_update;
|
|
|
+ write_sequnlock(&xtime_lock);
|
|
|
+ return period;
|
|
|
+}
|
|
|
+
|
|
|
+/*
|
|
|
+ * NOHZ - aka dynamic tick functionality
|
|
|
+ */
|
|
|
+#ifdef CONFIG_NO_HZ
|
|
|
+/*
|
|
|
+ * NO HZ enabled ?
|
|
|
+ */
|
|
|
+static int tick_nohz_enabled __read_mostly = 1;
|
|
|
+
|
|
|
+/*
|
|
|
+ * Enable / Disable tickless mode
|
|
|
+ */
|
|
|
+static int __init setup_tick_nohz(char *str)
|
|
|
+{
|
|
|
+ if (!strcmp(str, "off"))
|
|
|
+ tick_nohz_enabled = 0;
|
|
|
+ else if (!strcmp(str, "on"))
|
|
|
+ tick_nohz_enabled = 1;
|
|
|
+ else
|
|
|
+ return 0;
|
|
|
+ return 1;
|
|
|
+}
|
|
|
+
|
|
|
+__setup("nohz=", setup_tick_nohz);
|
|
|
+
|
|
|
+/**
|
|
|
+ * tick_nohz_update_jiffies - update jiffies when idle was interrupted
|
|
|
+ *
|
|
|
+ * Called from interrupt entry when the CPU was idle
|
|
|
+ *
|
|
|
+ * In case the sched_tick was stopped on this CPU, we have to check if jiffies
|
|
|
+ * must be updated. Otherwise an interrupt handler could use a stale jiffy
|
|
|
+ * value. We do this unconditionally on any cpu, as we don't know whether the
|
|
|
+ * cpu, which has the update task assigned is in a long sleep.
|
|
|
+ */
|
|
|
+void tick_nohz_update_jiffies(void)
|
|
|
+{
|
|
|
+ int cpu = smp_processor_id();
|
|
|
+ struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
|
|
|
+ unsigned long flags;
|
|
|
+ ktime_t now;
|
|
|
+
|
|
|
+ if (!ts->tick_stopped)
|
|
|
+ return;
|
|
|
+
|
|
|
+ cpu_clear(cpu, nohz_cpu_mask);
|
|
|
+ now = ktime_get();
|
|
|
+
|
|
|
+ local_irq_save(flags);
|
|
|
+ tick_do_update_jiffies64(now);
|
|
|
+ local_irq_restore(flags);
|
|
|
+}
|
|
|
+
|
|
|
+/**
|
|
|
+ * tick_nohz_stop_sched_tick - stop the idle tick from the idle task
|
|
|
+ *
|
|
|
+ * When the next event is more than a tick into the future, stop the idle tick
|
|
|
+ * Called either from the idle loop or from irq_exit() when an idle period was
|
|
|
+ * just interrupted by an interrupt which did not cause a reschedule.
|
|
|
+ */
|
|
|
+void tick_nohz_stop_sched_tick(void)
|
|
|
+{
|
|
|
+ unsigned long seq, last_jiffies, next_jiffies, delta_jiffies, flags;
|
|
|
+ struct tick_sched *ts;
|
|
|
+ ktime_t last_update, expires, now, delta;
|
|
|
+ int cpu;
|
|
|
+
|
|
|
+ local_irq_save(flags);
|
|
|
+
|
|
|
+ cpu = smp_processor_id();
|
|
|
+ ts = &per_cpu(tick_cpu_sched, cpu);
|
|
|
+
|
|
|
+ if (unlikely(ts->nohz_mode == NOHZ_MODE_INACTIVE))
|
|
|
+ goto end;
|
|
|
+
|
|
|
+ if (need_resched())
|
|
|
+ goto end;
|
|
|
+
|
|
|
+ cpu = smp_processor_id();
|
|
|
+ BUG_ON(local_softirq_pending());
|
|
|
+
|
|
|
+ now = ktime_get();
|
|
|
+ /*
|
|
|
+ * When called from irq_exit we need to account the idle sleep time
|
|
|
+ * correctly.
|
|
|
+ */
|
|
|
+ if (ts->tick_stopped) {
|
|
|
+ delta = ktime_sub(now, ts->idle_entrytime);
|
|
|
+ ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta);
|
|
|
+ }
|
|
|
+
|
|
|
+ ts->idle_entrytime = now;
|
|
|
+ ts->idle_calls++;
|
|
|
+
|
|
|
+ /* Read jiffies and the time when jiffies were updated last */
|
|
|
+ do {
|
|
|
+ seq = read_seqbegin(&xtime_lock);
|
|
|
+ last_update = last_jiffies_update;
|
|
|
+ last_jiffies = jiffies;
|
|
|
+ } while (read_seqretry(&xtime_lock, seq));
|
|
|
+
|
|
|
+ /* Get the next timer wheel timer */
|
|
|
+ next_jiffies = get_next_timer_interrupt(last_jiffies);
|
|
|
+ delta_jiffies = next_jiffies - last_jiffies;
|
|
|
+
|
|
|
+ /*
|
|
|
+ * Do not stop the tick, if we are only one off
|
|
|
+ * or if the cpu is required for rcu
|
|
|
+ */
|
|
|
+ if (!ts->tick_stopped && (delta_jiffies == 1 || rcu_needs_cpu(cpu)))
|
|
|
+ goto out;
|
|
|
+
|
|
|
+ /* Schedule the tick, if we are at least one jiffie off */
|
|
|
+ if ((long)delta_jiffies >= 1) {
|
|
|
+
|
|
|
+ if (rcu_needs_cpu(cpu))
|
|
|
+ delta_jiffies = 1;
|
|
|
+ else
|
|
|
+ cpu_set(cpu, nohz_cpu_mask);
|
|
|
+ /*
|
|
|
+ * 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) {
|
|
|
+ ts->idle_tick = ts->sched_timer.expires;
|
|
|
+ ts->tick_stopped = 1;
|
|
|
+ ts->idle_jiffies = last_jiffies;
|
|
|
+ }
|
|
|
+ /*
|
|
|
+ * calculate the expiry time for the next timer wheel
|
|
|
+ * timer
|
|
|
+ */
|
|
|
+ expires = ktime_add_ns(last_update, tick_period.tv64 *
|
|
|
+ delta_jiffies);
|
|
|
+ ts->idle_expires = expires;
|
|
|
+ ts->idle_sleeps++;
|
|
|
+
|
|
|
+ if (ts->nohz_mode == NOHZ_MODE_HIGHRES) {
|
|
|
+ hrtimer_start(&ts->sched_timer, expires,
|
|
|
+ HRTIMER_MODE_ABS);
|
|
|
+ /* 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());
|
|
|
+ cpu_clear(cpu, nohz_cpu_mask);
|
|
|
+ }
|
|
|
+ raise_softirq_irqoff(TIMER_SOFTIRQ);
|
|
|
+out:
|
|
|
+ ts->next_jiffies = next_jiffies;
|
|
|
+ ts->last_jiffies = last_jiffies;
|
|
|
+end:
|
|
|
+ local_irq_restore(flags);
|
|
|
+}
|
|
|
+
|
|
|
+/**
|
|
|
+ * nohz_restart_sched_tick - restart the idle tick from the idle task
|
|
|
+ *
|
|
|
+ * Restart the idle tick when the CPU is woken up from idle
|
|
|
+ */
|
|
|
+void tick_nohz_restart_sched_tick(void)
|
|
|
+{
|
|
|
+ int cpu = smp_processor_id();
|
|
|
+ struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
|
|
|
+ unsigned long ticks;
|
|
|
+ ktime_t now, delta;
|
|
|
+
|
|
|
+ if (!ts->tick_stopped)
|
|
|
+ return;
|
|
|
+
|
|
|
+ /* Update jiffies first */
|
|
|
+ now = ktime_get();
|
|
|
+
|
|
|
+ local_irq_disable();
|
|
|
+ tick_do_update_jiffies64(now);
|
|
|
+ cpu_clear(cpu, nohz_cpu_mask);
|
|
|
+
|
|
|
+ /* Account the idle time */
|
|
|
+ delta = ktime_sub(now, ts->idle_entrytime);
|
|
|
+ ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta);
|
|
|
+
|
|
|
+ /*
|
|
|
+ * We stopped the tick in idle. Update process times would miss the
|
|
|
+ * time we slept as update_process_times does only a 1 tick
|
|
|
+ * accounting. Enforce that this is accounted to idle !
|
|
|
+ */
|
|
|
+ ticks = jiffies - ts->idle_jiffies;
|
|
|
+ /*
|
|
|
+ * We might be one off. Do not randomly account a huge number of ticks!
|
|
|
+ */
|
|
|
+ if (ticks && ticks < LONG_MAX) {
|
|
|
+ add_preempt_count(HARDIRQ_OFFSET);
|
|
|
+ account_system_time(current, HARDIRQ_OFFSET,
|
|
|
+ jiffies_to_cputime(ticks));
|
|
|
+ sub_preempt_count(HARDIRQ_OFFSET);
|
|
|
+ }
|
|
|
+
|
|
|
+ /*
|
|
|
+ * Cancel the scheduled timer and restore the tick
|
|
|
+ */
|
|
|
+ ts->tick_stopped = 0;
|
|
|
+ hrtimer_cancel(&ts->sched_timer);
|
|
|
+ ts->sched_timer.expires = ts->idle_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(&ts->sched_timer,
|
|
|
+ ts->sched_timer.expires,
|
|
|
+ HRTIMER_MODE_ABS);
|
|
|
+ /* Check, if the timer was already in the past */
|
|
|
+ if (hrtimer_active(&ts->sched_timer))
|
|
|
+ break;
|
|
|
+ } else {
|
|
|
+ if (!tick_program_event(ts->sched_timer.expires, 0))
|
|
|
+ break;
|
|
|
+ }
|
|
|
+ /* Update jiffies and reread time */
|
|
|
+ tick_do_update_jiffies64(now);
|
|
|
+ now = ktime_get();
|
|
|
+ }
|
|
|
+ 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(ts->sched_timer.expires, 0);
|
|
|
+}
|
|
|
+
|
|
|
+/*
|
|
|
+ * The nohz low res interrupt handler
|
|
|
+ */
|
|
|
+static void tick_nohz_handler(struct clock_event_device *dev)
|
|
|
+{
|
|
|
+ struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
|
|
|
+ struct pt_regs *regs = get_irq_regs();
|
|
|
+ ktime_t now = ktime_get();
|
|
|
+
|
|
|
+ dev->next_event.tv64 = KTIME_MAX;
|
|
|
+
|
|
|
+ /* Check, if the jiffies need an update */
|
|
|
+ tick_do_update_jiffies64(now);
|
|
|
+
|
|
|
+ /*
|
|
|
+ * When we are idle and the tick is stopped, we have to touch
|
|
|
+ * the watchdog as we might not schedule for a really long
|
|
|
+ * time. This happens on complete idle SMP systems while
|
|
|
+ * waiting on the login prompt. We also increment the "start
|
|
|
+ * of idle" jiffy stamp so the idle accounting adjustment we
|
|
|
+ * do when we go busy again does not account too much ticks.
|
|
|
+ */
|
|
|
+ if (ts->tick_stopped) {
|
|
|
+ touch_softlockup_watchdog();
|
|
|
+ ts->idle_jiffies++;
|
|
|
+ }
|
|
|
+
|
|
|
+ update_process_times(user_mode(regs));
|
|
|
+ profile_tick(CPU_PROFILING);
|
|
|
+
|
|
|
+ /* Do not restart, when we are in the idle loop */
|
|
|
+ if (ts->tick_stopped)
|
|
|
+ return;
|
|
|
+
|
|
|
+ while (tick_nohz_reprogram(ts, now)) {
|
|
|
+ now = ktime_get();
|
|
|
+ tick_do_update_jiffies64(now);
|
|
|
+ }
|
|
|
+}
|
|
|
+
|
|
|
+/**
|
|
|
+ * tick_nohz_switch_to_nohz - switch to nohz mode
|
|
|
+ */
|
|
|
+static void tick_nohz_switch_to_nohz(void)
|
|
|
+{
|
|
|
+ struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
|
|
|
+ ktime_t next;
|
|
|
+
|
|
|
+ if (!tick_nohz_enabled)
|
|
|
+ return;
|
|
|
+
|
|
|
+ local_irq_disable();
|
|
|
+ if (tick_switch_to_oneshot(tick_nohz_handler)) {
|
|
|
+ local_irq_enable();
|
|
|
+ return;
|
|
|
+ }
|
|
|
+
|
|
|
+ ts->nohz_mode = NOHZ_MODE_LOWRES;
|
|
|
+
|
|
|
+ /*
|
|
|
+ * Recycle the hrtimer in ts, so we can share the
|
|
|
+ * hrtimer_forward with the highres code.
|
|
|
+ */
|
|
|
+ hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
|
|
|
+ /* Get the next period */
|
|
|
+ next = tick_init_jiffy_update();
|
|
|
+
|
|
|
+ for (;;) {
|
|
|
+ ts->sched_timer.expires = next;
|
|
|
+ if (!tick_program_event(next, 0))
|
|
|
+ break;
|
|
|
+ next = ktime_add(next, tick_period);
|
|
|
+ }
|
|
|
+ local_irq_enable();
|
|
|
+
|
|
|
+ printk(KERN_INFO "Switched to NOHz mode on CPU #%d\n",
|
|
|
+ smp_processor_id());
|
|
|
+}
|
|
|
+
|
|
|
+#else
|
|
|
+
|
|
|
+static inline void tick_nohz_switch_to_nohz(void) { }
|
|
|
+
|
|
|
+#endif /* NO_HZ */
|
|
|
+
|
|
|
+/*
|
|
|
+ * High resolution timer specific code
|
|
|
+ */
|
|
|
+#ifdef CONFIG_HIGH_RES_TIMERS
|
|
|
+/*
|
|
|
+ * We rearm the timer until we get disabled by the idle code
|
|
|
+ * Called with interrupts disabled and timer->base->cpu_base->lock held.
|
|
|
+ */
|
|
|
+static enum hrtimer_restart tick_sched_timer(struct hrtimer *timer)
|
|
|
+{
|
|
|
+ struct tick_sched *ts =
|
|
|
+ container_of(timer, struct tick_sched, sched_timer);
|
|
|
+ struct hrtimer_cpu_base *base = timer->base->cpu_base;
|
|
|
+ struct pt_regs *regs = get_irq_regs();
|
|
|
+ ktime_t now = ktime_get();
|
|
|
+
|
|
|
+ /* Check, if the jiffies need an update */
|
|
|
+ tick_do_update_jiffies64(now);
|
|
|
+
|
|
|
+ /*
|
|
|
+ * Do not call, when we are not in irq context and have
|
|
|
+ * no valid regs pointer
|
|
|
+ */
|
|
|
+ if (regs) {
|
|
|
+ /*
|
|
|
+ * When we are idle and the tick is stopped, we have to touch
|
|
|
+ * the watchdog as we might not schedule for a really long
|
|
|
+ * time. This happens on complete idle SMP systems while
|
|
|
+ * waiting on the login prompt. We also increment the "start of
|
|
|
+ * idle" jiffy stamp so the idle accounting adjustment we do
|
|
|
+ * when we go busy again does not account too much ticks.
|
|
|
+ */
|
|
|
+ if (ts->tick_stopped) {
|
|
|
+ touch_softlockup_watchdog();
|
|
|
+ ts->idle_jiffies++;
|
|
|
+ }
|
|
|
+ /*
|
|
|
+ * update_process_times() might take tasklist_lock, hence
|
|
|
+ * drop the base lock. sched-tick hrtimers are per-CPU and
|
|
|
+ * never accessible by userspace APIs, so this is safe to do.
|
|
|
+ */
|
|
|
+ spin_unlock(&base->lock);
|
|
|
+ update_process_times(user_mode(regs));
|
|
|
+ profile_tick(CPU_PROFILING);
|
|
|
+ spin_lock(&base->lock);
|
|
|
+ }
|
|
|
+
|
|
|
+ /* Do not restart, when we are in the idle loop */
|
|
|
+ if (ts->tick_stopped)
|
|
|
+ return HRTIMER_NORESTART;
|
|
|
+
|
|
|
+ hrtimer_forward(timer, now, tick_period);
|
|
|
+
|
|
|
+ return HRTIMER_RESTART;
|
|
|
+}
|
|
|
+
|
|
|
+/**
|
|
|
+ * tick_setup_sched_timer - setup the tick emulation timer
|
|
|
+ */
|
|
|
+void tick_setup_sched_timer(void)
|
|
|
+{
|
|
|
+ struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
|
|
|
+ ktime_t now = ktime_get();
|
|
|
+
|
|
|
+ /*
|
|
|
+ * Emulate tick processing via per-CPU hrtimers:
|
|
|
+ */
|
|
|
+ hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
|
|
|
+ ts->sched_timer.function = tick_sched_timer;
|
|
|
+ ts->sched_timer.cb_mode = HRTIMER_CB_IRQSAFE_NO_SOFTIRQ;
|
|
|
+
|
|
|
+ /* Get the next period */
|
|
|
+ ts->sched_timer.expires = tick_init_jiffy_update();
|
|
|
+
|
|
|
+ for (;;) {
|
|
|
+ hrtimer_forward(&ts->sched_timer, now, tick_period);
|
|
|
+ hrtimer_start(&ts->sched_timer, ts->sched_timer.expires,
|
|
|
+ HRTIMER_MODE_ABS);
|
|
|
+ /* Check, if the timer was already in the past */
|
|
|
+ if (hrtimer_active(&ts->sched_timer))
|
|
|
+ break;
|
|
|
+ now = ktime_get();
|
|
|
+ }
|
|
|
+
|
|
|
+#ifdef CONFIG_NO_HZ
|
|
|
+ if (tick_nohz_enabled)
|
|
|
+ ts->nohz_mode = NOHZ_MODE_HIGHRES;
|
|
|
+#endif
|
|
|
+}
|
|
|
+
|
|
|
+void tick_cancel_sched_timer(int cpu)
|
|
|
+{
|
|
|
+ struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
|
|
|
+
|
|
|
+ if (ts->sched_timer.base)
|
|
|
+ hrtimer_cancel(&ts->sched_timer);
|
|
|
+ ts->tick_stopped = 0;
|
|
|
+ ts->nohz_mode = NOHZ_MODE_INACTIVE;
|
|
|
+}
|
|
|
+#endif /* HIGH_RES_TIMERS */
|
|
|
+
|
|
|
+/**
|
|
|
+ * Async notification about clocksource changes
|
|
|
+ */
|
|
|
+void tick_clock_notify(void)
|
|
|
+{
|
|
|
+ int cpu;
|
|
|
+
|
|
|
+ for_each_possible_cpu(cpu)
|
|
|
+ set_bit(0, &per_cpu(tick_cpu_sched, cpu).check_clocks);
|
|
|
+}
|
|
|
+
|
|
|
+/*
|
|
|
+ * Async notification about clock event changes
|
|
|
+ */
|
|
|
+void tick_oneshot_notify(void)
|
|
|
+{
|
|
|
+ struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
|
|
|
+
|
|
|
+ set_bit(0, &ts->check_clocks);
|
|
|
+}
|
|
|
+
|
|
|
+/**
|
|
|
+ * Check, if a change happened, which makes oneshot possible.
|
|
|
+ *
|
|
|
+ * 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).
|
|
|
+ */
|
|
|
+int tick_check_oneshot_change(int allow_nohz)
|
|
|
+{
|
|
|
+ struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
|
|
|
+
|
|
|
+ if (!test_and_clear_bit(0, &ts->check_clocks))
|
|
|
+ return 0;
|
|
|
+
|
|
|
+ if (ts->nohz_mode != NOHZ_MODE_INACTIVE)
|
|
|
+ return 0;
|
|
|
+
|
|
|
+ if (!timekeeping_is_continuous() || !tick_is_oneshot_available())
|
|
|
+ return 0;
|
|
|
+
|
|
|
+ if (!allow_nohz)
|
|
|
+ return 1;
|
|
|
+
|
|
|
+ tick_nohz_switch_to_nohz();
|
|
|
+ return 0;
|
|
|
+}
|
Thomas Gleixner