*
* Started by: Thomas Gleixner and Ingo Molnar
*
- * For licencing details see kernel-base/COPYING
+ * Distribute under GPLv2.
*/
#include <linux/cpu.h>
#include <linux/err.h>
#include <linux/profile.h>
#include <linux/sched.h>
#include <linux/tick.h>
+#include <linux/module.h>
#include <asm/irq_regs.h>
unsigned long ticks = 0;
ktime_t delta;
+ /*
+ * Do a quick check without holding xtime_lock:
+ */
+ delta = ktime_sub(now, last_jiffies_update);
+ if (delta.tv64 < tick_period.tv64)
+ return;
+
/* Reevalute with xtime_lock held */
write_seqlock(&xtime_lock);
incr * ticks);
}
do_timer(++ticks);
+
+ /* Keep the tick_next_period variable up to date */
+ tick_next_period = ktime_add(last_jiffies_update, tick_period);
}
write_sequnlock(&xtime_lock);
}
* 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)
+static void tick_nohz_update_jiffies(void)
{
int cpu = smp_processor_id();
struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
if (!ts->tick_stopped)
return;
- cpu_clear(cpu, nohz_cpu_mask);
+ cpumask_clear_cpu(cpu, nohz_cpu_mask);
now = ktime_get();
+ ts->idle_waketime = now;
local_irq_save(flags);
tick_do_update_jiffies64(now);
local_irq_restore(flags);
+
+ touch_softlockup_watchdog();
+}
+
+static void tick_nohz_stop_idle(int cpu)
+{
+ struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
+
+ if (ts->idle_active) {
+ ktime_t now, delta;
+ now = ktime_get();
+ delta = ktime_sub(now, ts->idle_entrytime);
+ ts->idle_lastupdate = now;
+ ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta);
+ ts->idle_active = 0;
+
+ sched_clock_idle_wakeup_event(0);
+ }
+}
+
+static ktime_t tick_nohz_start_idle(struct tick_sched *ts)
+{
+ ktime_t now, delta;
+
+ now = ktime_get();
+ if (ts->idle_active) {
+ delta = ktime_sub(now, ts->idle_entrytime);
+ ts->idle_lastupdate = now;
+ ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta);
+ }
+ ts->idle_entrytime = now;
+ ts->idle_active = 1;
+ sched_clock_idle_sleep_event();
+ return now;
}
+u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time)
+{
+ struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
+
+ if (!tick_nohz_enabled)
+ return -1;
+
+ if (ts->idle_active)
+ *last_update_time = ktime_to_us(ts->idle_lastupdate);
+ else
+ *last_update_time = ktime_to_us(ktime_get());
+
+ return ktime_to_us(ts->idle_sleeptime);
+}
+EXPORT_SYMBOL_GPL(get_cpu_idle_time_us);
+
/**
* tick_nohz_stop_sched_tick - stop the idle tick from the idle task
*
* 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)
+void tick_nohz_stop_sched_tick(int inidle)
{
unsigned long seq, last_jiffies, next_jiffies, delta_jiffies, flags;
struct tick_sched *ts;
- ktime_t last_update, expires, now, delta;
+ ktime_t last_update, expires, now;
+ struct clock_event_device *dev = __get_cpu_var(tick_cpu_device).evtdev;
int cpu;
local_irq_save(flags);
cpu = smp_processor_id();
ts = &per_cpu(tick_cpu_sched, cpu);
+ now = tick_nohz_start_idle(ts);
+
+ /*
+ * If this cpu is offline and it 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. If we don't drop
+ * this here the jiffies might be stale and do_timer() never
+ * invoked.
+ */
+ if (unlikely(!cpu_online(cpu))) {
+ if (cpu == tick_do_timer_cpu)
+ tick_do_timer_cpu = TICK_DO_TIMER_NONE;
+ }
if (unlikely(ts->nohz_mode == NOHZ_MODE_INACTIVE))
goto end;
+ if (!inidle && !ts->inidle)
+ goto end;
+
+ ts->inidle = 1;
+
if (need_resched())
goto end;
- cpu = smp_processor_id();
- if (unlikely(local_softirq_pending()))
- printk(KERN_ERR "NOHZ: local_softirq_pending %02x\n",
- local_softirq_pending());
+ if (unlikely(local_softirq_pending() && cpu_online(cpu))) {
+ static int ratelimit;
- 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);
+ if (ratelimit < 10) {
+ printk(KERN_ERR "NOHZ: local_softirq_pending %02x\n",
+ local_softirq_pending());
+ ratelimit++;
+ }
+ goto end;
}
- ts->idle_entrytime = now;
ts->idle_calls++;
-
/* Read jiffies and the time when jiffies were updated last */
do {
seq = read_seqbegin(&xtime_lock);
next_jiffies = get_next_timer_interrupt(last_jiffies);
delta_jiffies = next_jiffies - last_jiffies;
- if (rcu_needs_cpu(cpu))
+ if (rcu_needs_cpu(cpu) || printk_needs_cpu(cpu))
delta_jiffies = 1;
/*
* Do not stop the tick, if we are only one off
/* Schedule the tick, if we are at least one jiffie off */
if ((long)delta_jiffies >= 1) {
+ /*
+ * calculate the expiry time for the next timer wheel
+ * timer
+ */
+ expires = ktime_add_ns(last_update, tick_period.tv64 *
+ delta_jiffies);
+
+ /*
+ * 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.
+ */
+ if (cpu == tick_do_timer_cpu)
+ tick_do_timer_cpu = TICK_DO_TIMER_NONE;
+
if (delta_jiffies > 1)
- cpu_set(cpu, nohz_cpu_mask);
+ cpumask_set_cpu(cpu, nohz_cpu_mask);
+
+ /* Skip reprogram of event if its not changed */
+ if (ts->tick_stopped && ktime_equal(expires, dev->next_event))
+ goto out;
+
/*
* nohz_stop_sched_tick can be called several times before
* the nohz_restart_sched_tick is called. This happens when
* the scheduler tick in nohz_restart_sched_tick.
*/
if (!ts->tick_stopped) {
- ts->idle_tick = ts->sched_timer.expires;
+ if (select_nohz_load_balancer(1)) {
+ /*
+ * sched tick not stopped!
+ */
+ cpumask_clear_cpu(cpu, nohz_cpu_mask);
+ goto out;
+ }
+
+ ts->idle_tick = hrtimer_get_expires(&ts->sched_timer);
ts->tick_stopped = 1;
ts->idle_jiffies = last_jiffies;
+ rcu_enter_nohz();
}
- /*
- * 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.
- */
- if (cpu == tick_do_timer_cpu)
- tick_do_timer_cpu = -1;
+ ts->idle_sleeps++;
/*
- * 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 extremly far
+ * into the future (12 days for HZ=1000). In this case
+ * we simply stop the tick timer:
*/
- expires = ktime_add_ns(last_update, tick_period.tv64 *
- delta_jiffies);
+ if (unlikely(delta_jiffies >= NEXT_TIMER_MAX_DELTA)) {
+ ts->idle_expires.tv64 = KTIME_MAX;
+ if (ts->nohz_mode == NOHZ_MODE_HIGHRES)
+ hrtimer_cancel(&ts->sched_timer);
+ goto out;
+ }
+
+ /* Mark expiries */
ts->idle_expires = expires;
- ts->idle_sleeps++;
if (ts->nohz_mode == NOHZ_MODE_HIGHRES) {
hrtimer_start(&ts->sched_timer, expires,
/* Check, if the timer was already in the past */
if (hrtimer_active(&ts->sched_timer))
goto out;
- } else if(!tick_program_event(expires, 0))
+ } else if (!tick_program_event(expires, 0))
goto out;
/*
* We are past the event already. So we crossed a
* softirq.
*/
tick_do_update_jiffies64(ktime_get());
- cpu_clear(cpu, nohz_cpu_mask);
+ cpumask_clear_cpu(cpu, nohz_cpu_mask);
}
raise_softirq_irqoff(TIMER_SOFTIRQ);
out:
ts->next_jiffies = next_jiffies;
ts->last_jiffies = last_jiffies;
+ ts->sleep_length = ktime_sub(dev->next_event, now);
end:
local_irq_restore(flags);
}
/**
- * nohz_restart_sched_tick - restart the idle tick from the idle task
+ * tick_nohz_get_sleep_length - return the length of the current sleep
+ *
+ * Called from power state control code with interrupts disabled
+ */
+ktime_t tick_nohz_get_sleep_length(void)
+{
+ struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
+
+ 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->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_expires(&ts->sched_timer,
+ HRTIMER_MODE_ABS);
+ /* 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;
+ }
+ /* Update jiffies and reread time */
+ tick_do_update_jiffies64(now);
+ now = ktime_get();
+ }
+}
+
+/**
+ * tick_nohz_restart_sched_tick - restart the idle tick from the idle task
*
* Restart the idle tick when the CPU is woken up from idle
*/
{
int cpu = smp_processor_id();
struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
+#ifndef CONFIG_VIRT_CPU_ACCOUNTING
unsigned long ticks;
- ktime_t now, delta;
+#endif
+ ktime_t now;
- if (!ts->tick_stopped)
+ local_irq_disable();
+ tick_nohz_stop_idle(cpu);
+
+ if (!ts->inidle || !ts->tick_stopped) {
+ ts->inidle = 0;
+ local_irq_enable();
return;
+ }
+
+ ts->inidle = 0;
+
+ rcu_exit_nohz();
/* Update jiffies first */
+ select_nohz_load_balancer(0);
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);
+ cpumask_clear_cpu(cpu, nohz_cpu_mask);
+#ifndef CONFIG_VIRT_CPU_ACCOUNTING
/*
* We stopped the tick in idle. Update process times would miss the
* time we slept as update_process_times does only a 1 tick
/*
* 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);
- }
+ if (ticks && ticks < LONG_MAX)
+ account_idle_ticks(ticks);
+#endif
+ touch_softlockup_watchdog();
/*
* Cancel the scheduled timer and restore the tick
*/
ts->tick_stopped = 0;
- hrtimer_cancel(&ts->sched_timer);
- ts->sched_timer.expires = ts->idle_tick;
+ ts->idle_exittime = now;
- while (1) {
- /* Forward the time to expire in the future */
- hrtimer_forward(&ts->sched_timer, now, tick_period);
+ tick_nohz_restart(ts, now);
- 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);
+ return tick_program_event(hrtimer_get_expires(&ts->sched_timer), 0);
}
/*
* this duty, then the jiffies update is still serialized by
* xtime_lock.
*/
- if (unlikely(tick_do_timer_cpu == -1))
+ if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE))
tick_do_timer_cpu = cpu;
/* Check, if the jiffies need an update */
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);
next = tick_init_jiffy_update();
for (;;) {
- ts->sched_timer.expires = next;
+ hrtimer_set_expires(&ts->sched_timer, next);
if (!tick_program_event(next, 0))
break;
next = ktime_add(next, tick_period);
smp_processor_id());
}
+/*
+ * When NOHZ is enabled and the tick is stopped, we need to kick the
+ * tick timer from irq_enter() so that the jiffies update is kept
+ * alive during long running softirqs. That's ugly as hell, but
+ * correctness is key even if we need to fix the offending softirq in
+ * the first place.
+ *
+ * Note, this is different to tick_nohz_restart. We just kick the
+ * timer and do not touch the other magic bits which need to be done
+ * when idle is left.
+ */
+static void tick_nohz_kick_tick(int cpu)
+{
+#if 0
+ /* Switch back to 2.6.27 behaviour */
+
+ struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
+ ktime_t delta, now;
+
+ if (!ts->tick_stopped)
+ return;
+
+ /*
+ * Do not touch the tick device, when the next expiry is either
+ * already reached or less/equal than the tick period.
+ */
+ now = ktime_get();
+ delta = ktime_sub(hrtimer_get_expires(&ts->sched_timer), now);
+ if (delta.tv64 <= tick_period.tv64)
+ return;
+
+ tick_nohz_restart(ts, now);
+#endif
+}
+
#else
static inline void tick_nohz_switch_to_nohz(void) { }
#endif /* NO_HZ */
/*
+ * Called from irq_enter to notify about the possible interruption of idle()
+ */
+void tick_check_idle(int cpu)
+{
+ tick_check_oneshot_broadcast(cpu);
+#ifdef CONFIG_NO_HZ
+ tick_nohz_stop_idle(cpu);
+ tick_nohz_update_jiffies();
+ tick_nohz_kick_tick(cpu);
+#endif
+}
+
+/*
* High resolution timer specific code
*/
#ifdef CONFIG_HIGH_RES_TIMERS
/*
- * We rearm the timer until we get disabled by the idle code
+ * 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();
int cpu = smp_processor_id();
* this duty, then the jiffies update is still serialized by
* xtime_lock.
*/
- if (unlikely(tick_do_timer_cpu == -1))
+ if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE))
tick_do_timer_cpu = cpu;
#endif
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;
{
struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
ktime_t now = ktime_get();
+ u64 offset;
/*
* 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();
+ /* Get the next period (per cpu) */
+ hrtimer_set_expires(&ts->sched_timer, tick_init_jiffy_update());
+ offset = ktime_to_ns(tick_period) >> 1;
+ do_div(offset, num_possible_cpus());
+ offset *= smp_processor_id();
+ hrtimer_add_expires_ns(&ts->sched_timer, offset);
for (;;) {
hrtimer_forward(&ts->sched_timer, now, tick_period);
- hrtimer_start(&ts->sched_timer, ts->sched_timer.expires,
- HRTIMER_MODE_ABS);
+ hrtimer_start_expires(&ts->sched_timer, HRTIMER_MODE_ABS);
/* Check, if the timer was already in the past */
if (hrtimer_active(&ts->sched_timer))
break;
ts->nohz_mode = NOHZ_MODE_HIGHRES;
#endif
}
+#endif /* HIGH_RES_TIMERS */
+#if defined CONFIG_NO_HZ || defined CONFIG_HIGH_RES_TIMERS
void tick_cancel_sched_timer(int cpu)
{
struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
+# ifdef CONFIG_HIGH_RES_TIMERS
if (ts->sched_timer.base)
hrtimer_cancel(&ts->sched_timer);
- ts->tick_stopped = 0;
+# endif
+
ts->nohz_mode = NOHZ_MODE_INACTIVE;
}
-#endif /* HIGH_RES_TIMERS */
+#endif
/**
* Async notification about clocksource changes
if (ts->nohz_mode != NOHZ_MODE_INACTIVE)
return 0;
- if (!timekeeping_is_continuous() || !tick_is_oneshot_available())
+ if (!timekeeping_valid_for_hres() || !tick_is_oneshot_available())
return 0;
if (!allow_nohz)
git://ftp.safe.ca / safe / jmp / linux-2.6 / blobdiff