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Commit f9fccdb9 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

cpuidle: Fix idle time tracking 



Ville reported that on his Core2, which has TSC stop in idle, we would
always report very short idle durations. He tracked this down to
commit:

  e93e59ce ("cpuidle: Replace ktime_get() with local_clock()")

which replaces ktime_get() with local_clock().

Add a sched_clock_idle_wakeup_event() call, which will re-sync the
clock with ktime_get_ns() when TSC is unstable and no-op otherwise.

Reported-by: default avatarVille Syrjälä <ville.syrjala@linux.intel.com>
Tested-by: default avatarVille Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rafael J . Wysocki <rafael.j.wysocki@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Fixes: e93e59ce ("cpuidle: Replace ktime_get() with local_clock()")
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 3067a33d

drivers/cpuidle/cpuidle.c

+1 −0
Original line number Diff line number Diff line
@@ -220,6 +220,7 @@ int cpuidle_enter_state(struct cpuidle_device *dev, struct cpuidle_driver *drv, 
	entered_state = target_state->enter(dev, drv, index);

	start_critical_timings();



	sched_clock_idle_wakeup_event();

	time_end = ns_to_ktime(local_clock());

	trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, dev->cpu);

kernel/sched/clock.c

+9 −2
Original line number Diff line number Diff line
@@ -410,14 +410,21 @@ void sched_clock_idle_sleep_event(void) 
EXPORT_SYMBOL_GPL(sched_clock_idle_sleep_event);



/*

 * We just idled; resync with ktime. (called with irqs disabled):

 * We just idled; resync with ktime.

 */

void sched_clock_idle_wakeup_event(void)

{

	if (timekeeping_suspended)

	unsigned long flags;



	if (sched_clock_stable())

		return;



	if (unlikely(timekeeping_suspended))

		return;



	local_irq_save(flags);

	sched_clock_tick();

	local_irq_restore(flags);

}

EXPORT_SYMBOL_GPL(sched_clock_idle_wakeup_event);