From f9fccdb9efef60dbcf84d493514b475c41aa866f Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Fri, 21 Apr 2017 12:43:59 +0200 Subject: [PATCH] cpuidle: Fix idle time tracking MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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: e93e59ce5b85 ("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: Ville Syrjälä Tested-by: Ville Syrjälä Signed-off-by: Peter Zijlstra (Intel) Cc: Daniel Lezcano Cc: Linus Torvalds Cc: Mike Galbraith Cc: Peter Zijlstra Cc: Rafael J . Wysocki Cc: Thomas Gleixner Cc: linux-kernel@vger.kernel.org Fixes: e93e59ce5b85 ("cpuidle: Replace ktime_get() with local_clock()") Signed-off-by: Ingo Molnar --- drivers/cpuidle/cpuidle.c | 1 + kernel/sched/clock.c | 11 +++++++++-- 2 files changed, 10 insertions(+), 2 deletions(-) diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c index 2706be7ed334..60bb64f4329d 100644 --- a/drivers/cpuidle/cpuidle.c +++ b/drivers/cpuidle/cpuidle.c @@ -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); diff --git a/kernel/sched/clock.c b/kernel/sched/clock.c index c30c05f05d6f..d4c2f89fac92 100644 --- a/kernel/sched/clock.c +++ b/kernel/sched/clock.c @@ -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); -- 2.20.1