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:

  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 <ville.syrjala@linux.intel.com>
Tested-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Peter 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: e93e59ce5b85 ("cpuidle: Replace ktime_get() with local_clock()")
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
index 2706be7ed3340fe41ad174d75dc27a9e010e4412..60bb64f4329da292f3eeac6846f4bf6fb179cbb9 100644 (file)
--- 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 c30c05f05d6fff56001c6cb0ff9c804c45edb735..d4c2f89fac922b39bc697e7699f9c82468d76bdd 100644 (file)
--- 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);