sched_clock: fix NOHZ interaction

If HLT stops the TSC, we'll fail to account idle time, thereby inflating the
actual process times. Fix this by re-calibrating the clock against GTOD when
leaving nohz mode.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Tested-by: Avi Kivity <avi@qumranet.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 3 insertions, 0 deletions

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 7a46bde78c66..a87b0468568b 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -162,6 +162,8 @@ void tick_nohz_stop_idle(int cpu)
                 ts->idle_lastupdate = now;
                 ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta);
                 ts->idle_active = 0;
+
+                sched_clock_idle_wakeup_event(0);
         }
 }
 
@@ -177,6 +179,7 @@ static ktime_t tick_nohz_start_idle(struct tick_sched *ts)
         }
         ts->idle_entrytime = now;
         ts->idle_active = 1;
+        sched_clock_idle_sleep_event();
         return now;
 }