From: Peter Zijlstra <a.p.zijlstra@chello.nl>
Date: Mon, 1 Sep 2008 14:44:23 +0000 (+0200)
Subject: sched_clock: fix NOHZ interaction
X-Git-Tag: v2.6.27-rc6~32^2~1
X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=56c7426b3951e4f35a71d695f1c982989399d6fd;p=linux-2.6

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>
---

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 7a46bde78c..a87b046856 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;
 }