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authorPeter Zijlstra <a.p.zijlstra@chello.nl>2011-05-31 12:26:55 +0200
committerIngo Molnar <mingo@elte.hu>2011-05-31 14:19:56 +0200
commitf01114cb59d670e9b4f2c335930dd57db96e9360 (patch)
tree98e2c76fd78e1e6762c92423a3e6f867a027ca3c /kernel/sched.c
parent1e1b6c511d1b23cb7c3b619d82fc7bd9f620565d (diff)
sched: Fix cross-cpu clock sync on remote wakeups
Markus reported that commit 317f394160e ("sched: Move the second half of ttwu() to the remote cpu") caused some accounting funnies on his AMD Phenom II X4, such as weird 'top' results. It turns out that this is due to non-synced TSC and the queued remote wakeups stopped coupeling the two relevant cpu clocks, which leads to wakeups seeing time jumps, which in turn lead to skewed runtime stats. Add an explicit call to sched_clock_cpu() to couple the per-cpu clocks to restore the normal flow of time. Reported-and-tested-by: Markus Trippelsdorf <markus@trippelsdorf.de> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/1306835745.2353.3.camel@twins Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/sched.c')
-rw-r--r--kernel/sched.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/kernel/sched.c b/kernel/sched.c
index cbb3a0eee58..49cc70b152c 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -2600,6 +2600,7 @@ static void ttwu_queue(struct task_struct *p, int cpu)
#if defined(CONFIG_SMP)
if (sched_feat(TTWU_QUEUE) && cpu != smp_processor_id()) {
+ sched_clock_cpu(cpu); /* sync clocks x-cpu */
ttwu_queue_remote(p, cpu);
return;
}