From e4e22f2acebe19f94bd6a8ef8f9a34ed8952a1f0 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Tue, 31 May 2011 12:26:55 +0200 Subject: [PATCH] sched: Fix cross-cpu clock sync on remote wakeups Markus reported that commit a464723963d ("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 Signed-off-by: Peter Zijlstra Link: http://lkml.kernel.org/r/1306835745.2353.3.camel@twins Signed-off-by: Ingo Molnar --- kernel/sched.c | 1 + 1 file changed, 1 insertion(+) diff --git a/kernel/sched.c b/kernel/sched.c index cbb3a0eee58eb..49cc70b152cf0 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; } -- 2.39.5