sched: Fix cross-cpu clock sync on remote wakeups
authorPeter Zijlstra <a.p.zijlstra@chello.nl>
Tue, 31 May 2011 10:26:55 +0000 (12:26 +0200)
committerIngo Molnar <mingo@elte.hu>
Tue, 31 May 2011 12:19:56 +0000 (14:19 +0200)
commitf01114cb59d670e9b4f2c335930dd57db96e9360
tree98e2c76fd78e1e6762c92423a3e6f867a027ca3c
parent1e1b6c511d1b23cb7c3b619d82fc7bd9f620565d
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>
kernel/sched.c