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sched_clock: record TSC after gtod

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To read the gtod we need to grab the xtime lock for read. Reading the gtod
before the TSC can cause a bigger gab if the xtime lock is contended.

This patch simply reverses the order to read the TSC after the gtod.
The locking in the reading of the gtod handles any barriers one might
think is needed.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Cc: Steven Rostedt <srostedt@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: john stultz <johnstul@us.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Steven Rostedt 2008-07-09 00:15:32 -04:00 committed by Ingo Molnar
parent c0c87734f1
commit a83bc47c33
1 changed files with 1 additions and 1 deletions
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2
kernel/sched_clock.c
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@ -237,8 +237,8 @@ void sched_clock_tick(void)
WARN_ON_ONCE(!irqs_disabled());
now = sched_clock();
now_gtod = ktime_to_ns(ktime_get());
now = sched_clock();
__raw_spin_lock(&scd->lock);
__update_sched_clock(scd, now, NULL);