Commit a83bc47c authored Jul 09, 2008 by Steven Rostedt Committed by Ingo Molnar Jul 11, 2008

sched_clock: record TSC after gtod



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>

parent c0c87734

kernel/sched_clock.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -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);

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