From a83bc47c33ab182f1e48977fd5a04024d713c75e Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Wed, 9 Jul 2008 00:15:32 -0400 Subject: [PATCH] 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 Cc: Steven Rostedt Cc: Peter Zijlstra Cc: Andrew Morton Cc: john stultz Signed-off-by: Ingo Molnar --- kernel/sched_clock.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/sched_clock.c b/kernel/sched_clock.c index ee7cce5..28ff6bf 100644 --- a/kernel/sched_clock.c +++ b/kernel/sched_clock.c @@ -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); -- 2.7.4