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authorSteven Rostedt <rostedt@goodmis.org>2008-07-09 00:15:32 -0400
committerIngo Molnar <mingo@elte.hu>2008-07-11 15:53:27 +0200
commita83bc47c33ab182f1e48977fd5a04024d713c75e (patch)
tree759eb1afc83271ee2815dbd1214635ec7b506b5c /kernel
parentc0c87734f125d2fa8ebc70310f3257fa6209f2b6 (diff)
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>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/sched_clock.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/sched_clock.c b/kernel/sched_clock.c
index ee7cce5029c..28ff6bf5e02 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);