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perf_event: Cleanup for cpu_clock_perf_event_update()

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Using atomic64_xchg() instead of atomic64_read() and
atomic64_set().

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Reviewed-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <4B1F19DC.90204@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Xiao Guangrong 2009-12-09 11:30:36 +08:00 committed by Ingo Molnar
parent b93f7978ad
commit ec89a06fd4
1 changed files with 1 additions and 2 deletions
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3
kernel/perf_event.c
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@ -4079,8 +4079,7 @@ static void cpu_clock_perf_event_update(struct perf_event *event)
u64 now;
now = cpu_clock(cpu);
prev = atomic64_read(&event->hw.prev_count);
atomic64_set(&event->hw.prev_count, now);
prev = atomic64_xchg(&event->hw.prev_count, now);
atomic64_add(now - prev, &event->count);
}