Commit-ID: 527e26af3741a2168986d8b82653ffe173891324 Gitweb: http://git.kernel.org/tip/527e26af3741a2168986d8b82653ffe173891324 Author: Robert Richter <robert.richter@xxxxxxx> AuthorDate: Wed, 29 Apr 2009 12:47:02 +0200 Committer: Ingo Molnar <mingo@xxxxxxx> CommitDate: Wed, 29 Apr 2009 14:51:02 +0200 perf_counter, x86: protect per-cpu variables with compile barriers only Per-cpu variables needn't to be protected with cpu barriers (smp_wmb()). Protection is only needed for preemption on the same cpu (rescheduling or the nmi handler). This can be done using a compiler barrier only. [ Impact: micro-optimization ] Signed-off-by: Robert Richter <robert.richter@xxxxxxx> Cc: Paul Mackerras <paulus@xxxxxxxxx> Acked-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> LKML-Reference: <1241002046-8832-6-git-send-email-robert.richter@xxxxxxx> Signed-off-by: Ingo Molnar <mingo@xxxxxxx> --- arch/x86/kernel/cpu/perf_counter.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/cpu/perf_counter.c b/arch/x86/kernel/cpu/perf_counter.c index 75a0903..ad663d5 100644 --- a/arch/x86/kernel/cpu/perf_counter.c +++ b/arch/x86/kernel/cpu/perf_counter.c @@ -673,7 +673,7 @@ try_generic: /* * Make it visible before enabling the hw: */ - smp_wmb(); + barrier(); __hw_perf_counter_set_period(counter, hwc, idx); __pmc_generic_enable(counter, hwc, idx); @@ -745,7 +745,7 @@ static void pmc_generic_disable(struct perf_counter *counter) * Make sure the cleared pointer becomes visible before we * (potentially) free the counter: */ - smp_wmb(); + barrier(); /* * Drain the remaining delta count out of a counter -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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