[PATCH 05/29] x86/perfcounters: protect per-cpu variables with compile barriers only

Robert Richter
2009-04-29T10:56:29Z

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.

Signed-off-by: Robert Richter <robert.richter@amd.com>
---
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
--
1.6.1.3