lkml.org 
[lkml]   [2009]   [Mar]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[PATCH 05/11] perf_counter: add comment to barrier
We need to ensure the enabled=0 write happens before we start disabling
the actual counters, so that a pcm_amd_enable() will not enable one underneath
us.

I think the race is impossible anyway, we always balance the ops within any
one context and perform enable() with IRQs disabled.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
arch/x86/kernel/cpu/perf_counter.c | 4 ++++
1 file changed, 4 insertions(+)
Index: linux-2.6/arch/x86/kernel/cpu/perf_counter.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/cpu/perf_counter.c
+++ linux-2.6/arch/x86/kernel/cpu/perf_counter.c
@@ -247,6 +247,10 @@ static u64 pmc_amd_save_disable_all(void

enabled = cpuc->enabled;
cpuc->enabled = 0;
+ /*
+ * ensure we write the disable before we start disabling the
+ * counters proper, so that pcm_amd_enable() does the right thing.
+ */
barrier();

for (idx = 0; idx < nr_counters_generic; idx++) {
--



\
 
 \ /
  Last update: 2009-03-13 12:27    [from the cache]
©2003-2011 Jasper Spaans