Commit-ID: 1b1646b16f983a880163afb9efd296de01c7d854 Gitweb: http://git.kernel.org/tip/1b1646b16f983a880163afb9efd296de01c7d854 Author: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> AuthorDate: Fri, 13 Mar 2009 12:21:30 +0100 Commit: Ingo Molnar <mingo@xxxxxxx> CommitDate: Fri, 13 Mar 2009 13:59:08 +0100 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@xxxxxxxxx> LKML-Reference: <20090313112301.384074618@xxxxxxxxx> Signed-off-by: Ingo Molnar <mingo@xxxxxxx> --- arch/x86/kernel/cpu/perf_counter.c | 4 ++++ 1 files changed, 4 insertions(+), 0 deletions(-) diff --git a/arch/x86/kernel/cpu/perf_counter.c b/arch/x86/kernel/cpu/perf_counter.c index 1cedc34..a2e3b76 100644 --- a/arch/x86/kernel/cpu/perf_counter.c +++ b/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++) { -- 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