Messages in this thread Patch in this message | | | Date | Sun, 13 Nov 2011 18:06:05 +0200 | From | Gleb Natapov <> | Subject | Re: [PATCH] perf: do not set task_ctx pointer in cpuctx if there is no events in the context |
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On Mon, Nov 07, 2011 at 02:00:11PM +0100, Peter Zijlstra wrote: > On Thu, 2011-11-03 at 09:41 +0200, Gleb Natapov wrote: > > Ingo, Peter can you look into this please. > > queued it and the jump_label thing. I see jump_label thing in tip/perf/core but not this one yet. This is good because this one needs amendment :) See below.
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Do not set task_ctx pointer during sched_in if there is no events associated with the context. Otherwise if during task execution total number of events in the system will become zero perf_event_context_sched_out() will not be called and cpuctx->task_ctx will be left with a stale value. Also perf_event_sched_in() shouldn't try to schedule task events in this case otherwise cpuctx->task_ctx->is_active will not be cleared during sched_out and will become incorrect.
Signed-off-by: Gleb Natapov <gleb@redhat.com> diff --git a/kernel/events/core.c b/kernel/events/core.c index d1a1bee..7210657 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -2171,9 +2171,10 @@ static void perf_event_context_sched_in(struct perf_event_context *ctx, */ cpu_ctx_sched_out(cpuctx, EVENT_FLEXIBLE); - perf_event_sched_in(cpuctx, ctx, task); + if (ctx->nr_events) + cpuctx->task_ctx = ctx; - cpuctx->task_ctx = ctx; + perf_event_sched_in(cpuctx, cpuctx->task_ctx, task); perf_pmu_enable(ctx->pmu); perf_ctx_unlock(cpuctx, ctx); -- Gleb.
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