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SubjectRe: [PATCH] perf cgroups: Fix perf_cgroup_switch schedule in warning
From
Cool. Thanks.

On Tue, Oct 2, 2012 at 3:46 PM, Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:
> On Tue, 2012-10-02 at 15:34 +0200, Stephane Eranian wrote:
>> And adding a comment in cgroup_switch()
>>
>> + /* ensure we process each cpuctx only once */
>> + if (cpuctx->active_pmu != pmu)
>> + continue;
>>
> ---
> Subject: perf: Fix perf_cgroup_switch for sw-events
> From: Peter Zijlstra <a.p.zijlstra@chello.nl>
> Date: Tue Oct 02 15:41:23 CEST 2012
>
> Jiri reported that he could trigger the WARN_ON_ONCE() in
> perf_cgroup_switch() using sw-events. This is because sw-events share
> a cpuctx with multiple PMUs.
>
> Use the ->unique_pmu pointer to limit the pmu iteration to unique
> cpuctx instances.
>
> Reported-and-Tested-by: Jiri Olsa <jolsa@redhat.com>
> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
> ---
> kernel/events/core.c | 9 ++++++---
> 1 file changed, 6 insertions(+), 3 deletions(-)
>
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -372,6 +372,8 @@ void perf_cgroup_switch(struct task_stru
>
> list_for_each_entry_rcu(pmu, &pmus, entry) {
> cpuctx = this_cpu_ptr(pmu->pmu_cpu_context);
> + if (cpuctx->unique_pmu != pmu)
> + continue; /* ensure we process each cpuctx once */
>
> /*
> * perf_cgroup_events says at least one
> @@ -395,9 +397,10 @@ void perf_cgroup_switch(struct task_stru
>
> if (mode & PERF_CGROUP_SWIN) {
> WARN_ON_ONCE(cpuctx->cgrp);
> - /* set cgrp before ctxsw in to
> - * allow event_filter_match() to not
> - * have to pass task around
> + /*
> + * set cgrp before ctxsw in to allow
> + * event_filter_match() to not have to pass
> + * task around
> */
> cpuctx->cgrp = perf_cgroup_from_task(task);
> cpu_ctx_sched_in(cpuctx, EVENT_ALL, task);
>


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