linux-kernel - Re: [PATCH] perf cgroups: Fix perf_cgroup

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Date:	Tue, 2 Oct 2012 14:48:30 +0200
From:	Stephane Eranian <eranian@...gle.com>
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	LKML <linux-kernel@...r.kernel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...e.hu>, Paul Mackerras <paulus@...ba.org>,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: Re: [PATCH] perf cgroups: Fix perf_cgroup_switch schedule in warning

On Tue, Oct 2, 2012 at 2:39 PM, Jiri Olsa <jolsa@...hat.com> wrote:
> On Tue, Oct 02, 2012 at 01:53:01PM +0200, Peter Zijlstra wrote:
>> On Tue, 2012-10-02 at 13:42 +0200, Jiri Olsa wrote:
>> > +++ b/kernel/events/core.c
>> > @@ -394,7 +394,8 @@ void perf_cgroup_switch(struct task_struct *task, int mode)
>> >                         }
>> >
>> >                         if (mode & PERF_CGROUP_SWIN) {
>> > -                               WARN_ON_ONCE(cpuctx->cgrp);
>> > +                               WARN_ON_ONCE(cpuctx->cgrp && !cpuctx->ctx.is_active);
>> > +
>> >                                 /* set cgrp before ctxsw in to
>> >                                  * allow event_filter_match() to not
>> >                                  * have to pass task around
>>
>> OK, like you mentioned this is the result of multiple PMU being able to
>> share a cpuctx, shouldn't we in that case avoid the second loop over the
>> cpuctx as a whole?
>>
Not sure, I understand what active_pmu represents.

>> Would something like the below do? IIRC I introduced that active_pmu for
>> exactly such reasons..
>>
>> ---
>>  kernel/events/core.c | 2 ++
>>  1 file changed, 2 insertions(+)
>>
>> diff --git a/kernel/events/core.c b/kernel/events/core.c
>> index 7b9df35..e98f014 100644
>> --- a/kernel/events/core.c
>> +++ b/kernel/events/core.c
>> @@ -372,6 +372,8 @@ void perf_cgroup_switch(struct task_struct *task, int mode)
>>
>>       list_for_each_entry_rcu(pmu, &pmus, entry) {
>>               cpuctx = this_cpu_ptr(pmu->pmu_cpu_context);
>> +             if (cpuctx->active_pmu != pmu)
>> +                     continue;
>>
>>               /*
>>                * perf_cgroup_events says at least one
>>
>
> this passed my test
>
> jirka
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