linux-kernel - Re: [RFC PATCH 1/1] perf/core: Wake up parent event if inherited event has no ring buffer

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Message-ID: <b0de5ea6-4100-15ed-bbf8-8578a0fa5b6d@arm.com>
Date:   Wed, 26 Jan 2022 16:15:30 +0000
From:   James Clark <james.clark@....com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     mingo@...hat.com, acme@...nel.org, mark.rutland@....com,
        alexander.shishkin@...ux.intel.com, jolsa@...hat.com,
        namhyung@...nel.org, linux-perf-users@...r.kernel.org,
        leo.yan@...aro.com, Suzuki.Poulose@....com,
        Ruben Ayrapetyan <Ruben.Ayrapetyan@....com>,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 1/1] perf/core: Wake up parent event if inherited
 event has no ring buffer



On 25/01/2022 19:12, Peter Zijlstra wrote:
> On Mon, Jan 24, 2022 at 02:58:18PM +0000, James Clark wrote:
> 
>>> Would this be the better patch?
>>
>> Yes I tested this and it also works.
> 
> Excellent!
> 
>> There is one other suspicious access
>> of ->rb followed by if(rb) here in perf_poll(), but maybe it works out ok?
>>
>> 	mutex_lock(&event->mmap_mutex);
>> 	rb = event->rb;
>> 	if (rb)
>> 		events = atomic_xchg(&rb->poll, 0);
>>
> 
> That case must be good since it is the event from a file. Those cannot
> be clones.
> 
>> We also have a Perf self test that covers this failure for Arm SPE now, I'm not
>> sure if I should post that separately or with your new version of this fix?
> 
> They'd be routed through separate trees anyway, Arnaldo takes the
> userspace stuff.
> 

Ok we will post that one separately then. What are the next steps for this one?
Will you just put your version directly in your tree, or should I resubmit it with a
new commit message?