linux-kernel - Re: [PATCH v2 1/4] perf: Allow using AUX data in perf samples

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Date:   Fri, 25 Oct 2019 15:52:33 +0300
From:   Alexander Shishkin <alexander.shishkin@...ux.intel.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Arnaldo Carvalho de Melo <acme@...hat.com>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        jolsa@...hat.com, adrian.hunter@...el.com,
        mathieu.poirier@...aro.org, mark.rutland@....com,
        alexander.shishkin@...ux.intel.com
Subject: Re: [PATCH v2 1/4] perf: Allow using AUX data in perf samples

Peter Zijlstra <peterz@...radead.org> writes:

> On Tue, Oct 22, 2019 at 12:58:09PM +0300, Alexander Shishkin wrote:
>> @@ -11213,6 +11367,9 @@ SYSCALL_DEFINE5(perf_event_open,
>>  	if (event->attr.aux_output && !perf_get_aux_event(event, group_leader))
>>  		goto err_locked;
>>  
>> +	if (event->attr.aux_sample_size && !perf_get_aux_event(event, group_leader))
>> +		goto err_locked;
>> +
>
> Either aux_sample_size and aux_output are mutually exclusive, or you're
> leaking a refcount on group_leader. The first wants a check, the second
> wants error path fixes.

Now you mention it, it should be possible to have both. Whether that's
useful is another question. But we only need one reference either way.

Thanks,
--
Alex