linux-kernel - Re: [PATCH v2] perf: Synchronously cleanup child events

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Date:	Wed, 20 Jan 2016 09:03:20 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc:	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
	vince@...ter.net, eranian@...gle.com,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Jiri Olsa <jolsa@...nel.org>, alexei.starovoitov@...il.com
Subject: Re: [PATCH v2] perf: Synchronously cleanup child events

On Wed, Jan 20, 2016 at 09:04:28AM +0200, Alexander Shishkin wrote:
> Peter Zijlstra <peterz@...radead.org> writes:

> > The most obvious place that generates such magical references would be
> > the bpf arraymap doing perf_event_get() on things. There are a few other
> > places that take temp references (perf_mmap_close), but those are
> > 'short' lived and while ugly will not cause massive grief.
> 
> We won't get to perf_release() before we're done with perf_mmap_close(),
> so that one's not really a problem.

Only for the file we mmap()'ed, the events we've attached through
IOC_SET_OUTPUT will not have a file reference from the mmap().