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

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Message-ID: <87lh7hhmnn.fsf@ashishki-desk.ger.corp.intel.com>
Date:	Fri, 22 Jan 2016 13:35:40 +0200
From:	Alexander Shishkin <alexander.shishkin@...ux.intel.com>
To:	Peter Zijlstra <peterz@...radead.org>
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

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

> So I think there's a number of problems still :-(

Also, it does indeed race with
__perf_event_exit_task()/sync_child_event(), but that one I'd fix by
simply wrapping the sync_child_event()/free_event() in

mutex_lock(&parent_event->child_mutex);
if (!is_orphan_event(parent_event)) {
   sync_child_event(child_event);
   free_event(child_event);
}
mutex_unlock(&parent_event->child_event);

At some later point in time the code there could use a bit of
reshuffling, I guess.

Regards,
--
Alex