Re: [PATCH 2/5] perf: Destroy event's children on task exit

From: Peter Zijlstra
Date: Fri Jul 11 2014 - 09:23:18 EST

On Fri, Jul 11, 2014 at 01:56:19PM +0200, Jiri Olsa wrote:
> From: Jiri Olsa <jolsa@xxxxxxxxxx>
> When task exits we close:
> 1) all events that are installed in task
> 2) all events owned by task (via file descriptor)
> But we don't close children events of 2) events. Those children
> events stay until the child task exits and are useless with the
> parent being gone, because we have no way to get to values any
> more.
> Plus if the event stays installed in task even with the owner task
> gone, it runs the perf callback any time the task forks, for no
> real reason.
> Closing all children events events when the owner task of the
> parent event is closed.

So I _think_ the reason we didn't do this is because this is potentially
very expensive and keeping them around isn't too much bother, they'll
die eventually.

But I can't really remember. Ingo any recollections / opinions?
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