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Subject: Re: Q: perf_event && event->owner
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>, Alan Stern <stern@rowland.harvard.edu>,
        Arnaldo Carvalho de Melo <acme@redhat.com>,
        Ingo Molnar <mingo@elte.hu>, Paul Mackerras <paulus@samba.org>,
        Prasad <prasad@linux.vnet.ibm.com>, Roland McGrath <roland@redhat.com>,
        linux-kernel@vger.kernel.org
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Date: Mon, 08 Nov 2010 21:41:12 +0100
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On Mon, 2010-11-08 at 21:11 +0100, Frederic Weisbecker wrote:
> Perhaps the real owner should be the task on which we attach our
> breakpoint.

No the point of event->owner is to point to the task that creates the
event, not the task we possibly attach it to (that should be reachable
through event->ctx->task).

As to removing event->owner as Oleg suggests, its a published ABI and
there might be people using it.

The use-case is a monitor thread wanting to stop all monitoring it
initiated, for example because its wants to synchronize various counters
attached to different tasks etc..