From mboxrd@z Thu Jan  1 00:00:00 1970
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: Re: perf: prctl(PR_TASK_PERF_EVENTS_DISABLE) has no effect
Date: Tue, 31 Jul 2012 21:48:52 +0200
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To: Ingo Molnar <mingo@kernel.org>
Cc: Iegorov Oleg <oleg_iegorov@mentor.com>, linux-perf-users@vger.kernel.org, mingo@elte.hu, acme@ghostprotocols.net, =?ISO-8859-1?Q?Fr=E9d=E9ric?= Weisbecker <fweisbec@gmail.com>, Arnaldo Carvalho de Melo <acme@infradead.org>, Thomas Gleixner <tglx@linutronix.de>

On Tue, 2012-07-31 at 09:16 +0200, Ingo Molnar wrote:
> * Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:
> 
> > On Fri, 2012-07-27 at 13:53 +0200, Ingo Molnar wrote:
> > > > Bloating the interface for something that is already well 
> > > > possible is.
> > > 
> > > There's no 'bloat' worth speaking off: a single bit out of 
> > > an already allocated bitmap, plus a single check in an 
> > > already existing loop,
> > 
> > Uhm, no. The existing prctl() loop is over the fd's the task 
> > owns, you want a loop over the fd's that monitor you. This 
> > needs new prctl()s at the very least.
> 
> We could add a new prctl if you think, but I thought to not 
> complicate it and offer it as a simple extension of the 
> semantics to loop over active events. No existing binary's 
> behavior will change.

It muddles up the semantics of the existing prctl()s though.

Ideally we'd simply remove the current ones though, I don't think
anybody actually uses them and as an owner you actually have all the fds
to call ioctl() on.

This would let us get rid of the entire event->owner, event->owner_entry
and task->perf_event_list mess. See perf_event_exit_task() and
perf_release() for why I'd love that crap to go away.