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Date: Mon, 14 Apr 2008 09:18:00 +0200
From: Ingo Molnar <mingo@elte.hu>
To: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>, Miles Lane <miles.lane@gmail.com>,
       LKML <linux-kernel@vger.kernel.org>, Gautham Shenoy <ego@in.ibm.com>,
       "Rafael J. Wysocki" <rjw@sisk.pl>, Steven Rostedt <rostedt@goodmis.org>
Subject: Re: 2.6.25-rc9 -- INFO: possible circular locking dependency
	detected
Message-ID: <20080414071800.GE16163@elte.hu>
References: <a44ae5cd0804132004v2bef54fek6e9634f8bce087ab@mail.gmail.com> <1208156045.7427.16.camel@twins> <20080414070234.GA7482@osiris.boeblingen.de.ibm.com>
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* Heiko Carstens <heiko.carstens@de.ibm.com> wrote:

> On Mon, Apr 14, 2008 at 08:54:05AM +0200, Peter Zijlstra wrote:
> > Fun,
> > 
> > I will need to sort out this code before I can say anything about that,
> > perhaps Gautham and or Rafael have ideas before I can come up with
> > something.. ?
> 
> Why not simply removing the get/put_online_cpus() pair in 
> sched_getaffinity? It's superfluous since we have already a 
> read_lock/read_unlock pair there which does disable/enable cpu hotplug 
> anyway.

we dont want to insert such silent "preempt off == hotplug disable" 
assumptions - which assumption breaks when the tasklist_lock becomes 
preemptible (such as in -rt).

	Ingo