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Message-ID: <20100326172350.GC5188@nowhere>
Date: Fri, 26 Mar 2010 18:23:54 +0100
From: Frederic Weisbecker <fweisbec@...il.com>
To: Mike Galbraith <efault@....de>
Cc: Li Zefan <lizf@...fujitsu.com>,
LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
Peter Zijlstra <peterz@...radead.org>,
Arnaldo Carvalho de Melo <acme@...hat.com>,
Paul Mackerras <paulus@...ba.org>
Subject: Re: [BUG] perf: hard lockup when using perf-sched
On Fri, Mar 26, 2010 at 11:11:33AM +0100, Mike Galbraith wrote:
> On Thu, 2010-03-25 at 10:27 +0100, Mike Galbraith wrote:
> > On Thu, 2010-03-25 at 16:04 +0800, Li Zefan wrote:
> > > Mike Galbraith wrote:
> > > > On Wed, 2010-03-24 at 08:32 +0100, Mike Galbraith wrote:
> > > >
> > > >> I just saw this, hunted down your testcase and tried it here. Looks
> > > >> like perf_output_lock() wedged box.
> > > >
> > > > (turns on frame pointers, and adds noinline)
> > > >
> > >
> > > Thanks! Then who's going to fix this...
> >
> > Well, that kinda depends on whether I figure out how the heck it's all
> > supposed to work before somebody else whacks it or not.
>
> This seems to work, in contrast to everything I tried yesterday. Not
> exactly a thing of beauty, but at least it's an option, so...
>
> perf: fix perf sched record forkbomb deadlock
>
> perf sched record can deadlock a box should the holder of handle->data->lock
> take an interrupt, and then attempt to acquire an rq lock held by a CPU trying
> to acquire the same lock. Disable interrupts.
Aah.
So the scenario is the following inversion?
CPU0 CPU1
sched event with rq->lock held
grab handle->data->lock
spin on handle->data->lock
interrupt
try to grab rq->lock
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