From: Peter Zijlstra <peterz@infradead.org>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: Possible bug with mutex adaptative spinning
Date: Fri, 16 Apr 2010 23:27:31 +0200 [thread overview]
Message-ID: <1271453251.1674.485.camel@laptop> (raw)
In-Reply-To: <1271213767.13059.137.camel@pasglop>
On Wed, 2010-04-14 at 12:56 +1000, Benjamin Herrenschmidt wrote:
> On Wed, 2010-04-14 at 12:35 +1000, Benjamin Herrenschmidt wrote:
> > Hi Peter !
> >
> > I -may- have found a bug with mutex adaptative spinning. We hit it when
> > torture testing CPU unplug.
>
> .../...
>
> In fact, I wonder if there's another potential problem:
>
> If the owner is actually running, it may do so for a very long time. It
> looks to me that everybody trying to take the mutex will thus spin and
> never get out of the spin loop until the owner stops running.
The inner-most spin loop breaks out on need_resched():
if (task_thread_info(rq->curr) != owner || need_resched())
return 0;
next prev parent reply other threads:[~2010-04-16 21:27 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-04-14 2:35 Possible bug with mutex adaptative spinning Benjamin Herrenschmidt
2010-04-14 2:56 ` Benjamin Herrenschmidt
2010-04-16 21:27 ` Peter Zijlstra [this message]
2010-04-16 22:01 ` Benjamin Herrenschmidt
2010-04-16 21:26 ` Peter Zijlstra
2010-04-16 22:00 ` Benjamin Herrenschmidt
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