From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Peter Zijlstra <peterz@infradead.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: Wed, 14 Apr 2010 12:56:07 +1000 [thread overview]
Message-ID: <1271213767.13059.137.camel@pasglop> (raw)
In-Reply-To: <1271212509.13059.135.camel@pasglop>
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.
That sounds very wrong to me :-)
Shouldn't you at least remove the test for !owner when testing
need_resched() in __mutex_lock_common() ?
Cheers,
Ben.
next prev parent reply other threads:[~2010-04-14 2:57 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 [this message]
2010-04-16 21:27 ` Peter Zijlstra
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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