From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@elte.hu>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Tony Breeds <tonyb@au1.ibm.com>,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH/RFC] mutex: Fix optimistic spinning vs. BKL
Date: Wed, 28 Apr 2010 14:39:34 +1000 [thread overview]
Message-ID: <1272429574.24542.84.camel@pasglop> (raw)
In-Reply-To: <1272429513.24542.83.camel@pasglop>
On Wed, 2010-04-28 at 14:38 +1000, Benjamin Herrenschmidt wrote:
> Currently, we can hit a nasty case with optimistic spinning on mutexes:
>
> CPU A tries to take a mutex, while holding the BKL
>
> CPU B tried to take the BLK while holding the mutex
>
> This looks like a AB-BA scenario but in practice, is allowed and happens
> due to the auto-release-on-schedule nature of the BKL.
.../...
BTW. The patch is only compile-tested so far :-) It's going to be
hammered with the test case that triggered the original bug hopefully
tonight.
Cheers,
Ben.
next prev parent reply other threads:[~2010-04-28 4:46 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-04-28 4:38 [PATCH/RFC] mutex: Fix optimistic spinning vs. BKL Benjamin Herrenschmidt
2010-04-28 4:39 ` Benjamin Herrenschmidt [this message]
2010-04-28 12:06 ` Arnd Bergmann
2010-04-28 22:35 ` Benjamin Herrenschmidt
2010-05-07 4:20 ` Tony Breeds
2010-05-07 5:30 ` Frederic Weisbecker
2010-05-07 6:01 ` Benjamin Herrenschmidt
2010-05-07 21:29 ` Frederic Weisbecker
2010-05-07 22:27 ` Benjamin Herrenschmidt
2010-05-10 7:55 ` Peter Zijlstra
2010-05-11 18:06 ` Linus Torvalds
2010-05-11 18:19 ` Peter Zijlstra
2010-05-11 21:13 ` Benjamin Herrenschmidt
2010-05-07 6:16 ` Mike Galbraith
2010-05-11 15:43 ` [tip:core/locking] " tip-bot for Tony Breeds
2010-05-11 23:05 ` Tony Breeds
2010-05-18 16:08 ` Ingo Molnar
2010-05-18 16:26 ` Linus Torvalds
2010-05-19 5:46 ` Tony Breeds
2010-05-19 7:56 ` [tip:core/urgent] " tip-bot for Tony Breeds
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