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Subject: Re: futex: priority wakeup miss ordering
From: Daniel Walker <dwalker@mvista.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Pierre Peiffer <peifferp@gmail.com>, LKML <linux-kernel@vger.kernel.org>
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Date: Thu, 08 May 2008 09:28:17 -0700
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On Thu, 2008-05-08 at 12:06 +0200, Thomas Gleixner wrote:

> IIRC this has been discussed before. The priority ordering of the
> plain mutex waiters is an optimization without guarantees of
> correctness across a priority change. It's simply not worth the
> additional complexity and overhead for that corner case.

I've gotten a number of complains about this .. I think it's assumed
that this feature was implementing posix priority queuing for the
standard futex, but it can't be if there are any miss ordered wakeups.

Daniel