linux-kernel - Re: futex: priority wakeup miss ordering

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Date:	Thu, 08 May 2008 09:28:17 -0700
From:	Daniel Walker <dwalker@...sta.com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Pierre Peiffer <peifferp@...il.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: futex: priority wakeup miss ordering


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

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