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

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Message-Id: <20080508012503.0d023cdc.akpm@linux-foundation.org>
Date:	Thu, 8 May 2008 01:25:03 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Daniel Walker <dwalker@...sta.com>
Cc:	linux-kernel@...r.kernel.org, Pierre Peiffer <peifferp@...il.com>
Subject: Re: futex: priority wakeup miss ordering

On Wed, 07 May 2008 14:22:58 -0700 Daniel Walker <dwalker@...sta.com> wrote:

> 
> 
> from commit ec92d08292d3e9b0823eba138a4564d2d39f25c7
> 
> The wakeup ordering should be in priority order. However if the priority
> of a task is modified while it's waiting on the futex you will get an
> out of order wakeup.
> 
> If you use a priority inheriting mutex this is correct. It's because the
> rtmutex hooks into sched_setscheduler to catch any priority changes,
> then re-queues with the new priority.. But the futex doesn't have this
> hook.
> 
> Was this intentionally left out of this priority wake up patch? I
> thought I would let you know in case you had a specific reason for not
> handling this.. 
> 

Pierre is no longer @bull.net.
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