linux-kernel - Re: [PATCH] [RESEND 2] Take over futex of dead task only if FUTEX

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Message-ID: <5088F5D0.7010604@linux.intel.com>
Date:	Thu, 25 Oct 2012 01:18:24 -0700
From:	Darren Hart <dvhart@...ux.intel.com>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	Siddhesh Poyarekar <siddhesh.poyarekar@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH] [RESEND 2] Take over futex of dead task only if FUTEX_WAITERS
 is not set



On 10/25/2012 01:14 AM, Thomas Gleixner wrote:
> On Wed, 24 Oct 2012, Darren Hart wrote:
>> On 10/23/2012 01:29 PM, Thomas Gleixner wrote:

> Nah. I'm just too paranoid to apply any futex patch w/o understanding
> the root cause of it.  Darn, if I only could remember how that stale
> waiters bit issue got inflicted ....

Stale waiters happens in userspace for non-pi mutexes and there we make
one extra FUTEX_WAKE syscall just in case. The futex value policy is much
more rigid with PI obviously, so I wasn't aware this could happen there.

-- 
Darren Hart
Intel Open Source Technology Center
Yocto Project - Technical Lead - Linux Kernel
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