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From: Thomas Gleixner <tglx@linutronix.de>
To: Siddhesh Poyarekar <siddhesh.poyarekar@gmail.com>
Cc: Darren Hart <dvhart@linux.intel.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Ingo Molnar <mingo@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH] [RESEND 2] Take over futex of dead task only if FUTEX_WAITERS is not set
Date: Wed, 24 Oct 2012 20:08:18 +0200 (CEST)	[thread overview]
Message-ID: <alpine.LFD.2.02.1210242006450.2756@ionos> (raw)
In-Reply-To: <CAAHN_R0jTey+4TOXfKh96aApOPUXQq6wwobejmhFeRuTV2VJKA@mail.gmail.com>

On Wed, 24 Oct 2012, Siddhesh Poyarekar wrote:

> > Now there is a different solution to that problem. Do not look at the
> > user space value at all and enforce a lookup of possibly available
> > pi_state. If pi_state can be found, then the new incoming locker T3
> > blocks on that pi_state and legitimately races with T2 to acquire the
> > rt_mutex and the pi_state and therefor the proper ownership of the
> > user space futex.
> 
> That works. Thanks for the detailed explanation too.

Thanks for the reproducer and finding the trouble spot in the first
place!

I'll queue that if Darren has no objections and mark it for stable as
well.

Thanks,

	tglx

  reply	other threads:[~2012-10-24 18:08 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-10-11 14:52 [PATCH] Take over futex of dead task only if FUTEX_WAITERS is not set Siddhesh Poyarekar
2012-10-17  7:15 ` [PATCH RESEND] " Siddhesh Poyarekar
2012-10-22  3:20   ` [PATCH] [RESEND 2] " Siddhesh Poyarekar
2012-10-23 14:04     ` Darren Hart
2012-10-23 20:29       ` Thomas Gleixner
2012-10-24 12:48         ` Siddhesh Poyarekar
2012-10-24 18:08           ` Thomas Gleixner [this message]
2012-10-25  4:36             ` Darren Hart
2012-10-25  4:44               ` Siddhesh Poyarekar
2012-10-25  4:33         ` Darren Hart
2012-10-25  8:14           ` Thomas Gleixner
2012-10-25  8:18             ` Darren Hart
2012-11-01 21:35         ` [tip:core/urgent] futex: Handle futex_pi OWNER_DIED take over correctly tip-bot for Thomas Gleixner

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