linux-kernel - Re: [PATCH 2/3 v2] futex: avoid double wake up in futex

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Message-ID: <alpine.DEB.2.11.1504161248410.3845@nanos>
Date:	Thu, 16 Apr 2015 12:49:59 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Peter Zijlstra <peterz@...radead.org>
cc:	Davidlohr Bueso <dave@...olabs.net>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
	Darren Hart <darren@...art.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	fredrik.markstrom@...driver.com,
	Manfred Spraul <manfred@...orfullife.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>
Subject: Re: [PATCH 2/3 v2] futex: avoid double wake up in futex_wake() on
 -RT

On Thu, 16 Apr 2015, Peter Zijlstra wrote:

> On Thu, Apr 16, 2015 at 11:19:41AM +0200, Thomas Gleixner wrote:
> > So any code which does not handle a spurious wakeup is broken
> > independent of the futex changes. So really nothing to worry about.
> 
> Back when we did this:
> 
>  http://lkml.iu.edu/hypermail/linux/kernel/1109.1/01941.html
>  http://lkml.iu.edu/hypermail/linux/kernel/1109.1/01943.html
> 
> Things came apart -- notably sysvsems.
> 
> And yes its true that anything not dealing with spuriuos wakups is
> borken, but there's still quite a lot of borken out there, although I
> think we fixed all the really common ones.
> 
> But if we decide we want to go do this, I'd propose we reintroduce this
> delayed wake list thing again.

Indeed. Forgot about that completely.

Thanks,

	tglx
 
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