linux-kernel - Re: [PATCH] futex: Fix ZERO

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Message-ID: <a36005b50912240915u48f326efh1d2c49980e79609c@mail.gmail.com>
Date:	Thu, 24 Dec 2009 09:15:47 -0800
From:	Ulrich Drepper <drepper@...il.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Hugh Dickins <hugh.dickins@...cali.co.uk>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Nick Piggin <npiggin@...e.de>, Ingo Molnar <mingo@...e.hu>,
	LKML <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Darren Hart <dvhltc@...ibm.com>
Subject: Re: [PATCH] futex: Fix ZERO_PAGE cause infinite loop

On Thu, Dec 24, 2009 at 01:39, Peter Zijlstra <peterz@...radead.org> wrote:
> What I mean is, all (?) futex ops assume userspace actually wrote
> something to the address in question to begin with, therefore it can
> never be the zero page.

In practice today this is likely always the case.  But it doesn't have
to be like that.  In theory a zero-initialized futex is a reasonable
object on which to wait.  You should not preclude this from happening
just because it's not done like this today.
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