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Date: Sat, 24 Mar 2012 12:12:12 +0100
From: Richard Weinberger <richard@nod.at>
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To: Anton Vorontsov <anton.vorontsov@linaro.org>
CC: Andrew Morton <akpm@linux-foundation.org>, Oleg Nesterov <oleg@redhat.com>,
        Russell King <linux@arm.linux.org.uk>,
        Mike Frysinger <vapier@gentoo.org>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mundt <lethal@linux-sh.org>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>,
        KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
        John Stultz <john.stultz@linaro.org>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        uclinux-dist-devel@blackfin.uclinux.org, linuxppc-dev@lists.ozlabs.org,
        linux-sh@vger.kernel.org, user-mode-linux-devel@lists.sourceforge.net,
        linux-mm@kvack.org
Subject: Re: [PATCH 08/10] um: Fix possible race on task->mm
References: <20120324102609.GA28356@lizard> <20120324103050.GH29067@lizard>
In-Reply-To: <20120324103050.GH29067@lizard>
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Am 24.03.2012 11:30, schrieb Anton Vorontsov:
> Checking for task->mm is dangerous as ->mm might disappear (exit_mm()
> assigns NULL under task_lock(), so tasklist lock is not enough).
>=20
> We can't use get_task_mm()/mmput() pair as mmput() might sleep,
> so let's take the task lock while we care about its mm.
>=20
> Note that we should also use find_lock_task_mm() to check all process'
> threads for a valid mm, but for uml we'll do it in a separate patch.
>=20
> Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>

Acked-by: Richard Weinberger <richard@nod.at>

Thanks,
//richard


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