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Message-ID: <19f34abd0811110647y2a00cfbfr2b219a5aa1b3ac9f@mail.gmail.com>
Date: Tue, 11 Nov 2008 15:47:56 +0100
From: "Vegard Nossum" <vegard.nossum@gmail.com>
To: "Ingo Molnar" <mingo@elte.hu>, "Rafael J. Wysocki" <rjw@sisk.pl>
Subject: Re: [Bug #11989] Suspend failure on NForce4-based boards due to chanes in stop_machine
Cc: "Heiko Carstens" <heiko.carstens@de.ibm.com>,
       "Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
       "Kernel Testers List" <kernel-testers@vger.kernel.org>,
       "Rusty Russell" <rusty@rustcorp.com.au>,
       "Peter Zijlstra" <a.p.zijlstra@chello.nl>,
       "Oleg Nesterov" <oleg@redhat.com>,
       "Dmitry Adamushko" <dmitry.adamushko@gmail.com>,
       "Andrew Morton" <akpm@linux-foundation.org>
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On Tue, Nov 11, 2008 at 11:52 AM, Ingo Molnar <mingo@elte.hu> wrote:
> [ Cc:-ed workqueue/locking/suspend-race-condition experts. ]
>
> Seems like the new kernel/stop_machine.c logic has a race for the test
> sequence above. (Below is the bisected commit again, maybe the race is
> visible via email review as well.)

I try again.

I think that the test for stop_machine_data in stop_cpu() should not
have been moved from __stop_machine(). Because now cpu_online_map may
change in-between calls to stop_cpu() (if the callback tries to
online/offline CPUs), and the end result may be different.

Maybe?


Vegard
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