linux-kernel - Re: [PATCH v4] stop_machine: Disable preemption after queueing stopper threads

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Message-ID: <df84aa9229cf0789fd4f729b06161be9@codeaurora.org>
Date:   Tue, 17 Jul 2018 12:34:34 -0700
From:   isaacm@...eaurora.org
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     matt@...eblueprint.co.uk, mingo@...nel.org, tglx@...utronix.de,
        bigeasy@...utronix.de, linux-kernel@...r.kernel.org,
        psodagud@...eaurora.org, gregkh@...uxfoundation.org,
        pkondeti@...eaurora.org, stable@...r.kernel.org
Subject: Re: [PATCH v4] stop_machine: Disable preemption after queueing
 stopper threads

Alright, we will make a new patch for this. Thanks for the feedback.

Thanks,
Isaac Manjarres
On 2018-07-17 11:34, Peter Zijlstra wrote:
> On Tue, Jul 17, 2018 at 09:30:17AM -0700, Isaac J. Manjarres wrote:
>> After cpu_stop_queue_two_works() queues the cpu_stop works
>> for the stopper threads, it releases the locks held for
>> both threads, which enables preemption, which allows the
>> following race condition to occur:
> 
> 
> Does not apply because an earlier version is already applied.
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/commit/kernel/stop_machine.c?id=9fb8d5dc4b649dd190e1af4ead670753e71bf907
> 
> if there still is a problem, please send a new patch that describes the
> remaining problem.