linux-kernel - Re: [PATCH 01/21] workqueue: fix race condition in schedule_on_each

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Date:	Tue, 17 Nov 2009 09:04:56 +0200
From:	Avi Kivity <avi@...hat.com>
To:	Frederic Weisbecker <fweisbec@...il.com>
CC:	Tejun Heo <tj@...nel.org>, linux-kernel@...r.kernel.org,
	jeff@...zik.org, mingo@...e.hu, akpm@...ux-foundation.org,
	jens.axboe@...cle.com, rusty@...tcorp.com.au,
	cl@...ux-foundation.org, dhowells@...hat.com,
	arjan@...ux.intel.com, torvalds@...ux-foundation.org,
	peterz@...radead.org, andi@...stfloor.org,
	Andi Kleen <ak@...ux.intel.com>,
	Oleg Nesterov <oleg@...hat.com>
Subject: Re: [PATCH 01/21] workqueue: fix race condition in	schedule_on_each_cpu()

On 11/17/2009 01:04 AM, Frederic Weisbecker wrote:
> On Tue, Nov 17, 2009 at 02:15:06AM +0900, Tejun Heo wrote:
>    
>> Commit 65a64464349883891e21e74af16c05d6e1eeb4e9 which allows
>> schedule_on_each_cpu() to be called from keventd added a race
>> condition.  schedule_on_each_cpu() may race with cpu hotplug and end
>> up executing the function twice on a cpu.
>>
>> Fix it by moving direct execution into the section protected with
>> get/put_online_cpus().  While at it, update code such that direct
>> execution is done after works have been scheduled for all other cpus
>> and drop unnecessary cpu != orig test from flush loop.
>>
>> Signed-off-by: Tejun Heo<tj@...nel.org>
>> Cc: Andi Kleen<ak@...ux.intel.com>
>> Cc: Oleg Nesterov<oleg@...hat.com>
>> ---
>>      
>
> Shouldn't this patch go to .32 ?
> This looks like an important fix.
>    

Is anything using preeempt notifier on affected architectures?

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.

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