linux-kernel - Re: [PATCH -tip] fix race between stop_two_cpus and stop

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Message-ID: <527399A0.304@redhat.com>
Date:	Fri, 01 Nov 2013 08:08:00 -0400
From:	Prarit Bhargava <prarit@...hat.com>
To:	Rik van Riel <riel@...hat.com>
CC:	Mel Gorman <mgorman@...e.de>, peterz@...radead.org,
	mingo@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH -tip] fix race between stop_two_cpus and stop_cpus



On 11/01/2013 07:36 AM, Rik van Riel wrote:
> On 11/01/2013 07:08 AM, Mel Gorman wrote:
>> On Thu, Oct 31, 2013 at 04:31:44PM -0400, Rik van Riel wrote:
>>> There is a race between stop_two_cpus, and the global stop_cpus.
>>>
>>
>> What was the trigger for this? I want to see what was missing from my own
>> testing. I'm going to go out on a limb and guess that CPU hotplug was also
>> running in the background to specifically stress this sort of rare condition.
>> Something like running a standard test with the monitors/watch-cpuoffline.sh
>> from mmtests running in parallel.
> 
> AFAIK the trigger was a test that continuously loads and
> unloads kernel modules, while doing other stuff.
>

With this patch in place the module load/unload test ran for ~16 hours without
failure.  Without the patch the test usually fails in 5-10 minutes.

Tested-by: Prarit Bhargava <prarit@...hat.com>

P.
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