linux-kernel - Re: [PATCH 3/2] fix flush_workqueue() vs CPU

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Message-ID: <20070104043046.GA15162@in.ibm.com>
Date:	Thu, 4 Jan 2007 10:00:46 +0530
From:	Gautham R Shenoy <ego@...ibm.com>
To:	Oleg Nesterov <oleg@...sign.ru>
Cc:	Gautham R Shenoy <ego@...ibm.com>, Andrew Morton <akpm@...l.org>,
	Ingo Molnar <mingo@...e.hu>,
	David Howells <dhowells@...hat.com>,
	Christoph Hellwig <hch@...radead.org>,
	linux-kernel@...r.kernel.org, dipankar@...ibm.com, vatsa@...ibm.com
Subject: Re: [PATCH 3/2] fix flush_workqueue() vs CPU_DEAD race

On Wed, Jan 03, 2007 at 08:26:57PM +0300, Oleg Nesterov wrote:
> 
> I thought that these patches don't depend on each other, flush_work/workueue
> don't care where cpu-hotplug takes workqueue_mutex, in CPU_LOCK_ACQUIRE or in
> CPU_UP_PREPARE case (or CPU_DEAD/CPU_LOCK_RELEASE for unlock).
> 
> Could you clarify? Just curious.

You are right. They don't depend on each other. 

The intention behind introducing CPU_LOCK_ACQUIRE and CPU_LOCK_RELEASE
was to have a standard place where the subsystems could acquire/release
the "cpu hotplug protection" mutex in the cpu_hotplug callback function.

The same can be acheived by acquiring these mutexes in
CPU_UP_PREPARE/CPU_DOWN_PREPARE etc. 

This is true for every subsystem that is cpu-hotplug aware.

> Oleg.
> 

Thanks and Regards
gautham.
-- 
Gautham R Shenoy
Linux Technology Center
IBM India.
"Freedom comes with a price tag of responsibility, which is still a bargain,
because Freedom is priceless!"
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