linux-kernel - Re: Problem with freezable workqueues

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Date:	Wed, 28 Feb 2007 23:36:57 +0530
From:	Gautham R Shenoy <ego@...ibm.com>
To:	Johannes Berg <johannes@...solutions.net>
Cc:	Oleg Nesterov <oleg@...sign.ru>, "Rafael J. Wysocki" <rjw@...k.pl>,
	Pavel Machek <pavel@....cz>,
	LKML <linux-kernel@...r.kernel.org>,
	Srivatsa Vaddagiri <vatsa@...ibm.com>
Subject: Re: Problem with freezable workqueues

On Wed, Feb 28, 2007 at 12:36:52AM +0100, Johannes Berg wrote:
> On Wed, 2007-02-28 at 02:28 +0300, Oleg Nesterov wrote:
> 
> > Ugh. I know nothing, nothing, nothing about suspend. I'll try to guess.
> > 
> >    Commit: ed746e3b18f4df18afa3763155972c5835f284c5
> 
> > Yes? with the patch above, _cpu_down() called _after_ freeze_processes() ???
> 
> perfect :)
> See also my original mail and the thread:
> http://thread.gmane.org/gmane.linux.power-management.general/4314
> 
> > How about other kthread_stop()s ? For example, kernel/softirq.c:cpu_callback() ?
> 
> I'd they should be affected as well. For me, I guess I haven't run into
> them because xfs is enough to freeze the box ;) As for Rafael, I don't
> know why he isn't seeing that... I haven't been able to test this patch
> on my quad powermac so far unfortunately, been sick and away from the
> machine. I'll probably be able to test tomorrow.

They will be affected. In our first implemetentation of 
general "cpu_down after freeze"(http://lkml.org/lkml/2007/2/14/107)
we had a new state known CPU_DEAD_KILL_THREADS, 
the notifications for which were being sent
*after* we thawed the processes in __cpu_down.

However, in the version which we are working on, we are thawing processes
individually in CPU_DEAD before cleaning/stopping them.

I haven't observed any bad lockups/freeze chills with this approach. 
But I need to test it a bit more before posting them.

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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