linux-kernel - Re: Problem with freezable workqueues

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Message-ID: <20070228035149.GL29179@in.ibm.com>
Date:	Wed, 28 Feb 2007 09:21:49 +0530
From:	Srivatsa Vaddagiri <vatsa@...ibm.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Pavel Machek <pavel@....cz>, Gautham R Shenoy <ego@...ibm.com>,
	Johannes Berg <johannes@...solutions.net>,
	LKML <linux-kernel@...r.kernel.org>,
	Oleg Nesterov <oleg@...sign.ru>
Subject: Re: Problem with freezable workqueues

On Wed, Feb 28, 2007 at 08:31:13AM +0530, Srivatsa Vaddagiri wrote:
> This problem (of kthread_stopping a frozen thread) was there when we
> implemented freezer-based cpu hotplug. We worked around that in the
> callbacks by thawing the worker thread first before kthread_stopping it,
> which is working pretty neatly.
> 
> Should that fix the issue? 

In addition to thawing worker thread before kthread_stopping it, there
are minor changes required in worker threads, to check for
is_cpu_offline(bind_cpu) when they come out of refrigerator and jump to
wait_to_die if so (ex: softirq.c).

I guess you would need these changes before freezer-based hotplug is
merged, in which case Gautham can send those patches out first.

-- 
Regards,
vatsa
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