Date: Wed, 28 Feb 2007 08:31:13 +0530
From: Srivatsa Vaddagiri <vatsa@in.ibm.com>
To: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Pavel Machek <pavel@ucw.cz>, Gautham R Shenoy <ego@in.ibm.com>,
       Johannes Berg <johannes@sipsolutions.net>,
       LKML <linux-kernel@vger.kernel.org>, Oleg Nesterov <oleg@tv-sign.ru>
Subject: Re: Problem with freezable workqueues
Message-ID: <20070228030113.GJ29179@in.ibm.com>
Reply-To: vatsa@in.ibm.com
References: <200702272251.28844.rjw@sisk.pl>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <200702272251.28844.rjw@sisk.pl>
User-Agent: Mutt/1.5.11
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 983
Lines: 22

On Tue, Feb 27, 2007 at 10:51:27PM +0100, Rafael J. Wysocki wrote:
> We have a problem with freezable workqueues in 2.6.21-rc1 and in -mm
> (there are only two of them, in XFS, but still).  Namely, their worker threads
> deadlock with workqueue_cpu_callback() that gets called during the CPU hotplug,
> becuase workqueue_cpu_callback() tries to stop these threads while they are
> frozen (disable_nonboot_cpus() happens after we've frozen tasks).

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? 

-- 
Regards,
vatsa
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/