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From: "Rafael J. Wysocki" <rjw@sisk.pl>
To: Tejun Heo <tj@kernel.org>
Subject: Re: [PATCH 1/8] PM: Add suspend block api.
Date: Fri, 21 May 2010 00:27:31 +0200
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Cc: Oleg Nesterov <oleg@redhat.com>,
       Arve =?iso-8859-1?q?Hj=F8nnev=E5g?= <arve@android.com>,
       linux-pm@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
       Alan Stern <stern@rowland.harvard.edu>, Len Brown <len.brown@intel.com>,
       Pavel Machek <pavel@ucw.cz>, Randy Dunlap <rdunlap@xenotime.net>,
       Jesse Barnes <jbarnes@virtuousgeek.org>, Magnus Damm <damm@igel.co.jp>,
       Nigel Cunningham <nigel@tuxonice.net>,
       Cornelia Huck <cornelia.huck@de.ibm.com>,
       Ming Lei <tom.leiming@gmail.com>, Wu Fengguang <fengguang.wu@intel.com>,
       Andrew Morton <akpm@linux-foundation.org>,
       Maxim Levitsky <maximlevitsky@gmail.com>, linux-doc@vger.kernel.org
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On Thursday 20 May 2010, Tejun Heo wrote:
> Hello,
> 
> (sorry about late reply)
> 
> On 04/30/2010 07:26 PM, Oleg Nesterov wrote:
> > Currently _cpu_down() can't flush and/or stop the frozen cwq->thread.
> > 
> > IIRC this is fixable, but needs the nasty complications. We should
> > thaw + stop the frozen cwq->thread, then move the pending works to
> > another CPU.
> 
> Oh, this isn't an issue w/ cmwq.  While frozen all new works are
> collected into per-cpu delayed worklist and while frozen trustee in
> charge of the cpu will keep waiting.  Once thawed, trustee will
> execute all works including the delayed ones unbound to any cpu.

So, does it require any intrusive changes to make it possible to create
multithread freezable workqueues?

Rafael