linux-kernel - Re: [PATCH 1/8] PM: Add suspend block api.

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Message-ID: <4BDA5B8B.50004@kernel.org>
Date:	Fri, 30 Apr 2010 06:24:43 +0200
From:	Tejun Heo <tj@...nel.org>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
CC:	Arve Hjønnevåg <arve@...roid.com>,
	linux-pm@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
	Alan Stern <stern@...land.harvard.edu>,
	Oleg Nesterov <oleg@...hat.com>,
	Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
	Randy Dunlap <rdunlap@...otime.net>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Magnus Damm <damm@...l.co.jp>,
	Nigel Cunningham <nigel@...onice.net>,
	Cornelia Huck <cornelia.huck@...ibm.com>,
	Ming Lei <tom.leiming@...il.com>,
	Wu Fengguang <fengguang.wu@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Maxim Levitsky <maximlevitsky@...il.com>,
	linux-doc@...r.kernel.org
Subject: Re: [PATCH 1/8] PM: Add suspend block api.

Hello,

On 04/29/2010 11:16 PM, Rafael J. Wysocki wrote:
>>> Also, we already have one PM workqueue.  It is used for runtime PM, but I guess
>>> it may be used just as well for the opportunistic suspend.  It is freezable,
>>> but would it hurt?
>>
>> No, it works, the freezable flag is just ignored when I call
>> pm_suspend and I don't run anything else on the workqueue while
>> threads are frozen. It does need to be a single threaded workqueue
>> though, so make sure you don't just change that.
> 
> Freezable workqueues have to be singlethread or else there will be unfixable
> races, so you can safely assume things will stay as they are in this respect.

Rafael, can you elaborate a bit more on this?  Just in case I missed
something while doing cmwq as it currently doesn't have such limit.

Thanks.

-- 
tejun
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