linux-kernel - Re: [PATCH 06/16] freezer: make exiting tasks properly unfreezable

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Message-ID: <20110827103534.GK2632@htj.dyndns.org>
Date:	Sat, 27 Aug 2011 12:35:34 +0200
From:	Tejun Heo <tj@...nel.org>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Oleg Nesterov <oleg@...hat.com>, menage@...gle.com,
	linux-kernel@...r.kernel.org, arnd@...db.de
Subject: Re: [PATCH 06/16] freezer: make exiting tasks properly unfreezable

Hello, Rafael.

On Fri, Aug 26, 2011 at 11:09:38PM +0200, Rafael J. Wysocki wrote:
> > One thing I'm curious about is how many drivers do we have left which
> > depend on freezer as opposed to implementing proper quiescing
> > mechanism using PM hooks?  Are there still a lot left?
> 
> There is a number of drivers that use freezable workqueues and that's
> prefectly valid in my view.  Beyond that, may suspend/resume routines
> depend on the freezer to some extent, because they assume that user
> space won't talk to the driver while they are being run.
> 
> Do you mean any other kind of dependence?

I still feel a bit unsure about depending on freezer as escaping them
unintentionally seems a bit too easy (e.g. schedule_work() for delayed
processing) and as drivers need to implement responses to PM events
anyway, I think implementing the support explicitly has lesser chance
of causing obscure bugs which are difficult to reproduce.  Anyways,
something to discuss some other day, I guess.

Thanks.

-- 
tejun
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