linux-kernel - Re: [PATCH] Remove process freezer from suspend to RAM pathway

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Message-Id: <1183931688.3388.316.camel@localhost.localdomain>
Date:	Mon, 09 Jul 2007 07:54:48 +1000
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Alan Stern <stern@...land.harvard.edu>,
	Kyle Moffett <mrmacman_g4@....com>,
	Nigel Cunningham <nigel@...el.suspend2.net>,
	Pavel Machek <pavel@....cz>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	linux-kernel@...r.kernel.org, linux-pm@...ts.linux-foundation.org
Subject: Re: [PATCH] Remove process freezer from suspend to RAM pathway

On Sun, 2007-07-08 at 23:45 +0200, Rafael J. Wysocki wrote:
> 
> Workqueues are kernel threads and the creator decides if they are going to
> freeze.  There are only two freezable worqueues in the entire tree right now.

That and keventd workqueues... my point is you may well end up with
something in a workqueue doing things that should have been blocked
after the freeze.

> Actaully, I'm perfectly fine with that, as long as each task blocked by the
> driver due to suspend has PF_FROZEN (or something similar) set.  Then, at
> least theoretically, we'll be able to drop the freezer from the suspend code
> path and move it after device_suspend() (or the hibernation-specific
> equivalent) for hibernation (in that case there shouldn't be a problem with
> any task waiting on I/O while the freezer is running ;-)).

I don't see the need for a freezer for snapshot but that's a different
issue. (stop_machine looks good enough to me).

Ben

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