linux-kernel - hibernation/snapshot design [was Re: [PATCH] Remove process freezer from suspend to RAM pathway]

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Message-ID: <20070708221315.GF5401@elf.ucw.cz>
Date:	Mon, 9 Jul 2007 00:13:15 +0200
From:	Pavel Machek <pavel@....cz>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Alan Stern <stern@...land.harvard.edu>,
	Kyle Moffett <mrmacman_g4@....com>,
	Nigel Cunningham <nigel@...el.suspend2.net>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	linux-kernel@...r.kernel.org, linux-pm@...ts.linux-foundation.org
Subject: hibernation/snapshot design [was Re: [PATCH] Remove process freezer from suspend to RAM pathway]

Hi!

> > 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).

Freezer is not needed for snapshot -- it is needed so that we can
write out the snapshot to disk without the need for special
drivers/block/simple-ide-for-suspend.c. (We are doing snapshot, then
write to disk from userland code in uswsusp).
								Pavel 

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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