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From: Jeremy Maitin-Shepard <jbms@cmu.edu>
To: david@lang.hm
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>, Alan Stern <stern@rowland.harvard.edu>,
       LKML <linux-kernel@vger.kernel.org>,
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       Al Boldi <a1426z@gawab.com>
Subject: Re: Hibernation considerations
References: <Pine.LNX.4.44L0.0707171416120.3728-100000@iolanthe.rowland.org>
	<200707172217.01890.rjw@sisk.pl>
	<Pine.LNX.4.64.0707171328450.2467@asgard.lang.hm>
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Date: Tue, 17 Jul 2007 16:54:08 -0400
In-Reply-To: <Pine.LNX.4.64.0707171328450.2467@asgard.lang.hm>
	(david@lang.hm's message of "Tue\, 17 Jul 2007 13\:34\:24 -0700 \(PDT\)")
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david@lang.hm writes:

[snip]

> this is where we disagree.

> why not? if all that the hibernated kernel does is to suspend-to-ram and makes
> no changes to disks or TCP connections anything that it does do would be lost if
> power were to fail and you instead did a restore from disk.

It would be okay to switch the "hibernated" kernel in order to
e.g. initiate a suspend to ram provided that everything is done
atomically with interrupts off, for instance.  It is not clear, though,
that it is possible to suspend to ram atomically like that.

There is also the question of what state the devices will be in when
switching back from the "save image" kernel to the "hibernated" kernel.

[snip]

-- 
Jeremy Maitin-Shepard