linux-kernel - Re: Hibernation Redesign

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Message-ID: <87y7hpvbpr.fsf@jbms.ath.cx>
Date:	Mon, 09 Jul 2007 11:27:44 -0400
From:	Jeremy Maitin-Shepard <jbms@....edu>
To:	Oliver Neukum <oliver@...kum.org>
Cc:	Pavel Machek <pavel@....cz>, Nick Piggin <nickpiggin@...oo.com.au>,
	Al Boldi <a1426z@...ab.com>, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: Hibernation Redesign

Oliver Neukum <oliver@...kum.org> writes:

> Am Montag, 9. Juli 2007 schrieb Jeremy Maitin-Shepard:
>> Oliver Neukum <oliver@...kum.org> writes:
>> 
>> [snip]
>> 
>> > Hm, once the new kernel is booted, this decision is irrevocable, isn't it?
>> > Is there any way to deal with errors by handing control back?
>> 
>> Returning to the old kernel can be done by telling drivers to set the
>> hardware to the appropriate state, then copying the backed up memory
>> back to the beginning of physical memory, and finally jumping to the old
>> kernel.  It would be much like what is done to resume from hibernation.

> If you can do that, why load a new kernel image?

The challenges in doing that are analogous to the challenges in
suspending to RAM, for which it has been agreed that drivers should be
fixed such that the freezer is not necessary.

The hard part of hibernate is not creating the snapshot; rather, the
hard part is writing the snapshot, and allowing the user some
flexibility in how and where the snapshot is written.  The kdump
approach allows complete flexibility in writing the snapshot
(essentially any kernel or user space facility can be used), while not
interfering at all with the snapshot state.

-- 
Jeremy Maitin-Shepard
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