linux-kernel - Re: [PATCH 0/2] Kexec jump: The first step to kexec base hibernation

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Message-Id: <200707132255.39077.rjw@sisk.pl>
Date:	Fri, 13 Jul 2007 22:55:37 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Jeremy Maitin-Shepard <jbms@....edu>, david@...g.hm,
	"Huang, Ying" <ying.huang@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Pavel Machek <pavel@....cz>, nigel@...el.suspend2.net,
	linux-kernel@...r.kernel.org, linux-pm@...ts.linux-foundation.org,
	"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: Re: [PATCH 0/2] Kexec jump: The first step to kexec base hibernation

On Friday, 13 July 2007 17:50, Alan Stern wrote:
> On Fri, 13 Jul 2007, Rafael J. Wysocki wrote:
> 
> > Okay, I have thought it through and I think that, as an initial step, we can do
> > something like this:
> > 
> > - preload the image-saving kernel before hibernation
> > - in the hibernation code path replace device_suspend() with the shutting down of
> >   all devices without unregistering them (not very nice, but should be sufficient
> >   for a while)
> > - when we've called device_power_down() and save_processor_state(), jump to
> >   the image-saving kernel and let it run
> > - make the image-saving kernel set up everything, save the image without
> >   starting any user space (we may use the existing image-saving code for this
> >   purpose, with some modifications) and power off the system (or make it enter
> >   S4)
> > - use the existing restoration code to load the image and jump to the
> >   hibernated kernel
> > - in the restore code patch replace device_resume() with the reprobing of all
> >   devices.
> > 
> > Comments?
> 
> I doubt that re-probing devices will work.  The probe routine won't 
> expect there to be any registered children, so it will try to 
> re-register them.

I didn't mean to use .probe() for that.  I just used the term "reprobe" as
similar to "reinit", but not exactly the same.

> On the other hand, post_restore methods could be written to expect 
> something like this.

Yes, that's what I'm thinking of.

Greetings,
Rafael


-- 
"Premature optimization is the root of all evil." - Donald Knuth
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