linux-kernel - Re: [2.6.21.1] resume doesn't run suspended kernel?

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Message-Id: <1180444425.20718.33.camel@nigel.suspend2.net>
Date:	Tue, 29 May 2007 23:13:45 +1000
From:	Nigel Cunningham <nigel@...el.suspend2.net>
To:	Pavel Machek <pavel@....cz>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Bill Davidsen <davidsen@....com>,
	Linux Kernel M/L <linux-kernel@...r.kernel.org>
Subject: Re: [2.6.21.1] resume doesn't run suspended kernel?

Hi.

On Tue, 2007-05-29 at 14:40 +0200, Pavel Machek wrote:
> On Tue 2007-05-29 14:03:07, Rafael J. Wysocki wrote:
> > On Tuesday, 29 May 2007 13:29, Pavel Machek wrote:
> > > Hi!
> > > 
> > > > > Yup.  Don't we do something like this for the (ACPI-based) suspend to RAM
> > > > > already?
> > > > 
> > > > Yeah, I was thinking about this overnight too. It should be doable. In
> > > > addition to what we already do, I think you'd want:
> > > > 
> > > > - to copy the assembly to do the copying to a safe page;
> > > > - to put the location of the cpu state that was saved in the image
> > > > header so that it can be used after the data is copied back;
> > > 
> > > ...alternatively, we can just rely on copy routine (and its data) not
> > > changing frequently.
> > > 
> > > > - to copy the nosave data to a 'safe' page.
> > > > 
> > > > What else?
> > > 
> > > page directories need to be on a safe place, too.
> > 
> > They are already.
> 
> ...but will that place still be safe when we use other version of
> kernel?

They'll be in the image too, won't they? Failing that, the information
could be stored in the image header.

> Anyway, pagedirs are on the safe place, right? That means that we
> swsusp should no longer clash with page allocation debugging... 

You mean DEBUG_PAGEALLOC? That can be overcome easily - I have code in
current Suspend2 that works with DEBUG_PAGEALLOC. I handle the page
fault, mapping the page and setting a flag in the fault handler to tell
the atomic copy code to unmap the page again once it has been copied.

Regards,

Nigel

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