linux-kernel - Re: [linux-pm] [PATCH -mm] kexec jump -v9

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Date:	Thu, 20 Mar 2008 23:45:23 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Pavel Machek <pavel@....cz>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Alan Stern <stern@...land.harvard.edu>,
	nigel@...el.suspend2.net,
	Kexec Mailing List <kexec@...ts.infradead.org>,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-pm@...ts.linux-foundation.org,
	Vivek Goyal <vgoyal@...hat.com>
Subject: Re: [linux-pm] [PATCH -mm] kexec jump -v9

On Thursday, 20 of March 2008, Pavel Machek wrote:
> On Tue 2008-03-18 21:25:27, Eric W. Biederman wrote:
> > Alan Stern <stern@...land.harvard.edu> writes:
> > 
> > > On Wed, 19 Mar 2008, Rafael J. Wysocki wrote:
> > >
> > >> Well, I've been saying that for I-don't-remember-how-long: on my box, if you
> > >> use S5 instead of entering S4, the fan doesn't work correctly after the
> > >> resume.  Plain and simple.
> > >> 
> > >> Perhaps there's a problem with our ACPI drivers that causes this to happen,
> > >> but I have no idea what that can be at the moment.
> > >
> > > IMO it would be worthwhile to track this down.  It's a clear indication 
> > > that something is wrong somewhere.
> > >
> > > Could it be connected with the way the boot kernel hands control over
> > > to the image kernel?  Presumably ACPI isn't prepared to deal with that
> > > sort of thing during a boot from S5.  It would have to be fooled into
> > > thinking the two kernels were one and the same.
> > 
> > It should be easy to test if it is a hand over problem, by turning off
> > the laptop by placing it in S5 (shutdown -h now) and then booting same
> > kernel again.
> 
> Feel free to help with testing.
> 
> I believe ACPI is simply getting confused by us overwriting memory
> with that from old image. I don't see how you can emulate it with
> shutdown.

Well, in fact ACPI has something called the NVS memory, which we're supposed
to restore during the resume and which we're not doing.  The problem may be
related to this.

I have fixing that on my todo list, but frankly there's many different things
in there. :-)

Thanks,
Rafael
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