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

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Date:	Thu, 20 Mar 2008 19:01:56 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
cc:	Pavel Machek <pavel@....cz>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	<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 Thu, 20 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.

No, it can't be.  ACPI won't expect the NVS memory to be restored 
following an S5-shutdown.  In fact, as far as ACPI is concerned, 
resuming from an S5-type hibernation should not be considered a resume 
at all but just an ordinary reboot.  All ACPI-related memory areas 
in the boot kernel should be passed directly through to the image 
kernel.

Alan Stern

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