Re: Hibernation considerations

[david@lang.hm]

On Sun, 15 Jul 2007, Alan Stern wrote:

> On Sun, 15 Jul 2007, Al Boldi wrote:
>
> > Alan Stern wrote:
> > > On Sun, 15 Jul 2007, Al Boldi wrote:
>
> > > > This should be the responsibility of the kexec'd hibernating kernel.
> > > > Note though in (6), the normal kernel takes care of preparing devices,
> > > > then the hibernating kernel dumps the image and either calls S4 or S3.
> > > > On resume from S3 it can immediately switch over to the normal kernel,
> > > > and from S4 the known bootup would occur.
> > >
> > > Is it really that simple?  Somehow I doubt it.  In order for some
> > > devices to remain available for the kexec'd kernel to use, they cannot
> > > be suspended at the ACPI level.  So the kexec'd kernel will have to
> > > handle the ACPI requirements for those devices.  Likewise, it would
> > > have to handle the ACPI interactions which need to be done after all
> > > devices are prepared for the transition to S3 or S4.
> >
> > Ok, after applying the latest kexec patches, I was able to use the kexec'd
> > kernel to suspend to ram and resume to the normal kernel, while working
> > under a full-blown X session.  It went without a hitch.  All that is needed
> > now are the dump/restore hibernation-image routines.
>
> That's exactly my point.  While doing suspend-to-RAM from a kexec'd
> kernel may be simple, saving the hibernation image will add
> complications.

suspend-to-RAM should not involve kexec, the only reason for doing the 
kexec to to get a seperate userspace to use for suspend-to-disk operations 
instead of trying to partially freeze the sustem and keep useing it.

David Lang
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