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    SubjectRe: [linux-pm] Re: [PATCH 0/2] Kexec jump: The first step to kexec base hibernation
    Date
    On Friday, 13 July 2007 16:37, Alan Stern wrote:
    > On Fri, 13 Jul 2007, Rafael J. Wysocki wrote:
    >
    > > > I missed this discussion. is this idea to suspend, write to disk, but
    > > > leave things in ram so that if you wakeup soon enough you have everything
    > > > for ram, but if you don't and the battery dies you can restore from disk?
    > > >
    > > > if so I think it's a mistake to mix the two. it would be better to just
    > > > suspend to ram, and wake up once in a while to check the battery state and
    > > > when the battery gets low enough do the suspend to disk.
    > > >
    > > > otherwise you end up mixing the requirements of the two types of suspend,
    > > > which is how things got so ugly in the first place.
    > >
    > > Not necessarily. If we don't put devices into low power states before creating
    > > the image, that should work just fine (quiesce devices, create the image or
    > > kexec the new kernel, reprobe devices, save the image, suspend to RAM,
    > > resume from RAM, continue - or restore from the image if power failed in the
    > > meantime). Still, for this purpose, both kernels need to be able to handle the
    > > same set of devices.
    >
    > Why?
    >
    > Suppose the kexec kernel can't handle some device. The normal kernel
    > has already quiesced the device, so it will remain quiescent while the
    > kexec kernel runs and throughout the suspend. When the regular kernel
    > regains control the device will be ready for use. I don't see any
    > problem.

    On an ACPI system the device may be in a power state that doesn't allow us to
    enter S3 (in theory, that is).

    Greetings,
    Rafael


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