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    SubjectRe: [PATCH 0/2] Kexec jump: The first step to kexec base hibernation
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    On Mon, 2007-07-16 at 14:17 +0200, Rafael J. Wysocki wrote:
    > > is this a matter of running some test to find out, or is this a question
    > > for the kexec implemantors?
    >
    > Actually, I'd like someone to tell me. ;-)
    >
    > I've browsed the kexec code, but haven't found anything related to the devices
    > in it. Perhaps I didn't know where to look ...

    There are two stages for kexec. For "normal" kexec, first the
    sys_kexe_load is called to load the kernel image, then
    sys_reboot(LINUX_REBOOT_CMD_KEXEC) is called to boot the new kernel. The
    call chain is as follow:

    sys_reboot(LINUX_REBOOT_CMD_KEXEC)
    kernel_kexec
    kernel_restart_prepare
    device_shutdown
    machine_shutdown
    machine_kexec

    In device_shutdown, the dev->bus->shutdown or dev->driver->shutdown of
    every device is called to put device in quiescent state. In
    machine_kexec, the new kernel is booted.

    So, for normal kexec, there is no code path for device state saving and
    restoring. State of device can be restore after shutdown? I don't think
    so.

    > I think that the right approach is to separate devices' suspend from the
    > devices' hibernation-related operations FIRST. Then, many different approaches
    > to hibernation will be much easier to implement than they are now.
    >
    > I've been saying this for weeks now, but no one seems to listen frankly I'm
    > tired of repeating it:

    I agree with you on this. :)

    > If we want to improve things, let's do that IN AN ORDERED WAY. If everyone
    > will come up with a new idea every two days, we won't be able to get anything
    > actually _done_.

    Yes, and I am very glad to collaborate with everybody who is interested
    in this subject. But I think we should try to verify our idea with code
    as early as possible. Now, I am trying to implement a prototype of
    kexec/kdump based image writing/reading mechanism to verify the
    feasibility. (I suppose you are working on separating device suspend and
    device hibernate).

    What do you think about the pattern of collaboration?

    At last, thank you very much for your valuable reminding in the mail of
    "hibernation considerations".

    Best Regards,
    Huang Ying
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