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    SubjectRe: [linux-pm] Re: Hibernation considerations
    On Fri, 20 Jul 2007, Alan Stern wrote:

    > On Fri, 20 Jul 2007, Milton Miller wrote:
    >
    >>> We can't do this unless we have frozen tasks (this way, or another)
    >>> before
    >>> carrying out the entire operation.
    >>
    >> What can't we do? We've already worked with the drivers to quesce the
    >> hardware and put any information to resume the device in ram. Now we
    >> ask them to put their device in low power mode so we can go to sleep.
    >> Even if we schedule, the only thing userspace could touch is memory.
    >
    > Userspace can submit I/O requests. Someone will have to audit every
    > driver to make sure that such I/O requests don't cause a quiesced
    > device to become active. If the device is active, it will make the
    > memory snapshot inconsistent with the on-device data.

    assuming this is the suspend-from-ram after a kexec back from the
    write-to-disk kernel I don't think you are correct.

    when doing a suspend-to-ram you get to a point where you just don't use
    any userspace. from that point on you are just walking the device tree
    putting things into low-power mode. This is the point where we are talking
    about jumping to.

    david Lang
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