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    SubjectRe: suspend2 merge (was Re: [Suspend2-devel] Re: CFS and suspend2: hang in atomic copy)


    On Thu, 26 Apr 2007, Nigel Cunningham wrote:
    > >
    > > And name *one* thing that have in common.
    >
    > Set/reset the scsi transaction id thingy? Hibernation didn't work with
    > SCSI for a long time precisely because that support was missing.

    And by "hibernation", you mean what? You mean "snapshot + shutdown",
    right?

    Think about it for five seconds, and then ask yourself: at which point in
    the "snapshot + shutdown" sequence would you actually tell a disk to shut
    down?

    If you said "snapshot", then you'd be *wrong*.

    That's my _point_. The snapshot() function should not (and MUST NOT) tell
    disks to shut down, because unlike suspend(), we're still going to _use_
    those disks afterwards (why? To write out the snapshot image!).

    In other words, the act of creating a snapshot has *nothing* to do with
    suspend.

    Now, after you've created (and written out) the snapshot, what do you
    actually end up doing?

    That's right - you end up _shutting down_ the machine, and yes, as part
    of the _shutdown_ sequence you may actually end up doing a lot of the
    things that a suspend would do. But that's long *after* you've actually
    done the "snapshot" part, and has absolutely nothing to do with it.

    That's where I started: whole "suspend to disk" thing actually has _more_
    to do with "shutdown" than with "suspend".

    Linus
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