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    SubjectRe: hibernate/suspend-to-disk: to turn power or not?
    Pavel Machek wrote:
    >> I'm looking at the uswsusp source (while the kernel compiles),
    >> and have a question here. Is it possible to call some external
    >> application (typically a shell script) to do the final work after
    >> when the image has been written? I mean in principle - I
    >> understand there are some limitations here, but I don't know
    >> which exactly.
    > No, you can't exec() anything. That would write mtime back to disk and
    > cause badness.

    Now that's.. interesting.

    s2disk writes to a swap device/file, which should update
    mtime of this device node/file. Isn't it something which
    also causes the same badness?

    Also, if the only concern is mtime update, what's really
    wrong with it? I mean, regardless of whether such update
    will finally hit the disk or not, there's not much difference
    really - it updates just mtime field, and there should be
    no harm in that. Unless such update first goes to a
    journal (in a journalling filesystem) - which DOES modify
    some on-disk structures.

    >> it typically involves writing/reading something to/from
    >> a given serial port (/dev/ttySxx), or to an USB device,

    > Create, and link s2disk to it?

    And what's the difference here again? We'll open a serial
    port and write something to it - which, again, will update
    mtime of that device node. Unless the said node is on a
    tmpfs, exactly the same badness will happen. Not all the
    world is udev, after all.

    So I don't get the reason why we can't exec something here,
    still. (And, for example, call splashy commands as external
    processes, instead of linking all this cruft into s2disk and

    What I'm thinking about here is - s2ram mlock()s its memory.
    If it will fork/exec something, that something will obviously
    NOT be locked like that. Is it of some concern? Probably
    not, because that something will be executed after we've
    taken the snapshot.


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      Last update: 2008-02-01 08:19    [W:0.040 / U:15.184 seconds]
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