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    SubjectRe: [RFC][PATCH -mm] Freezer: Handle uninterruptible tasks
    On Sunday, 8 July 2007 14:09, Pavel Machek wrote:
    > Hi!
    > > > And then you will face the problem of a user task doing I/O during
    > > > hibernate after the atomic snapshot has been made.
    > >
    > > I don't think that this is possible in normal conditions. It would be possible
    > > if, for example, the task were waiting for an unavailable resource and that
    > > resource became available after the hibernation image had been created.
    > > In that case, however, to do any damage, the task would have to cause some
    > > filesystem-related data to be flushed in the same syscall (ie. before returning
    > > to user space).
    > I agree that it is relatively unlikely to trigger (if you avoid
    > freezing the tasks that were uninterruptible for long), but it will
    > trigger in error cases etc.

    Yes, it will.

    > > Such situations may be prevented by a mechanizm detecting if any uniterruptible
    > > and freezing task has been woken up after creating the image and aborting the
    > > hibernation in that cases. For this purpose, we only need to add an
    > > appropriate condition to try_to_wake_up() and make it start to trigger after,
    > > for example, enabling the nonboot CPUs.
    > I don't know how to do that mechanism... but if we knew where to trap
    > filesystem writes, we could simply freeze at that point, and at that
    > point only, no?

    From the image/filesystems integrity standpoint, yes, that should be


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