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    SubjectRe: [RFC PATCH(Experimental) 0/4] Freezer based Cpu-hotplug
    On 02/18, Rafael J. Wysocki wrote:
    >
    > On Sunday, 18 February 2007 00:47, Oleg Nesterov wrote:
    > >
    > > However, this means that sys_vfork() makes impossible to freeze processes
    > > until child exits/execs. Not good.
    >
    > Yes, but this also is the current behavior.

    Yes, yes, I see.

    I forgot to say that we have another problem: coredumping.

    A thread which does do_coredump() send SIGKILL to ->mm users, and sleeps
    on ->mm->core_startup_done. Now it can't be frozen if sub-thread goes to
    refrigerator. I think this could be solved easily if we add a check to
    refrigerator() as you suggested for ->vfork_donw.

    > I think the real solution would be to use an interruptible completion in the
    > vfork code. It was discussed some time ago and, IIRC, Ingo had an experimental
    > patch that implemented it. Still, for the suspend this really is not an issue
    > in practice, so it wasn't merged.

    It is not (afaics) so trivial to do rightly, and with this change the parent
    will be seen as TASK_INTERRUPTIBLE even without freezer in progress.

    A very vague idea: what if parent will do

    current->flags |= PF_PLEASE_CONSIDER_ME_AS_FROZEN_BUT_SET_TIF_FREEZE
    wait_for_completion(&vfork);
    try_to_freeze();

    ?

    > It may be a good time to solve this problem now. :-)

    Yes, I think so :)

    Oleg.

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