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    SubjectRe: [PATCH -v2] freezer: check OOM kill while being frozen
    On 10/17, Michal Hocko wrote:
    >
    > I think we should rather get back to __thaw_task here.

    Yes, agreed.

    > Andrew could you replace the previous version by this one, please?

    Yes, that patch should be dropped...


    And can't resist... please look at
    http://marc.info/?l=linux-kernel&m=138427535430827 ;)

    > --- a/kernel/freezer.c
    > +++ b/kernel/freezer.c
    > @@ -45,13 +45,28 @@ bool freezing_slow_path(struct task_struct *p)
    > if (pm_nosig_freezing || cgroup_freezing(p))
    > return true;
    >
    > - if (pm_freezing && !(p->flags & PF_KTHREAD))
    > + if (!(p->flags & PF_KTHREAD))

    Why? Doesn't this mean that try_to_freeze() can race with thaw_processes()
    and then this task can be frozen for no reazon?

    > +static bool should_thaw_current(bool check_kthr_stop)
    > +{
    > + if (!freezing(current))
    > + return true;
    > +
    > + if (check_kthr_stop && kthread_should_stop())
    > + return true;
    > +
    > + /* It might not be safe to check TIF_MEMDIE for pm freeze. */
    > + if (cgroup_freezing(current) && test_thread_flag(TIF_MEMDIE))

    I still think that the comment should tell more to explain why this
    is not safe.

    And if this is not safe, it is not clear how/why cgroup_freezing() can
    save us, both pm_freezing and CGROUP_FREEZING can be true?

    And I think that this TIF_MEMDIE should go into freezing_slow_path(),
    so we do not even need should_thaw_current().

    This also looks more safe to me. Suppose that a task does

    while (try_to_freeze())
    ;

    Yes, this is pointless but correct. And in fact I think this pattern
    is possible. If this task is killed by OOM, it will spin forever.

    Oleg.



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