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    SubjectRe: [PATCH 3/6] oom: kill younger process first
    On Wed, 22 Jun 2011, KOSAKI Motohiro wrote:

    > diff --git a/include/linux/sched.h b/include/linux/sched.h
    > index e4e6d7b..392ff30 100644
    > --- a/include/linux/sched.h
    > +++ b/include/linux/sched.h
    > @@ -2257,6 +2257,9 @@ static inline unsigned long wait_task_inactive(struct task_struct *p,
    > #define next_task(p) \
    > list_entry_rcu((p)->tasks.next, struct task_struct, tasks)
    >
    > +#define prev_task(p) \
    > + list_entry((p)->tasks.prev, struct task_struct, tasks)
    > +
    > #define for_each_process(p) \
    > for (p = &init_task ; (p = next_task(p)) != &init_task ; )
    >
    > @@ -2269,6 +2272,14 @@ extern bool current_is_single_threaded(void);
    > #define do_each_thread(g, t) \
    > for (g = t = &init_task ; (g = t = next_task(g)) != &init_task ; ) do
    >
    > +/*
    > + * Similar to do_each_thread(). but two difference are there.
    > + * - traverse tasks reverse order (i.e. younger to older)
    > + * - caller must hold tasklist_lock. rcu_read_lock isn't enough
    > +*/
    > +#define do_each_thread_reverse(g, t) \
    > + for (g = t = &init_task ; (g = t = prev_task(g)) != &init_task ; ) do
    > +
    > #define while_each_thread(g, t) \
    > while ((t = next_thread(t)) != g)
    >

    I've already ack'd the patch, but if there is another version posted as a
    result of our discussion of using euid in the heuristic, I think it would
    be helpful to reiterate in this comment that, like do_each_thread(),
    do_each_thread_reverse() is not break-safe either. It might end up
    preventing a bug down the road.


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