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    SubjectRe: [PATCH -mm 2/3] Freezer: Use wait queue instead of busy looping (updated)
    On 08/02, Rafael J. Wysocki wrote:
    >
    > @@ -171,6 +186,10 @@ static int try_to_freeze_tasks(int freez
    >
    > end_time = jiffies + TIMEOUT;
    > do {
    > + DEFINE_WAIT(wait);
    > +
    > + add_wait_queue(&refrigerator_waitq, &wait);

    Hmm. In that case I'd sugest to use prepare_to_wait(). This means that
    multiple wakeups from refrigerator() won't do unnecessary work, and

    > +
    > todo = 0;
    > read_lock(&tasklist_lock);
    > do_each_thread(g, p) {
    > @@ -189,7 +208,12 @@ static int try_to_freeze_tasks(int freez
    > todo++;
    > } while_each_thread(g, p);
    > read_unlock(&tasklist_lock);
    > - yield(); /* Yield is okay here */
    > +
    > + set_current_state(TASK_UNINTERRUPTIBLE);
    > + if (todo && !list_empty_careful(&wait.task_list))
    > + schedule_timeout(WAIT_TIME);

    we don't need to check list_empty_careful() before schedule, prepare_to_wait()
    sets TASK_UNINTERRUPTIBLE under wait_queue_head_t->lock.

    Still, I personally agree with Pavel. Perhaps it is better to just replace
    yield() with schedule_timeout(a_bit).

    Oleg.

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