Messages in this thread | | | Date | Thu, 2 Aug 2007 22:40:02 +0400 | From | Oleg Nesterov <> | Subject | Re: [PATCH -mm 2/3] Freezer: Use wait queue instead of busy looping (updated) |
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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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