Messages in this thread | | | From | "Rafael J. Wysocki" <> | Subject | Re: [PATCH -mm 2/3] Freezer: Use wait queue instead of busy looping (updated) | Date | Thu, 2 Aug 2007 23:13:32 +0200 |
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On Thursday, 2 August 2007 20:40, Oleg Nesterov wrote: > 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,
I'm not sure what you mean.
Do you mean that if we are TASK_UNINTERRUPTIBLE, then the first wake up should remove us from the queue?
> 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.
Yes.
> Still, I personally agree with Pavel. Perhaps it is better to just replace > yield() with schedule_timeout(a_bit).
Hmm, I think that we shouldn't wait if that's not necessary.
Greetings, Rafael
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