Re: [PATCH] slow_work_thread() should do the exclusive wait

Oleg Nesterov
2009-04-13T19:18:57Z

On 04/13, Trond Myklebust wrote:
>
> On Mon, 2009-04-13 at 20:17 +0200, Oleg Nesterov wrote:
> > slow_work_thread() sleeps on slow_work_thread_wq without WQ_FLAG_EXCLUSIVE,
> > this means that slow_work_enqueue()->__wake_up(nr_exclusive => 1) wakes up
> > all kslowd threads. Afaics this is not what we want, change slow_work_thread()
> > to use prepare_to_wait_exclusive().
> >
> > Signed-off-by: Oleg Nesterov <oleg@redhat.com>
> >
> > --- 6.30/kernel/slow-work.c~1_SW_EXCLUSIVE 2009-04-06 00:03:42.000000000 +0200
> > +++ 6.30/kernel/slow-work.c 2009-04-13 19:40:20.000000000 +0200
> > @@ -372,8 +372,8 @@ static int slow_work_thread(void *_data)
> > vsmax *= atomic_read(&slow_work_thread_count);
> > vsmax /= 100;
> >
> > - prepare_to_wait(&slow_work_thread_wq, &wait,
> > - TASK_INTERRUPTIBLE);
> > + prepare_to_wait_exclusive(&slow_work_thread_wq, &wait,
> > + TASK_INTERRUPTIBLE);
> > if (!freezing(current) &&
> > !slow_work_threads_should_exit &&
> > !slow_work_available(vsmax) &&
> >
>
> Should that really be TASK_INTERRUPTIBLE? I don't see anything obvious
> in the enclosing for(;;) loop that checks for or handles signals...

I guess TASK_INTERRUPTIBLE was chosen to not contribute to calc_load(),
nr_active() returns nr_running + nr_uninterruptible.

Oleg.