On Wed, 29 Oct 2014 10:32:10 -0400 Tejun Heo <t...@kernel.org> wrote:
> Hello, Neil.
>
> On Wed, Oct 29, 2014 at 05:26:08PM +1100, NeilBrown wrote:
> > Hi Tejun,
> > I haven't tested this patch yet so this really is an 'RFC'.
> > In general ->nr_active should only be accessed under the pool->lock,
> > but a miss-read here will at most cause a very occasional 100ms delay so
> > shouldn't be a big problem. The only thread likely to change ->nr_active is
> > this thread, so such a delay would be extremely unlikely.
> >
> > Thanks,
> > NeilBrown
> >
> >
> > diff --git a/kernel/workqueue.c b/kernel/workqueue.c
> > index 09b685daee3d..d0a8b101c5d9 100644
> > --- a/kernel/workqueue.c
> > +++ b/kernel/workqueue.c
> > @@ -2244,16 +2244,18 @@ repeat:
> > spin_lock_irq(&pool->lock);
> > rescuer->pool = pool;
> >
> > - /*
> > - * Slurp in all works issued via this workqueue and
> > - * process'em.
> > - */
> > - WARN_ON_ONCE(!list_empty(&rescuer->scheduled));
> > - list_for_each_entry_safe(work, n, &pool->worklist, entry)
> > - if (get_work_pwq(work) == pwq)
> > - move_linked_works(work, scheduled, &n);
> > + do {
> > + /*
> > + * Slurp in all works issued via this workqueue and
> > + * process'em.
> > + */
> > + WARN_ON_ONCE(!list_empty(&rescuer->scheduled));
> > + list_for_each_entry_safe(work, n, &pool->worklist,
> > entry)
> > + if (get_work_pwq(work) == pwq)
> > + move_linked_works(work, scheduled, &n);
> >
> > - process_scheduled_works(rescuer);
> > + process_scheduled_works(rescuer);
> > + } while (need_more_worker(pool) && pwq->nr_active);
>
> need_more_worker(pool) is always true for unbound pools as long as
> there are work items queued, so the above condition may stay true
> longer than it needs to.
Because ->nr_running isn't maintained for WORKER_UNBOUND (which is part of
WORKER_NOT_RUNNING) - got it.
> Given that workder depletion is pool-wide
> event, maybe it'd make sense to trigger rescuers immediately while
> workers are in short supply? e.g. while there's a manager stuck in
> maybe_create_worker() with the mayday timer already triggered?
So what if I change "need_more_worker" to "need_to_create_worker" ?
Then it will stop as soon as there in an idle worker thread.
That is the condition that keeps maybe_create_worker() looping.
??
Thanks,
NeilBrown
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