On Thu, Apr 26, 2007 at 08:44:36PM +0400, Oleg Nesterov wrote:
> On 04/26, Jarek Poplawski wrote:
> >
> > On Wed, Apr 25, 2007 at 04:47:14PM +0400, Oleg Nesterov wrote:
> > ...
> > > > > > + spin_lock_irq(&cwq->lock);
> > > > > > + /* CPU_DEAD in progress may change cwq */
> > > > > > + if (likely(cwq == get_wq_data(work))) {
> > > > > > + list_del_init(&work->entry);
> > > > > > + __set_bit(WORK_STRUCT_PENDING, work_data_bits(work));
> > > > > > + retry = try_to_del_timer_sync(&dwork->timer) < 0;
> > > > > > + }
> > > > > > + spin_unlock_irq(&cwq->lock);
> > > > > > + } while (unlikely(retry));
> > >
> > > > 1. If delayed_work_timer_fn of this work is fired and is waiting
> > > > on the above spin_lock then, after above spin_unlock, the work
> > > > will be queued.
> > >
> > > No, in that case try_to_del_timer_sync() returns -1.
> >
> > Yes. But I think it's safe only after moving work_clear_pending
> > in run_workqueue under a lock; probably otherwise there is a
> > possibility this flag could be cleared, after above unlock.
>
> It doesn't matter in this particular case because we are going to retry
> anyway. But yes, this patch moves work_clear_pending() under lock, because
> otherwise it could be cleared by run_workqueue() if this work is about
> to be executed, but was already deleted from list.
...and it seems to be the same what I meant...
I wanted only to make agree (now it's only for historical reasons)
the lock on _PENDING could matter in run_workqueue.
Jarek P.
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