Messages in this thread |  | | | Date | Thu, 26 Apr 2007 20:44:36 +0400 | | From | Oleg Nesterov <> | | Subject | Re: Fw: [PATCH -mm] workqueue: debug possible endless loop in cancel_rearming_delayed_work |
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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.
Oleg.
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