On Thu, Jun 25, 2009 at 09:28:27AM -0400, Gregory Haskins wrote:
> @@ -65,25 +134,39 @@ irqfd_wakeup(wait_queue_t *wait, unsigned mode, int 
> sync, void *key)
>       unsigned long flags = (unsigned long)key;
>  
>       /*
> -      * Assume we will be called with interrupts disabled
> +      * Called with interrupts disabled
>        */
>       if (flags & POLLIN)
> -             /*
> -              * Defer the IRQ injection until later since we need to
> -              * acquire the kvm->lock to do so.
> -              */
> +             /* An event has been signaled, inject an interrupt */
>               schedule_work(&irqfd->inject);
>  
>       if (flags & POLLHUP) {
> -             /*
> -              * for now, just remove ourselves from the list and let
> -              * the rest dangle.  We will fix this up later once
> -              * the races in eventfd are fixed
> -              */
> +             /* The eventfd is closing, detach from KVM */
> +             struct kvm *kvm = irqfd->kvm;
> +             unsigned long flags;
> +
>               __remove_wait_queue(irqfd->wqh, &irqfd->wait);
> -             irqfd->wqh = NULL;
> +
> +             spin_lock_irqsave(&kvm->irqfds.lock, flags);
> +
> +             if (irqfd->active) {
> +                     /*
> +                      * If the item is still active we can be sure that
> +                      * no-one else is trying to shutdown this object at
> +                      * the same time.
> +                      *
> +                      * Defer the shutdown to a thread so we can flush
> +                      * all remaining inject jobs.  We use a slow-work
> +                      * item to prevent a deadlock against the work-queue
> +                      */
> +                     irqfd_deactivate(irqfd);
> +                     slow_work_enqueue(&irqfd->shutdown);

Greg, in your patch for slow-work module removal, you write:
  "Callers must ensure that their module has at least
  one reference held while the work is enqueued."
  Where does this guarantee come from, in this case?

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