Re: [KVM-RFC PATCH 2/2] kvm: use POLLHUP to close an irqfd instead of an explicit ioctl

Davide Libenzi
2009-06-02T17:22:20Z

On Tue, 2 Jun 2009, Gregory Haskins wrote:

> @@ -64,12 +101,28 @@ irqfd_wakeup(wait_queue_t *wait, unsigned mode, int sync, void *key)
> {
> struct _irqfd *irqfd = container_of(wait, struct _irqfd, wait);
>
> - /*
> - * The wake_up is called with interrupts disabled. Therefore we need
> - * to defer the IRQ injection until later since we need to acquire the
> - * kvm->lock to do so.
> - */
> - schedule_work(&irqfd->work);
> + switch ((unsigned long)key) {
> + case POLLIN:
> + /*
> + * The POLLIN wake_up is called with interrupts disabled.
> + * Therefore we need to defer the IRQ injection until later
> + * since we need to acquire the kvm->lock to do so.
> + */
> + schedule_work(&irqfd->inject);
> + break;
> + case POLLHUP:
> + /*
> + * The POLLHUP is called unlocked, so it theoretically should
> + * be safe to remove ourselves from the wqh
> + */
> + remove_wait_queue(irqfd->wqh, &irqfd->wait);
> + flush_work(&irqfd->inject);
> + irqfd_disconnect(irqfd);
> +
> + cleanup_srcu_struct(&irqfd->srcu);
> + kfree(irqfd);
> + break;
> + }

Since "key" is an event *bitmap*, you better be treating it as such. Do
not assume what eventfd delivers today (event bitmaps with only one bit
set). So this better be like:

if (key & POLLIN) {
...
}
if (key & POLLHUP) {
...
}

- Davide