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

Gregory Haskins
2009-06-02T17:42:20Z

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Davide Libenzi wrote:
> 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
>
>
>
Indeed. Thanks for catching that!

-Greg

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