On Mon, Mar 6, 2017 at 4:28 AM, Jason Wang <jasow...@redhat.com> wrote:
>
>
> On 2017年03月03日 22:39, Willem de Bruijn wrote:
>>
>> +void vhost_signal(struct vhost_dev *dev, struct vhost_virtqueue *vq);
>> +static enum hrtimer_restart vhost_coalesce_timer(struct hrtimer *timer)
>> +{
>> + struct vhost_virtqueue *vq =
>> + container_of(timer, struct vhost_virtqueue, ctimer);
>> +
>> + if (mutex_trylock(&vq->mutex)) {
>> + vq->coalesce_frames = vq->max_coalesce_frames;
>> + vhost_signal(vq->dev, vq);
>> + mutex_unlock(&vq->mutex);
>> + }
>> +
>> + /* TODO: restart if lock failed and not held by handle_tx */
>> + return HRTIMER_NORESTART;
>> +}
>> +
>
>
> Then we may lose an interrupt forever if no new tx request? I believe we
> need e.g vhost_poll_queue() here.
Absolutely, I need to fix this. The common case for failing to grab
the lock is competition with handle_tx. With careful coding we can
probably avoid scheduling another run with vhost_poll_queue in
the common case.
Your patch v7 cancels the pending hrtimer at the start of handle_tx.
I need to reintroduce that, and also only schedule a timer at the end
of handle_tx, not immediately when vq->coalesce_frames becomes
non-zero.
