Re: [PATCH] virito: Use auto rcu_read macros

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Dr. David Alan Gilbert (git) (dgilbert@redhat.com) wrote:
> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> 
> Use RCU_READ_LOCK_GUARD and WITH_RCU_READ_LOCK_GUARD
> to replace the manual rcu_read_(un)lock calls.
> 
> I think the only change is virtio_load which was missing unlocks
> in error paths; those end up being fatal errors so it's not
> that important anyway.
> 
> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

Oops, I've typo'd virito in the title again...

Dave

> ---
>  hw/virtio/virtio.c | 46 ++++++++++++++++------------------------------
>  1 file changed, 16 insertions(+), 30 deletions(-)
> 
> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> index 527df03bfd..15ae9da60b 100644
> --- a/hw/virtio/virtio.c
> +++ b/hw/virtio/virtio.c
> @@ -337,7 +337,7 @@ void virtio_queue_set_notification(VirtQueue *vq, int enable)
>          return;
>      }
>  
> -    rcu_read_lock();
> +    RCU_READ_LOCK_GUARD();
>      if (virtio_vdev_has_feature(vq->vdev, VIRTIO_RING_F_EVENT_IDX)) {
>          vring_set_avail_event(vq, vring_avail_idx(vq));
>      } else if (enable) {
> @@ -349,7 +349,6 @@ void virtio_queue_set_notification(VirtQueue *vq, int enable)
>          /* Expose avail event/used flags before caller checks the avail idx. */
>          smp_mb();
>      }
> -    rcu_read_unlock();
>  }
>  
>  int virtio_queue_ready(VirtQueue *vq)
> @@ -393,9 +392,8 @@ int virtio_queue_empty(VirtQueue *vq)
>          return 0;
>      }
>  
> -    rcu_read_lock();
> +    RCU_READ_LOCK_GUARD();
>      empty = vring_avail_idx(vq) == vq->last_avail_idx;
> -    rcu_read_unlock();
>      return empty;
>  }
>  
> @@ -530,10 +528,9 @@ void virtqueue_flush(VirtQueue *vq, unsigned int count)
>  void virtqueue_push(VirtQueue *vq, const VirtQueueElement *elem,
>                      unsigned int len)
>  {
> -    rcu_read_lock();
> +    RCU_READ_LOCK_GUARD();
>      virtqueue_fill(vq, elem, len, 0);
>      virtqueue_flush(vq, 1);
> -    rcu_read_unlock();
>  }
>  
>  /* Called within rcu_read_lock().  */
> @@ -624,7 +621,7 @@ void virtqueue_get_avail_bytes(VirtQueue *vq, unsigned int *in_bytes,
>          return;
>      }
>  
> -    rcu_read_lock();
> +    RCU_READ_LOCK_GUARD();
>      idx = vq->last_avail_idx;
>      total_bufs = in_total = out_total = 0;
>  
> @@ -719,7 +716,6 @@ done:
>      if (out_bytes) {
>          *out_bytes = out_total;
>      }
> -    rcu_read_unlock();
>      return;
>  
>  err:
> @@ -869,7 +865,7 @@ void *virtqueue_pop(VirtQueue *vq, size_t sz)
>      if (unlikely(vdev->broken)) {
>          return NULL;
>      }
> -    rcu_read_lock();
> +    RCU_READ_LOCK_GUARD();
>      if (virtio_queue_empty_rcu(vq)) {
>          goto done;
>      }
> @@ -977,7 +973,6 @@ void *virtqueue_pop(VirtQueue *vq, size_t sz)
>      trace_virtqueue_pop(vq, elem, elem->in_num, elem->out_num);
>  done:
>      address_space_cache_destroy(&indirect_desc_cache);
> -    rcu_read_unlock();
>  
>      return elem;
>  
> @@ -1680,13 +1675,10 @@ static bool virtio_should_notify(VirtIODevice *vdev, VirtQueue *vq)
>  
>  void virtio_notify_irqfd(VirtIODevice *vdev, VirtQueue *vq)
>  {
> -    bool should_notify;
> -    rcu_read_lock();
> -    should_notify = virtio_should_notify(vdev, vq);
> -    rcu_read_unlock();
> -
> -    if (!should_notify) {
> -        return;
> +    WITH_RCU_READ_LOCK_GUARD() {
> +        if (!virtio_should_notify(vdev, vq)) {
> +            return;
> +        }
>      }
>  
>      trace_virtio_notify_irqfd(vdev, vq);
> @@ -1718,13 +1710,10 @@ static void virtio_irq(VirtQueue *vq)
>  
>  void virtio_notify(VirtIODevice *vdev, VirtQueue *vq)
>  {
> -    bool should_notify;
> -    rcu_read_lock();
> -    should_notify = virtio_should_notify(vdev, vq);
> -    rcu_read_unlock();
> -
> -    if (!should_notify) {
> -        return;
> +    WITH_RCU_READ_LOCK_GUARD() {
> +        if (!virtio_should_notify(vdev, vq)) {
> +            return;
> +        }
>      }
>  
>      trace_virtio_notify(vdev, vq);
> @@ -2241,7 +2230,7 @@ int virtio_load(VirtIODevice *vdev, QEMUFile *f, int version_id)
>          vdev->start_on_kick = true;
>      }
>  
> -    rcu_read_lock();
> +    RCU_READ_LOCK_GUARD();
>      for (i = 0; i < num; i++) {
>          if (vdev->vq[i].vring.desc) {
>              uint16_t nheads;
> @@ -2289,7 +2278,6 @@ int virtio_load(VirtIODevice *vdev, QEMUFile *f, int version_id)
>              }
>          }
>      }
> -    rcu_read_unlock();
>  
>      return 0;
>  }
> @@ -2422,21 +2410,19 @@ void virtio_queue_set_last_avail_idx(VirtIODevice *vdev, int n, uint16_t idx)
>  
>  void virtio_queue_restore_last_avail_idx(VirtIODevice *vdev, int n)
>  {
> -    rcu_read_lock();
> +    RCU_READ_LOCK_GUARD();
>      if (vdev->vq[n].vring.desc) {
>          vdev->vq[n].last_avail_idx = vring_used_idx(&vdev->vq[n]);
>          vdev->vq[n].shadow_avail_idx = vdev->vq[n].last_avail_idx;
>      }
> -    rcu_read_unlock();
>  }
>  
>  void virtio_queue_update_used_idx(VirtIODevice *vdev, int n)
>  {
> -    rcu_read_lock();
> +    RCU_READ_LOCK_GUARD();
>      if (vdev->vq[n].vring.desc) {
>          vdev->vq[n].used_idx = vring_used_idx(&vdev->vq[n]);
>      }
> -    rcu_read_unlock();
>  }
>  
>  void virtio_queue_invalidate_signalled_used(VirtIODevice *vdev, int n)
> -- 
> 2.23.0
> 
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK