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[PATCH] virito: Use auto rcu_read macros

Dr. David Alan Gilbert (git) posted 1 patch 4 years, 6 months ago
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git fetch https://github.com/patchew-project/qemu tags/patchew/20191014175440.152609-1-dgilbert@redhat.com
Maintainers: "Michael S. Tsirkin" <mst@redhat.com>
hw/virtio/virtio.c | 46 ++++++++++++++++------------------------------
1 file changed, 16 insertions(+), 30 deletions(-)
[PATCH] virito: Use auto rcu_read macros
Posted by Dr. David Alan Gilbert (git) 4 years, 6 months ago 
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>
---
 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
Re: [PATCH] virito: Use auto rcu_read macros
Posted by Dr. David Alan Gilbert 4 years, 6 months ago 
* 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
Re: [PATCH] virito: Use auto rcu_read macros
Posted by Michael S. Tsirkin 4 years, 5 months ago 
On Mon, Oct 14, 2019 at 06:54:40PM +0100, Dr. David Alan Gilbert (git) 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>

Can you rebase on top of packed ring support please?
They are in my queue now.


> ---
>  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
Re: [PATCH] virito: Use auto rcu_read macros
Posted by Dr. David Alan Gilbert 4 years, 5 months ago 
* Michael S. Tsirkin (mst@redhat.com) wrote:
> On Mon, Oct 14, 2019 at 06:54:40PM +0100, Dr. David Alan Gilbert (git) 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>
> 
> Can you rebase on top of packed ring support please?
> They are in my queue now.

Sent; fixed up in about the same way but not tested much.

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
Re: [PATCH] virito: Use auto rcu_read macros
Posted by Stefan Hajnoczi 4 years, 6 months ago 
On Mon, Oct 14, 2019 at 06:54:40PM +0100, Dr. David Alan Gilbert (git) 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>
> ---
>  hw/virtio/virtio.c | 46 ++++++++++++++++------------------------------
>  1 file changed, 16 insertions(+), 30 deletions(-)

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

Patchew 2.1-devel-0870f84

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