Linux Virtualization - Dec 2016 - [PATCH 2/2] vhost: remove unnecessary smp_mb from vhost_work_queue

Signed-off-by: Peng Tao <bergwolf at gmail.com>
---
 drivers/vhost/vsock.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
index 0c23b55..3e01d58 100644
--- a/drivers/vhost/vsock.c
+++ b/drivers/vhost/vsock.c
@@ -195,7 +195,6 @@ static int
 vhost_transport_send_pkt(struct virtio_vsock_pkt *pkt)
 {
 	struct vhost_vsock *vsock;
-	struct vhost_virtqueue *vq;
 	int len = pkt->len;
 
 	/* Find the vhost_vsock according to guest context id  */
@@ -205,8 +204,6 @@ vhost_transport_send_pkt(struct virtio_vsock_pkt *pkt)
 		return -ENODEV;
 	}
 
-	vq = &vsock->vqs[VSOCK_VQ_RX];
-
 	if (pkt->reply)
 		atomic_inc(&vsock->queued_replies);
 
-- 
2.7.4

test_and_set_bit() already implies a memory barrier.

Signed-off-by: Peng Tao <bergwolf at gmail.com>
---
 drivers/vhost/vhost.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index c6f2d89..2663543 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -261,8 +261,8 @@ void vhost_work_queue(struct vhost_dev *dev, struct
vhost_work *work)
 	if (!test_and_set_bit(VHOST_WORK_QUEUED, &work->flags)) {
 		/* We can only add the work to the list after we're
 		 * sure it was not in the list.
+		 * test_and_set_bit() implies a memory barrier.
 		 */
-		smp_mb();
 		llist_add(&work->node, &dev->work_list);
 		wake_up_process(dev->worker);
 	}
-- 
2.7.4

On Wed, Dec 07, 2016 at 05:52:18PM +0800, Peng Tao
wrote:
> Signed-off-by: Peng Tao <bergwolf at gmail.com>
> ---
>  drivers/vhost/vsock.c | 3 ---
>  1 file changed, 3 deletions(-)
Reviewed-by: Stefan Hajnoczi <stefanha at redhat.com>
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On Wed, Dec 07, 2016 at 05:52:19PM +0800, Peng Tao
wrote:
> test_and_set_bit() already implies a memory barrier.
> 
> Signed-off-by: Peng Tao <bergwolf at gmail.com>
> ---
>  drivers/vhost/vhost.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
Reviewed-by: Stefan Hajnoczi <stefanha at redhat.com>
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From: Peng Tao <bergwolf at gmail.com>
Date: Wed,  7 Dec 2016 17:52:18 +0800
> Signed-off-by: Peng Tao <bergwolf at gmail.com>
Applied.

From: Peng Tao <bergwolf at gmail.com>
Date: Wed,  7 Dec 2016 17:52:19 +0800
> test_and_set_bit() already implies a memory barrier.
> 
> Signed-off-by: Peng Tao <bergwolf at gmail.com>
Applied.