From: "Michael S. Tsirkin" <mst@redhat.com>
To: linux-kernel@vger.kernel.org
Cc: Jason Wang <jasowang@redhat.com>,
Alan Stern <stern@rowland.harvard.edu>,
Andrea Parri <andrea.parri@amarulasolutions.com>,
Will Deacon <will.deacon@arm.com>,
Peter Zijlstra <peterz@infradead.org>,
Boqun Feng <boqun.feng@gmail.com>,
Nicholas Piggin <npiggin@gmail.com>,
David Howells <dhowells@redhat.com>,
Jade Alglave <j.alglave@ucl.ac.uk>,
Luc Maranget <luc.maranget@inria.fr>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Akira Yokosawa <akiyks@gmail.com>,
Daniel Lustig <dlustig@nvidia.com>,
linux-arch@vger.kernel.org, netdev@vger.kernel.org,
virtualization@lists.linux-foundation.org
Subject: [PATCH RFC 4/4] virtio: use dependent_ptr_mb
Date: Wed, 2 Jan 2019 15:58:03 -0500 [thread overview]
Message-ID: <20190102205715.14054-5-mst@redhat.com> (raw)
In-Reply-To: <20190102205715.14054-1-mst@redhat.com>
Use dependent_ptr_mb which is - on some architectures -
more light-weight than an rmb.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
drivers/virtio/virtio_ring.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 814b395007b2..2d320396eff8 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -702,6 +702,7 @@ void *virtqueue_get_buf_ctx(struct virtqueue *_vq, unsigned int *len,
void *ret;
unsigned int i;
u16 last_used;
+ bool more;
START_USE(vq);
@@ -710,14 +711,15 @@ void *virtqueue_get_buf_ctx(struct virtqueue *_vq, unsigned int *len,
return NULL;
}
- if (!more_used(vq)) {
+ more = more_used(vq);
+ if (!more) {
pr_debug("No more buffers in queue\n");
END_USE(vq);
return NULL;
}
/* Only get used array entries after they have been exposed by host. */
- virtio_rmb(vq->weak_barriers);
+ vq = dependent_ptr_mb(vq, more);
last_used = (vq->last_used_idx & (vq->vring.num - 1));
i = virtio32_to_cpu(_vq->vdev, vq->vring.used->ring[last_used].id);
--
MST
next prev parent reply other threads:[~2019-01-02 20:58 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-02 20:57 [PATCH RFC 0/4] barriers using data dependency Michael S. Tsirkin
2019-01-02 20:57 ` [PATCH RFC 1/4] include/linux/compiler*.h: fix OPTIMIZER_HIDE_VAR Michael S. Tsirkin
2019-01-08 17:44 ` Nick Desaulniers
2019-01-08 18:50 ` Michael S. Tsirkin
2019-01-09 10:35 ` Miguel Ojeda
2019-01-09 14:50 ` Michael S. Tsirkin
2019-01-19 18:35 ` Miguel Ojeda
2019-01-20 14:43 ` Michael S. Tsirkin
2019-01-20 15:36 ` Miguel Ojeda
2019-01-10 2:36 ` Michael S. Tsirkin
2019-01-10 13:41 ` Dan Carpenter
2019-01-10 14:08 ` Michael S. Tsirkin
2019-01-02 20:57 ` [PATCH RFC 2/4] include/linux/compiler.h: allow memory operands Michael S. Tsirkin
2019-01-07 17:54 ` Will Deacon
2019-01-07 18:16 ` Michael S. Tsirkin
2019-01-02 20:57 ` [PATCH RFC 3/4] barriers: convert a control to a data dependency Michael S. Tsirkin
2019-01-02 21:00 ` Matthew Wilcox
2019-01-02 21:24 ` Michael S. Tsirkin
2019-01-07 3:58 ` Jason Wang
2019-01-07 4:23 ` Michael S. Tsirkin
2019-01-07 6:50 ` Jason Wang
2019-01-07 9:46 ` Peter Zijlstra
2019-01-07 13:36 ` Michael S. Tsirkin
2019-01-07 15:54 ` Peter Zijlstra
2019-01-07 16:22 ` Michael S. Tsirkin
2019-01-07 19:02 ` Paul E. McKenney
2019-01-07 19:13 ` Michael S. Tsirkin
2019-01-07 19:25 ` Paul E. McKenney
2019-01-02 20:58 ` Michael S. Tsirkin [this message]
2019-01-02 21:36 ` [PATCH RFC 0/4] barriers using " Alan Stern
2019-01-02 23:04 ` Michael S. Tsirkin
2019-01-03 15:11 ` Alan Stern
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