From d5675bd204efd87a174eeea592de23c4c4e7f908 Mon Sep 17 00:00:00 2001 From: "Michael S. Tsirkin" Date: Thu, 24 Jun 2010 16:59:59 +0300 Subject: vhost: break out of polling loop on error When ring parsing fails, we currently handle this as ring empty condition. This means that we enable kicks and recheck ring empty: if this not empty, we re-start polling which of course will fail again. Instead, let's return a negative error code and stop polling. Signed-off-by: Michael S. Tsirkin --- drivers/vhost/net.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) (limited to 'drivers/vhost/net.c') diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c index 0f41c9195e9b..54096eef4840 100644 --- a/drivers/vhost/net.c +++ b/drivers/vhost/net.c @@ -98,7 +98,8 @@ static void tx_poll_start(struct vhost_net *net, struct socket *sock) static void handle_tx(struct vhost_net *net) { struct vhost_virtqueue *vq = &net->dev.vqs[VHOST_NET_VQ_TX]; - unsigned head, out, in, s; + unsigned out, in, s; + int head; struct msghdr msg = { .msg_name = NULL, .msg_namelen = 0, @@ -135,6 +136,9 @@ static void handle_tx(struct vhost_net *net) ARRAY_SIZE(vq->iov), &out, &in, NULL, NULL); + /* On error, stop handling until the next kick. */ + if (head < 0) + break; /* Nothing new? Wait for eventfd to tell us they refilled. */ if (head == vq->num) { wmem = atomic_read(&sock->sk->sk_wmem_alloc); @@ -192,7 +196,8 @@ static void handle_tx(struct vhost_net *net) static void handle_rx(struct vhost_net *net) { struct vhost_virtqueue *vq = &net->dev.vqs[VHOST_NET_VQ_RX]; - unsigned head, out, in, log, s; + unsigned out, in, log, s; + int head; struct vhost_log *vq_log; struct msghdr msg = { .msg_name = NULL, @@ -228,6 +233,9 @@ static void handle_rx(struct vhost_net *net) ARRAY_SIZE(vq->iov), &out, &in, vq_log, &log); + /* On error, stop handling until the next kick. */ + if (head < 0) + break; /* OK, now we need to know about added descriptors. */ if (head == vq->num) { if (unlikely(vhost_enable_notify(vq))) { -- cgit v1.2.3 From 7b3384fc30633738ae4eaf8e1bc6ce70470ced80 Mon Sep 17 00:00:00 2001 From: "Michael S. Tsirkin" Date: Thu, 1 Jul 2010 18:40:12 +0300 Subject: vhost: add unlikely annotations to error path patch 'break out of polling loop on error' caused a minor performance regression on my machine: recover that performance by adding a bunch of unlikely annotations in the error handling. Signed-off-by: Michael S. Tsirkin --- drivers/vhost/net.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'drivers/vhost/net.c') diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c index 54096eef4840..2406377a6e5e 100644 --- a/drivers/vhost/net.c +++ b/drivers/vhost/net.c @@ -137,7 +137,7 @@ static void handle_tx(struct vhost_net *net) &out, &in, NULL, NULL); /* On error, stop handling until the next kick. */ - if (head < 0) + if (unlikely(head < 0)) break; /* Nothing new? Wait for eventfd to tell us they refilled. */ if (head == vq->num) { @@ -234,7 +234,7 @@ static void handle_rx(struct vhost_net *net) &out, &in, vq_log, &log); /* On error, stop handling until the next kick. */ - if (head < 0) + if (unlikely(head < 0)) break; /* OK, now we need to know about added descriptors. */ if (head == vq->num) { -- cgit v1.2.3