diff options
| author | Tom Lendacky <tahm@linux.vnet.ibm.com> | 2010-02-08 10:10:01 -0600 |
|---|---|---|
| committer | Anthony Liguori <aliguori@us.ibm.com> | 2010-02-23 14:07:58 -0600 |
| commit | 7ebc79037c5f426bfb08cc506670bf7dd3912430 (patch) | |
| tree | b382405b9c6bcd087131b3f176a026b75bbcb658 | |
| parent | ea299062eb66dba86b390b7e0f414f6a4e41f11f (diff) | |
| download | qemu-7ebc79037c5f426bfb08cc506670bf7dd3912430.tar.gz | |
virtio-net: fix network stall under load
Fix a race condition where qemu finds that there are not enough virtio
ring buffers available and the guest make more buffers available before
qemu can enable notifications.
Signed-off-by: Tom Lendacky <toml@us.ibm.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
(cherry picked from commit 06b1297017415ae6a07a0e97ad7d8e90b2d95823)
| -rw-r--r-- | hw/virtio-net.c | 10 |
1 files changed, 9 insertions, 1 deletions
diff --git a/hw/virtio-net.c b/hw/virtio-net.c index 2f201ffc76..d8a1629dc3 100644 --- a/hw/virtio-net.c +++ b/hw/virtio-net.c @@ -384,7 +384,15 @@ static int virtio_net_has_buffers(VirtIONet *n, int bufsize) (n->mergeable_rx_bufs && !virtqueue_avail_bytes(n->rx_vq, bufsize, 0))) { virtio_queue_set_notification(n->rx_vq, 1); - return 0; + + /* To avoid a race condition where the guest has made some buffers + * available after the above check but before notification was + * enabled, check for available buffers again. + */ + if (virtio_queue_empty(n->rx_vq) || + (n->mergeable_rx_bufs && + !virtqueue_avail_bytes(n->rx_vq, bufsize, 0))) + return 0; } virtio_queue_set_notification(n->rx_vq, 0); |