Calling napi_disable() on an already disabled napi can cause the
deadlock. In commit 4bc12818b363 ("virtio-net: disable delayed refill
when pausing rx"), to avoid the deadlock, when pausing the RX in
virtnet_rx_pause[_all](), we disable and cancel the delayed refill work.
However, in the virtnet_rx_resume_all(), we enable the delayed refill
work too early before enabling all the receive queue napis.
The deadlock can be reproduced by running
selftests/drivers/net/hw/xsk_reconfig.py with multiqueue virtio-net
device and inserting a cond_resched() inside the for loop in
virtnet_rx_resume_all() to increase the success rate. Because the worker
processing the delayed refilled work runs on the same CPU as
virtnet_rx_resume_all(), a reschedule is needed to cause the deadlock.
In real scenario, the contention on netdev_lock can cause the
reschedule.
This fixes the deadlock by ensuring all receive queue's napis are
enabled before we enable the delayed refill work in
virtnet_rx_resume_all() and virtnet_open().
Fixes: 4bc12818b363 ("virtio-net: disable delayed refill when pausing rx")
Reported-by: Paolo Abeni <[email protected]>
Closes:
https://netdev-ctrl.bots.linux.dev/logs/vmksft/drv-hw-dbg/results/400961/3-xdp-py/stderr
Cc: [email protected]
Signed-off-by: Bui Quang Minh <[email protected]>
---
Changes in v2:
- Move try_fill_recv() before rx napi_enable()
- Link to v1:
https://lore.kernel.org/netdev/[email protected]/
---
drivers/net/virtio_net.c | 71 +++++++++++++++++++++++++---------------
1 file changed, 45 insertions(+), 26 deletions(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 8e04adb57f52..4e08880a9467 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -3214,21 +3214,31 @@ static void virtnet_update_settings(struct virtnet_info
*vi)
static int virtnet_open(struct net_device *dev)
{
struct virtnet_info *vi = netdev_priv(dev);
+ bool schedule_refill = false;
int i, err;
- enable_delayed_refill(vi);
-
+ /* - We must call try_fill_recv before enabling napi of the same receive
+ * queue so that it doesn't race with the call in virtnet_receive.
+ * - We must enable and schedule delayed refill work only when we have
+ * enabled all the receive queue's napi. Otherwise, in refill_work, we
+ * have a deadlock when calling napi_disable on an already disabled
+ * napi.
+ */
for (i = 0; i < vi->max_queue_pairs; i++) {
if (i < vi->curr_queue_pairs)
/* Make sure we have some buffers: if oom use wq. */
if (!try_fill_recv(vi, &vi->rq[i], GFP_KERNEL))
- schedule_delayed_work(&vi->refill, 0);
+ schedule_refill = true;
err = virtnet_enable_queue_pair(vi, i);
if (err < 0)
goto err_enable_qp;
}
+ enable_delayed_refill(vi);
+ if (schedule_refill)
+ schedule_delayed_work(&vi->refill, 0);
+
if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_STATUS)) {
if (vi->status & VIRTIO_NET_S_LINK_UP)
netif_carrier_on(vi->dev);
@@ -3463,39 +3473,48 @@ static void virtnet_rx_pause(struct virtnet_info *vi,
struct receive_queue *rq)
__virtnet_rx_pause(vi, rq);
}
-static void __virtnet_rx_resume(struct virtnet_info *vi,
- struct receive_queue *rq,
- bool refill)
+static void virtnet_rx_resume_all(struct virtnet_info *vi)
{
- bool running = netif_running(vi->dev);
bool schedule_refill = false;
+ int i;
- if (refill && !try_fill_recv(vi, rq, GFP_KERNEL))
- schedule_refill = true;
- if (running)
- virtnet_napi_enable(rq);
-
- if (schedule_refill)
- schedule_delayed_work(&vi->refill, 0);
-}
+ if (netif_running(vi->dev)) {
+ /* See the comment in virtnet_open for the ordering rule
+ * of try_fill_recv, receive queue napi_enable and delayed
+ * refill enable/schedule.
+ */
+ for (i = 0; i < vi->max_queue_pairs; i++) {
+ if (i < vi->curr_queue_pairs)
+ if (!try_fill_recv(vi, &vi->rq[i], GFP_KERNEL))
+ schedule_refill = true;
-static void virtnet_rx_resume_all(struct virtnet_info *vi)
-{
- int i;
+ virtnet_napi_enable(&vi->rq[i]);
+ }
- enable_delayed_refill(vi);
- for (i = 0; i < vi->max_queue_pairs; i++) {
- if (i < vi->curr_queue_pairs)
- __virtnet_rx_resume(vi, &vi->rq[i], true);
- else
- __virtnet_rx_resume(vi, &vi->rq[i], false);
+ enable_delayed_refill(vi);
+ if (schedule_refill)
+ schedule_delayed_work(&vi->refill, 0);
}
}
static void virtnet_rx_resume(struct virtnet_info *vi, struct receive_queue
*rq)
{
- enable_delayed_refill(vi);
- __virtnet_rx_resume(vi, rq, true);
+ bool schedule_refill = false;
+
+ if (netif_running(vi->dev)) {
+ /* See the comment in virtnet_open for the ordering rule
+ * of try_fill_recv, receive queue napi_enable and delayed
+ * refill enable/schedule.
+ */
+ if (!try_fill_recv(vi, rq, GFP_KERNEL))
+ schedule_refill = true;
+
+ virtnet_napi_enable(rq);
+
+ enable_delayed_refill(vi);
+ if (schedule_refill)
+ schedule_delayed_work(&vi->refill, 0);
+ }
}
static int virtnet_rx_resize(struct virtnet_info *vi,
--
2.43.0
