When we fail to refill the receive buffers, we schedule a delayed worker
to retry later. However, this worker creates some concurrency issues.
For example, when the worker runs concurrently with virtnet_xdp_set,
both need to temporarily disable queue's NAPI before enabling again.
Without proper synchronization, a deadlock can happen when
napi_disable() is called on an already disabled NAPI. That
napi_disable() call will be stuck and so will the subsequent
napi_enable() call.
To simplify the logic and avoid further problems, we will instead retry
refilling in the next NAPI poll.
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]
Suggested-by: Xuan Zhuo <[email protected]>
Signed-off-by: Bui Quang Minh <[email protected]>
---
drivers/net/virtio_net.c | 48 +++++++++++++++++++++-------------------
1 file changed, 25 insertions(+), 23 deletions(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 1bb3aeca66c6..f986abf0c236 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -3046,16 +3046,16 @@ static int virtnet_receive(struct receive_queue *rq,
int budget,
else
packets = virtnet_receive_packets(vi, rq, budget, xdp_xmit,
&stats);
+ u64_stats_set(&stats.packets, packets);
if (rq->vq->num_free > min((unsigned int)budget,
virtqueue_get_vring_size(rq->vq)) / 2) {
- if (!try_fill_recv(vi, rq, GFP_ATOMIC)) {
- spin_lock(&vi->refill_lock);
- if (vi->refill_enabled)
- schedule_delayed_work(&vi->refill, 0);
- spin_unlock(&vi->refill_lock);
- }
+ if (!try_fill_recv(vi, rq, GFP_ATOMIC))
+ /* We need to retry refilling in the next NAPI poll so
+ * we must return budget to make sure the NAPI is
+ * repolled.
+ */
+ packets = budget;
}
- u64_stats_set(&stats.packets, packets);
u64_stats_update_begin(&rq->stats.syncp);
for (i = 0; i < ARRAY_SIZE(virtnet_rq_stats_desc); i++) {
size_t offset = virtnet_rq_stats_desc[i].offset;
@@ -3230,9 +3230,10 @@ static int virtnet_open(struct net_device *dev)
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);
+ /* Pre-fill rq agressively, to make sure we are ready to
+ * get packets immediately.
+ */
+ try_fill_recv(vi, &vi->rq[i], GFP_KERNEL);
err = virtnet_enable_queue_pair(vi, i);
if (err < 0)
@@ -3472,16 +3473,15 @@ static void __virtnet_rx_resume(struct virtnet_info *vi,
struct receive_queue *rq,
bool refill)
{
- bool running = netif_running(vi->dev);
- bool schedule_refill = false;
+ if (netif_running(vi->dev)) {
+ /* Pre-fill rq agressively, to make sure we are ready to get
+ * packets immediately.
+ */
+ if (refill)
+ try_fill_recv(vi, rq, GFP_KERNEL);
- 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);
+ }
}
static void virtnet_rx_resume_all(struct virtnet_info *vi)
@@ -3829,11 +3829,13 @@ static int virtnet_set_queues(struct virtnet_info *vi,
u16 queue_pairs)
}
succ:
vi->curr_queue_pairs = queue_pairs;
- /* virtnet_open() will refill when device is going to up. */
- spin_lock_bh(&vi->refill_lock);
- if (dev->flags & IFF_UP && vi->refill_enabled)
- schedule_delayed_work(&vi->refill, 0);
- spin_unlock_bh(&vi->refill_lock);
+ if (dev->flags & IFF_UP) {
+ local_bh_disable();
+ for (int i = 0; i < vi->curr_queue_pairs; ++i)
+ virtqueue_napi_schedule(&vi->rq[i].napi, vi->rq[i].vq);
+
+ local_bh_enable();
+ }
return 0;
}
--
2.43.0
