Re: [PATCH] virtio-net: disable delayed refill when setting up xdp

[Bui Quang Minh]

On 4/2/25 12:42, Bui Quang Minh wrote:
When setting up XDP for a running interface, we call napi_disable() on
the receive queue's napi. In delayed refill_work, it also calls
napi_disable() on the receive queue's napi. This can leads to deadlock
when napi_disable() is called on an already disabled napi. This commit
fixes this by disabling future and cancelling all inflight delayed
refill works before calling napi_disabled() in virtnet_xdp_set.
Fixes: 4941d472bf95 ("virtio-net: do not reset during XDP set")
Signed-off-by: Bui Quang Minh <minhquangbu...@gmail.com>
---
  drivers/net/virtio_net.c | 12 ++++++++++++
  1 file changed, 12 insertions(+)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 7e4617216a4b..33406d59efe2 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -5956,6 +5956,15 @@ static int virtnet_xdp_set(struct net_device *dev, 
struct bpf_prog *prog,
        if (!prog && !old_prog)
                return 0;
  
+	/*
+        * Make sure refill_work does not run concurrently to
+        * avoid napi_disable race which leads to deadlock.
+        */
+       if (netif_running(dev)) {
+               disable_delayed_refill(vi);
+               cancel_delayed_work_sync(&vi->refill);
+       }
+
        if (prog)
                bpf_prog_add(prog, vi->max_queue_pairs - 1);
  
@@ -6004,6 +6013,8 @@ static int virtnet_xdp_set(struct net_device *dev, struct bpf_prog *prog,
                        virtnet_napi_tx_enable(&vi->sq[i]);
                }
        }
+       if (netif_running(dev))
+               enable_delayed_refill(vi);
While doing some testing, it look likes that we must call try_fill_recv 
to resume the rx path. I'll do more testing and send a new v2 patch.
  
  	return 0;
  
@@ -6019,6 +6030,7 @@ static int virtnet_xdp_set(struct net_device *dev, struct bpf_prog *prog,
                        virtnet_napi_enable(&vi->rq[i]);
                        virtnet_napi_tx_enable(&vi->sq[i]);
                }
+               enable_delayed_refill(vi);
        }
        if (prog)
                bpf_prog_sub(prog, vi->max_queue_pairs - 1);