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

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Message-ID: <53b94412-c550-4d90-9275-5b087609b8e3@gmail.com>
Date: Fri, 4 Apr 2025 16:43:44 +0700
From: Bui Quang Minh <minhquangbui99@...il.com>
To: virtualization@...ts.linux.dev
Cc: "Michael S . Tsirkin" <mst@...hat.com>, Jason Wang <jasowang@...hat.com>,
 Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, Andrew Lunn <andrew+netdev@...n.ch>,
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>, Alexei Starovoitov <ast@...nel.org>,
 Daniel Borkmann <daniel@...earbox.net>,
 Jesper Dangaard Brouer <hawk@...nel.org>,
 John Fastabend <john.fastabend@...il.com>,
 Eugenio Pérez <eperezma@...hat.com>,
 "David S . Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH] virtio-net: disable delayed refill when setting up xdp

On 4/3/25 17:43, Bui Quang Minh wrote:
> 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 <minhquangbui99@...il.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.

I've sent a new patch here: 
https://lore.kernel.org/virtualization/20250404093903.37416-1-minhquangbui99@gmail.com/T/#u. 
As the commit title has changed a little bit, I don't use v2 tag.

Thank you,
Quang Minh.