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Date: Wed, 23 Apr 2025 15:23:33 -0700
From: Jakub Kicinski <kuba@kernel.org>
To: Bui Quang Minh <minhquangbui99@gmail.com>
Cc: virtualization@lists.linux.dev, "Michael S. Tsirkin" <mst@redhat.com>,
 Jason Wang <jasowang@redhat.com>, Xuan Zhuo <xuanzhuo@linux.alibaba.com>,
 Andrew Lunn <andrew+netdev@lunn.ch>, Eric Dumazet <edumazet@google.com>,
 Paolo Abeni <pabeni@redhat.com>, Alexei Starovoitov <ast@kernel.org>,
 Daniel Borkmann <daniel@iogearbox.net>, Jesper Dangaard Brouer
 <hawk@kernel.org>, John Fastabend <john.fastabend@gmail.com>, Eugenio
 =?UTF-8?B?UMOpcmV6?= <eperezma@redhat.com>, "David S. Miller"
 <davem@davemloft.net>, netdev@vger.kernel.org,
 linux-kernel@vger.kernel.org, bpf@vger.kernel.org
Subject: Re: [PATCH v4 4/4] selftests: net: add a virtio_net deadlock
 selftest
Message-ID: <20250423152333.68117196@kernel.org>
In-Reply-To: <aac402b4-d04c-4d7e-91c8-ab6c20c9a74d@gmail.com>
References: <20250417072806.18660-1-minhquangbui99@gmail.com>
	<20250417072806.18660-5-minhquangbui99@gmail.com>
	<20250422184151.2fb4fffe@kernel.org>
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On Wed, 23 Apr 2025 22:20:41 +0700 Bui Quang Minh wrote:
> I've tried to make the setup_xsk into each test. However, I've an issue=20
> that the XDP socket destruct waits for an RCU grace period as I see this=
=20
> sock's flag SOCK_RCU_FREE is set. So if we start the next test right=20
> away, we can have the error when setting up XDP socket again because=20
> previous XDP socket has not unbound the network interface's queue yet. I=
=20
> can resolve the issue by putting the sleep(1) after closing the socket=20
> in xdp_helper:
>=20
> diff --git a/tools/testing/selftests/net/lib/xdp_helper.c=20
> b/tools/testing/selftests/net/lib/xdp_helper.c
> index f21536ab95ba..e882bb22877f 100644
> --- a/tools/testing/selftests/net/lib/xdp_helper.c
> +++ b/tools/testing/selftests/net/lib/xdp_helper.c
> @@ -162,5 +162,6 @@ int main(int argc, char **argv)
>  =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 */
>=20
>  =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 close(sock_fd);
> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 sleep(1);
>  =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 return 0;
>  =C2=A0}
>=20
> Do you think it's enough or do you have a better suggestion here?

Interesting :S What errno does the kernel return? EBUSY?
Perhaps we could loop for a second retrying the bind()
if kernel returns EBUSY in case it's just a socket waiting
to be cleaned up?