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Fri, 06 Nov 2026 18:09:18 -0800 (PST) Received: from localhost ([153.61.198.246]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3b105864375sm1156571a91.4.2026.11.06.18.09.17 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 06 Nov 2026 18:09:18 -0800 (PST) Content-Type: text/plain; charset=UTF-8 Date: Sat, 07 Nov 2026 02:09:17 +0000 Message-Id: Cc: "Michal Luczaj" , , , , , Subject: Re: [PATCH net v4 1/2] vsock/bpf: release sock lock while waiting for data in recvmsg From: "Alexei Starovoitov" To: , "Stefano Garzarella" , "Bobby Eshleman" , "David S. Miller" , "Eric Dumazet" , "Jakub Kicinski" , "Paolo Abeni" , "Simon Horman" , "Michael S. Tsirkin" In-Reply-To: <20261106-kbh3-1-022-fix-v2-v4-1-c7d36703814d@eldare.de> References: <20261106-kbh3-1-022-fix-v2-v4-0-c7d36703814d@eldare.de> <20261106-kbh3-1-022-fix-v2-v4-1-c7d36703814d@eldare.de> Content-Transfer-Encoding: 8bit X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 On Fri, Nov 06, 2026 at 01:57 PM Jerome Mohm via B4 Relay wrote: > example by a credit update. So the wait also loops until data arrives > or one of the native exits applies: a socket error, a local or peer > shutdown, a socket that is no longer connected, the timeout or a > pending signal. The loop alone, with the lock still held, keeps the > deadlock, so the fix needs both halves and stays one patch. No need for a 2nd copy of the return values. The old code returns true on RCV_SHUTDOWN. The psock queue is empty, so the caller goes to __vsock_recvmsg(), which picks the return value. tcp_bpf, udp_bpf and unix_bpf do the same. Do it for sk_err, peer_shutdown and sk_state too. __vsock_recvmsg() doesn't wait in any of these states. It handles len == 0, MSG_OOB and MSG_ERRQUEUE as well. The copy differs from a socket that is not in a sockmap in four cases. The diff differs in one, the last row: recv() no sockmap this series the diff ------------------------------ ------------ ------------ ----------- after a virtio reset -ENOTCONN -ECONNRESET -ENOTCONN after a reset, len == 0 -ENOTCONN 0 -ENOTCONN after a reset, MSG_OOB -ENOTCONN -EOPNOTSUPP -ENOTCONN after peer shutdown, SO_INQ on 0 + SCM_INQ 0 0 + SCM_INQ asleep when the reset comes -ECONNRESET -ECONNRESET -ENOTCONN Instead of patches 1 and 2 (compile tested only): diff --git a/net/vmw_vsock/vsock_bpf.c b/net/vmw_vsock/vsock_bpf.c index 9049d26..3cf017d 100644 --- a/net/vmw_vsock/vsock_bpf.c +++ b/net/vmw_vsock/vsock_bpf.c @@ -34,24 +34,34 @@ static bool vsock_has_data(struct sock *sk, struct sk_psock *psock) return vsock_sk_has_data(sk, psock); } -static bool vsock_msg_wait_data(struct sock *sk, struct sk_psock *psock, long timeo) +/* __vsock_recvmsg() doesn't wait in these states and knows what to return. */ +static bool vsock_rx_done(struct sock *sk) { - bool ret; - - DEFINE_WAIT_FUNC(wait, woken_wake_function); + return sk->sk_err || sk->sk_state != TCP_ESTABLISHED || + (sk->sk_shutdown & RCV_SHUTDOWN) || + (vsock_sk(sk)->peer_shutdown & SEND_SHUTDOWN); +} - if (sk->sk_shutdown & RCV_SHUTDOWN) - return true; +static int vsock_msg_wait_data(struct sock *sk, struct sk_psock *psock, long timeo) +{ + int ret = 0; - if (!timeo) - return false; + DEFINE_WAIT_FUNC(wait, woken_wake_function); add_wait_queue(sk_sleep(sk), &wait); sk_set_bit(SOCKWQ_ASYNC_WAITDATA, sk); - ret = vsock_has_data(sk, psock); - if (!ret) { - wait_woken(&wait, TASK_INTERRUPTIBLE, timeo); - ret = vsock_has_data(sk, psock); + while (!vsock_has_data(sk, psock) && !vsock_rx_done(sk)) { + if (!timeo) { + ret = -EAGAIN; + break; + } + if (signal_pending(current)) { + ret = sock_intr_errno(timeo); + break; + } + release_sock(sk); + timeo = wait_woken(&wait, TASK_INTERRUPTIBLE, timeo); + lock_sock(sk); } sk_clear_bit(SOCKWQ_ASYNC_WAITDATA, sk); remove_wait_queue(sk_sleep(sk), &wait); @@ -80,6 +90,9 @@ static int vsock_bpf_recvmsg(struct sock *sk, struct msghdr *msg, struct vsock_sock *vsk; int copied; + if (unlikely(!len || (flags & (MSG_OOB | MSG_ERRQUEUE)))) + return __vsock_recvmsg(sk, msg, len, flags); + psock = sk_psock_get(sk); if (unlikely(!psock)) return __vsock_recvmsg(sk, msg, len, flags); @@ -102,10 +115,9 @@ static int vsock_bpf_recvmsg(struct sock *sk, struct msghdr *msg, while (copied == 0) { long timeo = sock_rcvtimeo(sk, flags & MSG_DONTWAIT); - if (!vsock_msg_wait_data(sk, psock, timeo)) { - copied = -EAGAIN; + copied = vsock_msg_wait_data(sk, psock, timeo); + if (copied) break; - } if (sk_psock_queue_empty(psock)) { release_sock(sk); [...] > guest's virtio-vsock device. With the series applied they behave as on > a native socket, except for the reset case above, and the vsock > vmtest.sh single-VM tests and the BPF sockmap test_progs pass. None of these tests sleeps in vsock_msg_wait_data(). The sockmap tests call select() before recv() or pass MSG_DONTWAIT. vmtest.sh doesn't use sockmap. pw-bot: cr