From 98f28d8d6e5a5ed058dd37854c19e9b3bae72eff Mon Sep 17 00:00:00 2001 From: Laurence Rowe Date: Thu, 2 Apr 2026 13:49:18 -0700 Subject: [PATCH] vsock: avoid timeout for non-blocking accept() with empty backlog A common pattern in epoll network servers is to eagerly accept all pending connections from the non-blocking listening socket after epoll_wait indicates the socket is ready by calling accept in a loop until EAGAIN is returned indicating that the backlog is empty. Scheduling a timeout for a non-blocking accept with an empty backlog meant AF_VSOCK sockets used by epoll network servers incurred hundreds of microseconds of additional latency per accept loop compared to AF_INET or AF_UNIX sockets. Signed-off-by: Laurence Rowe Reviewed-by: Bobby Eshleman Reviewed-by: Stefano Garzarella Link: https://patch.msgid.link/20260402204918.130395-1-laurencerowe@gmail.com Signed-off-by: Jakub Kicinski --- net/vmw_vsock/af_vsock.c | 15 ++++++--------- 1 file changed, 6 insertions(+), 9 deletions(-) diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c index e4756604d50b9..b8794ea0f01e9 100644 --- a/net/vmw_vsock/af_vsock.c +++ b/net/vmw_vsock/af_vsock.c @@ -1864,10 +1864,10 @@ static int vsock_accept(struct socket *sock, struct socket *newsock, * created upon connection establishment. */ timeout = sock_rcvtimeo(listener, arg->flags & O_NONBLOCK); - prepare_to_wait(sk_sleep(listener), &wait, TASK_INTERRUPTIBLE); while ((connected = vsock_dequeue_accept(listener)) == NULL && - listener->sk_err == 0) { + listener->sk_err == 0 && timeout != 0) { + prepare_to_wait(sk_sleep(listener), &wait, TASK_INTERRUPTIBLE); release_sock(listener); timeout = schedule_timeout(timeout); finish_wait(sk_sleep(listener), &wait); @@ -1876,17 +1876,14 @@ static int vsock_accept(struct socket *sock, struct socket *newsock, if (signal_pending(current)) { err = sock_intr_errno(timeout); goto out; - } else if (timeout == 0) { - err = -EAGAIN; - goto out; } - - prepare_to_wait(sk_sleep(listener), &wait, TASK_INTERRUPTIBLE); } - finish_wait(sk_sleep(listener), &wait); - if (listener->sk_err) + if (listener->sk_err) { err = -listener->sk_err; + } else if (!connected) { + err = -EAGAIN; + } if (connected) { sk_acceptq_removed(listener); -- 2.47.3