From 6398e23cdb1d807132c1d3d007d6b1ec87b511af Mon Sep 17 00:00:00 2001 From: Ying Xue Date: Fri, 17 Jan 2014 09:50:04 +0800 Subject: [PATCH] tipc: standardize accept routine Comparing the behaviour of how to wait for events in TIPC accept() with other stacks, the TIPC implementation might be perceived as different, and sometimes even incorrect. As sk_sleep() and sk->sk_receive_queue variables associated with socket are not protected by socket lock, the process of calling accept() may be woken up improperly or sometimes cannot be woken up at all. After standardizing it with inet_csk_wait_for_connect routine, we can get benefits including: avoiding 'thundering herd' phenomenon, adding a timeout mechanism for accept(), coping with a pending signal, and having sk_sleep() and sk->sk_receive_queue being always protected within socket lock scope and so on. Signed-off-by: Ying Xue Reviewed-by: Jon Maloy Signed-off-by: David S. Miller --- net/tipc/socket.c | 54 +++++++++++++++++++++++++++++++++++------------ 1 file changed, 41 insertions(+), 13 deletions(-) diff --git a/net/tipc/socket.c b/net/tipc/socket.c index b2ae25ae3038..008f6fdf95c3 100644 --- a/net/tipc/socket.c +++ b/net/tipc/socket.c @@ -1566,6 +1566,42 @@ static int listen(struct socket *sock, int len) return res; } +static int tipc_wait_for_accept(struct socket *sock, long timeo) +{ + struct sock *sk = sock->sk; + DEFINE_WAIT(wait); + int err; + + /* True wake-one mechanism for incoming connections: only + * one process gets woken up, not the 'whole herd'. + * Since we do not 'race & poll' for established sockets + * anymore, the common case will execute the loop only once. + */ + for (;;) { + prepare_to_wait_exclusive(sk_sleep(sk), &wait, + TASK_INTERRUPTIBLE); + if (skb_queue_empty(&sk->sk_receive_queue)) { + release_sock(sk); + timeo = schedule_timeout(timeo); + lock_sock(sk); + } + err = 0; + if (!skb_queue_empty(&sk->sk_receive_queue)) + break; + err = -EINVAL; + if (sock->state != SS_LISTENING) + break; + err = sock_intr_errno(timeo); + if (signal_pending(current)) + break; + err = -EAGAIN; + if (!timeo) + break; + } + finish_wait(sk_sleep(sk), &wait); + return err; +} + /** * accept - wait for connection request * @sock: listening socket @@ -1582,7 +1618,7 @@ static int accept(struct socket *sock, struct socket *new_sock, int flags) struct tipc_port *new_tport; struct tipc_msg *msg; u32 new_ref; - + long timeo; int res; lock_sock(sk); @@ -1592,18 +1628,10 @@ static int accept(struct socket *sock, struct socket *new_sock, int flags) goto exit; } - while (skb_queue_empty(&sk->sk_receive_queue)) { - if (flags & O_NONBLOCK) { - res = -EWOULDBLOCK; - goto exit; - } - release_sock(sk); - res = wait_event_interruptible(*sk_sleep(sk), - (!skb_queue_empty(&sk->sk_receive_queue))); - lock_sock(sk); - if (res) - goto exit; - } + timeo = sock_rcvtimeo(sk, flags & O_NONBLOCK); + res = tipc_wait_for_accept(sock, timeo); + if (res) + goto exit; buf = skb_peek(&sk->sk_receive_queue); -- GitLab