From 9b674e82b73a61844967b32e1b4ecaf8eb9d1805 Mon Sep 17 00:00:00 2001 From: Allan Stephens Date: Wed, 26 Mar 2008 16:48:21 -0700 Subject: [PATCH] [TIPC]: Cosmetic cleanup of TIPC polling logic This patch eliminates an unnecessary poll-related routine by merging it into TIPC's main polling routine, and updates the comments associated with this code. Signed-off-by: Allan Stephens Signed-off-by: David S. Miller --- net/tipc/socket.c | 78 ++++++++++++++++++++++------------------------- 1 file changed, 36 insertions(+), 42 deletions(-) diff --git a/net/tipc/socket.c b/net/tipc/socket.c index ae45df060e3a..1b5fb6103ded 100644 --- a/net/tipc/socket.c +++ b/net/tipc/socket.c @@ -101,44 +101,6 @@ static void sock_unlock(struct tipc_sock* tsock) spin_unlock_bh(tsock->p->lock); } -/** - * pollmask - determine the current set of poll() events for a socket - * @sock: socket structure - * - * TIPC sets the returned events as follows: - * a) POLLRDNORM and POLLIN are set if the socket's receive queue is non-empty - * or if a connection-oriented socket is does not have an active connection - * (i.e. a read operation will not block). - * b) POLLOUT is set except when a socket's connection has been terminated - * (i.e. a write operation will not block). - * c) POLLHUP is set when a socket's connection has been terminated. - * - * IMPORTANT: The fact that a read or write operation will not block does NOT - * imply that the operation will succeed! - * - * Returns pollmask value - */ - -static u32 pollmask(struct socket *sock) -{ - u32 mask; - - if ((skb_queue_len(&sock->sk->sk_receive_queue) != 0) || - (sock->state == SS_UNCONNECTED) || - (sock->state == SS_DISCONNECTING)) - mask = (POLLRDNORM | POLLIN); - else - mask = 0; - - if (sock->state == SS_DISCONNECTING) - mask |= POLLHUP; - else - mask |= POLLOUT; - - return mask; -} - - /** * advance_queue - discard first buffer in queue * @tsock: TIPC socket @@ -390,15 +352,47 @@ static int get_name(struct socket *sock, struct sockaddr *uaddr, * @sock: socket for which to calculate the poll bits * @wait: ??? * - * Returns the pollmask + * Returns pollmask value + * + * COMMENTARY: + * It appears that the usual socket locking mechanisms are not useful here + * since the pollmask info is potentially out-of-date the moment this routine + * exits. TCP and other protocols seem to rely on higher level poll routines + * to handle any preventable race conditions, so TIPC will do the same ... + * + * TIPC sets the returned events as follows: + * a) POLLRDNORM and POLLIN are set if the socket's receive queue is non-empty + * or if a connection-oriented socket is does not have an active connection + * (i.e. a read operation will not block). + * b) POLLOUT is set except when a socket's connection has been terminated + * (i.e. a write operation will not block). + * c) POLLHUP is set when a socket's connection has been terminated. + * + * IMPORTANT: The fact that a read or write operation will not block does NOT + * imply that the operation will succeed! */ static unsigned int poll(struct file *file, struct socket *sock, poll_table *wait) { - poll_wait(file, sock->sk->sk_sleep, wait); - /* NEED LOCK HERE? */ - return pollmask(sock); + struct sock *sk = sock->sk; + u32 mask; + + poll_wait(file, sk->sk_sleep, wait); + + if (!skb_queue_empty(&sk->sk_receive_queue) || + (sock->state == SS_UNCONNECTED) || + (sock->state == SS_DISCONNECTING)) + mask = (POLLRDNORM | POLLIN); + else + mask = 0; + + if (sock->state == SS_DISCONNECTING) + mask |= POLLHUP; + else + mask |= POLLOUT; + + return mask; } /** -- 2.20.1