/** * poll - read and possibly block on pollmask * @file: file structure associated with the socket * @sock: socket for which to calculate the poll bits * @wait: ??? * * 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* It appears that the usual socket locking mechanisms are not useful here * since the pollmask info is potentially out-of-date the moment this routine * exits.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: * * socket state flags set * ------------ --------- * unconnected no read flags * POLLOUT if port is not congested * * connecting POLLIN/POLLRDNORM if ACK/NACK in rx queue * no write flags * * connected POLLIN/POLLRDNORM if data in rx queue * POLLOUT if port is not congested * * disconnecting POLLIN/POLLRDNORM/POLLHUP * no write flags * * listening POLLIN if SYN in rx queue * no write flags * * ready POLLIN/POLLRDNORM if data in rx queue * [connectionless] POLLOUT (since port cannot be congested) * * IMPORTANT: The fact that a read or write operation is indicated does NOT * imply that the operation will succeed, merely that it should be performed * and will not block. */ static unsigned int poll(struct file *file, struct socket *sock, poll_table *wait) { struct sock *sk = sock->sk; u32 mask = 0; sock_poll_wait(file, sk_sleep(sk), wait); switch ((int)sock->state) { case SS_UNCONNECTED: if (!tipc_sk_port(sk)->congested) mask |= POLLOUT; break; case SS_READY: case SS_CONNECTED: if (!tipc_sk_port(sk)->congested) mask |= POLLOUT; /* fall thru' */ case SS_CONNECTING: case SS_LISTENING: if (!skb_queue_empty(&sk->sk_receive_queue)) mask |= (POLLIN | POLLRDNORM); break; case SS_DISCONNECTING: mask = (POLLIN | POLLRDNORM | POLLHUP); break; } return mask; }
/* * Wait for a DCCP event. * * Note that we don't need to lock the socket, as the upper poll layers * take care of normal races (between the test and the event) and we don't * go look at any of the socket buffers directly. */ unsigned int dccp_poll(struct file *file, struct socket *sock, poll_table *wait) { unsigned int mask; struct sock *sk = sock->sk; sock_poll_wait(file, sk_sleep(sk), wait); if (sk->sk_state == DCCP_LISTEN) return inet_csk_listen_poll(sk); /* Socket is not locked. We are protected from async events by poll logic and correct handling of state changes made by another threads is impossible in any case. */ mask = 0; if (sk->sk_err) mask = POLLERR; if (sk->sk_shutdown == SHUTDOWN_MASK || sk->sk_state == DCCP_CLOSED) mask |= POLLHUP; if (sk->sk_shutdown & RCV_SHUTDOWN) mask |= POLLIN | POLLRDNORM | POLLRDHUP; /* Connected? */ if ((1 << sk->sk_state) & ~(DCCPF_REQUESTING | DCCPF_RESPOND)) { if (atomic_read(&sk->sk_rmem_alloc) > 0) mask |= POLLIN | POLLRDNORM; if (!(sk->sk_shutdown & SEND_SHUTDOWN)) { if (sk_stream_is_writeable(sk)) { mask |= POLLOUT | POLLWRNORM; } else { /* send SIGIO later */ set_bit(SOCK_ASYNC_NOSPACE, &sk->sk_socket->flags); set_bit(SOCK_NOSPACE, &sk->sk_socket->flags); /* Race breaker. If space is freed after * wspace test but before the flags are set, * IO signal will be lost. */ if (sk_stream_is_writeable(sk)) mask |= POLLOUT | POLLWRNORM; } } } return mask; }
unsigned int dccp_poll(struct file *file, struct socket *sock, poll_table *wait) { unsigned int mask; struct sock *sk = sock->sk; sock_poll_wait(file, sk->sk_sleep, wait); if (sk->sk_state == DCCP_LISTEN) return inet_csk_listen_poll(sk); mask = 0; if (sk->sk_err) mask = POLLERR; if (sk->sk_shutdown == SHUTDOWN_MASK || sk->sk_state == DCCP_CLOSED) mask |= POLLHUP; if (sk->sk_shutdown & RCV_SHUTDOWN) mask |= POLLIN | POLLRDNORM | POLLRDHUP; if ((1 << sk->sk_state) & ~(DCCPF_REQUESTING | DCCPF_RESPOND)) { if (atomic_read(&sk->sk_rmem_alloc) > 0) mask |= POLLIN | POLLRDNORM; if (!(sk->sk_shutdown & SEND_SHUTDOWN)) { if (sk_stream_wspace(sk) >= sk_stream_min_wspace(sk)) { mask |= POLLOUT | POLLWRNORM; } else { set_bit(SOCK_ASYNC_NOSPACE, &sk->sk_socket->flags); set_bit(SOCK_NOSPACE, &sk->sk_socket->flags); if (sk_stream_wspace(sk) >= sk_stream_min_wspace(sk)) mask |= POLLOUT | POLLWRNORM; } } } return mask; }
/* * permit an RxRPC socket to be polled */ static __poll_t rxrpc_poll(struct file *file, struct socket *sock, poll_table *wait) { struct sock *sk = sock->sk; struct rxrpc_sock *rx = rxrpc_sk(sk); __poll_t mask; sock_poll_wait(file, sock, wait); mask = 0; /* the socket is readable if there are any messages waiting on the Rx * queue */ if (!list_empty(&rx->recvmsg_q)) mask |= EPOLLIN | EPOLLRDNORM; /* the socket is writable if there is space to add new data to the * socket; there is no guarantee that any particular call in progress * on the socket may have space in the Tx ACK window */ if (rxrpc_writable(sk)) mask |= EPOLLOUT | EPOLLWRNORM; return mask; }