/**
* 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* since the pollmask info is potentially out-of-date the moment this routine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;
}
