af_unix: fix unix_dgram_poll() behavior for EPOLLOUT event
Alban Crequy reported a problem with connected dgram af_unix sockets and
provided a test program. epoll() would miss to send an EPOLLOUT event
when a thread unqueues a packet from the other peer, making its receive
queue not full.
This is because unix_dgram_poll() fails to call sock_poll_wait(file,
&unix_sk(other)->peer_wait, wait);
if the socket is not writeable at the time epoll_ctl(ADD) is called.
We must call sock_poll_wait(), regardless of 'writable' status, so that
epoll can be notified later of states changes.
Misc: avoids testing twice (sk->sk_shutdown & RCV_SHUTDOWN)
Reported-by: Alban Crequy <alban.crequy@collabora.co.uk>
Cc: Davide Libenzi <davidel@xmailserver.org>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Acked-by: Davide Libenzi <davidel@xmailserver.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index f33c595..e889875 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -2074,13 +2074,12 @@
if (sk->sk_err || !skb_queue_empty(&sk->sk_error_queue))
mask |= POLLERR;
if (sk->sk_shutdown & RCV_SHUTDOWN)
- mask |= POLLRDHUP;
+ mask |= POLLRDHUP | POLLIN | POLLRDNORM;
if (sk->sk_shutdown == SHUTDOWN_MASK)
mask |= POLLHUP;
/* readable? */
- if (!skb_queue_empty(&sk->sk_receive_queue) ||
- (sk->sk_shutdown & RCV_SHUTDOWN))
+ if (!skb_queue_empty(&sk->sk_receive_queue))
mask |= POLLIN | POLLRDNORM;
/* Connection-based need to check for termination and startup */
@@ -2092,20 +2091,15 @@
return mask;
}
- /* writable? */
writable = unix_writable(sk);
- if (writable) {
- other = unix_peer_get(sk);
- if (other) {
- if (unix_peer(other) != sk) {
- sock_poll_wait(file, &unix_sk(other)->peer_wait,
- wait);
- if (unix_recvq_full(other))
- writable = 0;
- }
-
- sock_put(other);
+ other = unix_peer_get(sk);
+ if (other) {
+ if (unix_peer(other) != sk) {
+ sock_poll_wait(file, &unix_sk(other)->peer_wait, wait);
+ if (unix_recvq_full(other))
+ writable = 0;
}
+ sock_put(other);
}
if (writable)