[PATCH] POLLRDHUP/EPOLLRDHUP handling for half-closed devices notifications

Implement the half-closed devices notifiation, by adding a new POLLRDHUP
(and its alias EPOLLRDHUP) bit to the existing poll/select sets.  Since the
existing POLLHUP handling, that does not report correctly half-closed
devices, was feared to be changed, this implementation leaves the current
POLLHUP reporting unchanged and simply add a new bit that is set in the few
places where it makes sense.  The same thing was discussed and conceptually
agreed quite some time ago:

http://lkml.org/lkml/2003/7/12/116

Since this new event bit is added to the existing Linux poll infrastruture,
even the existing poll/select system calls will be able to use it.  As far
as the existing POLLHUP handling, the patch leaves it as is.  The
pollrdhup-2.6.16.rc5-0.10.diff defines the POLLRDHUP for all the existing
archs and sets the bit in the six relevant files.  The other attached diff
is the simple change required to sys/epoll.h to add the EPOLLRDHUP
definition.

There is "a stupid program" to test POLLRDHUP delivery here:

 http://www.xmailserver.org/pollrdhup-test.c

It tests poll(2), but since the delivery is same epoll(2) will work equally.

Signed-off-by: Davide Libenzi <davidel@xmailserver.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Michael Kerrisk <mtk-manpages@gmx.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

net/bluetooth/af_bluetooth.c

diff --git a/net/bluetooth/af_bluetooth.c b/net/bluetooth/af_bluetooth.c
index fb031fe..469eda0 100644
--- a/net/bluetooth/af_bluetooth.c
+++ b/net/bluetooth/af_bluetooth.c
@@ -238,6 +238,9 @@
 	if (sk->sk_err || !skb_queue_empty(&sk->sk_error_queue))
 		mask |= POLLERR;
 
+	if (sk->sk_shutdown & RCV_SHUTDOWN)
+		mask |= POLLRDHUP;
+
 	if (sk->sk_shutdown == SHUTDOWN_MASK)
 		mask |= POLLHUP;
 

net/core/datagram.c

diff --git a/net/core/datagram.c b/net/core/datagram.c
index b8ce6bf..aecddcc 100644
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -500,6 +500,8 @@
 	/* exceptional events? */
 	if (sk->sk_err || !skb_queue_empty(&sk->sk_error_queue))
 		mask |= POLLERR;
+	if (sk->sk_shutdown & RCV_SHUTDOWN)
+		mask |= POLLRDHUP;
 	if (sk->sk_shutdown == SHUTDOWN_MASK)
 		mask |= POLLHUP;
 

net/dccp/proto.c

diff --git a/net/dccp/proto.c b/net/dccp/proto.c
index d4b293e..1ff7328b 100644
--- a/net/dccp/proto.c
+++ b/net/dccp/proto.c
@@ -350,7 +350,7 @@
 	if (sk->sk_shutdown == SHUTDOWN_MASK || sk->sk_state == DCCP_CLOSED)
 		mask |= POLLHUP;
 	if (sk->sk_shutdown & RCV_SHUTDOWN)
-		mask |= POLLIN | POLLRDNORM;
+		mask |= POLLIN | POLLRDNORM | POLLRDHUP;
 
 	/* Connected? */
 	if ((1 << sk->sk_state) & ~(DCCPF_REQUESTING | DCCPF_RESPOND)) {

net/ipv4/tcp.c

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 4b0272c..19ea5c0 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -365,7 +365,7 @@
 	if (sk->sk_shutdown == SHUTDOWN_MASK || sk->sk_state == TCP_CLOSE)
 		mask |= POLLHUP;
 	if (sk->sk_shutdown & RCV_SHUTDOWN)
-		mask |= POLLIN | POLLRDNORM;
+		mask |= POLLIN | POLLRDNORM | POLLRDHUP;
 
 	/* Connected? */
 	if ((1 << sk->sk_state) & ~(TCPF_SYN_SENT | TCPF_SYN_RECV)) {

net/sctp/socket.c

diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index 0ea947e..b6e4b89 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -4894,6 +4894,8 @@
 	/* Is there any exceptional events?  */
 	if (sk->sk_err || !skb_queue_empty(&sk->sk_error_queue))
 		mask |= POLLERR;
+	if (sk->sk_shutdown & RCV_SHUTDOWN)
+		mask |= POLLRDHUP;
 	if (sk->sk_shutdown == SHUTDOWN_MASK)
 		mask |= POLLHUP;
 

net/unix/af_unix.c

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 2b4cc2e..d901465 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -1878,6 +1878,8 @@
 		mask |= POLLERR;
 	if (sk->sk_shutdown == SHUTDOWN_MASK)
 		mask |= POLLHUP;
+	if (sk->sk_shutdown & RCV_SHUTDOWN)
+		mask |= POLLRDHUP;
 
 	/* readable? */
 	if (!skb_queue_empty(&sk->sk_receive_queue) ||