[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>

fs/eventpoll.c

@@ -599,7 +599,7 @@ sys_epoll_ctl(int epfd, int op, int fd, struct epoll_event __user *event)
 	switch (op) {
 	case EPOLL_CTL_ADD:
 		if (!epi) {
-			epds.events |= POLLERR | POLLHUP;
+			epds.events |= POLLERR | POLLHUP | POLLRDHUP;
 
 			error = ep_insert(ep, &epds, tfile, fd);
 		} else
@@ -613,7 +613,7 @@ sys_epoll_ctl(int epfd, int op, int fd, struct epoll_event __user *event)
 		break;
 	case EPOLL_CTL_MOD:
 		if (epi) {
-			epds.events |= POLLERR | POLLHUP;
+			epds.events |= POLLERR | POLLHUP | POLLRDHUP;
 			error = ep_modify(ep, epi, &epds);
 		} else
 			error = -ENOENT;

include/asm-alpha/poll.h

@@ -13,6 +13,8 @@
 #define POLLWRBAND	(1 << 9)
 #define POLLMSG		(1 << 10)
 #define POLLREMOVE	(1 << 11)
+#define POLLRDHUP       (1 << 12)
+
 
 struct pollfd {
 	int fd;

include/asm-arm/poll.h

@@ -16,6 +16,7 @@
 #define POLLWRBAND	0x0200
 #define POLLMSG		0x0400
 #define POLLREMOVE	0x1000
+#define POLLRDHUP       0x2000
 
 struct pollfd {
 	int fd;

include/asm-arm26/poll.h

@@ -15,6 +15,7 @@
 #define POLLWRNORM	0x0100
 #define POLLWRBAND	0x0200
 #define POLLMSG		0x0400
+#define POLLRDHUP       0x2000
 
 struct pollfd {
 	int fd;

include/asm-cris/poll.h

@@ -15,6 +15,7 @@
 #define POLLWRBAND	512
 #define POLLMSG		1024
 #define POLLREMOVE	4096
+#define POLLRDHUP       8192
 
 struct pollfd {
 	int fd;

include/asm-frv/poll.h

@@ -12,6 +12,7 @@
 #define POLLRDBAND	128
 #define POLLWRBAND	256
 #define POLLMSG		0x0400
+#define POLLRDHUP       0x2000
 
 struct pollfd {
 	int fd;

include/asm-h8300/poll.h

@@ -12,6 +12,7 @@
 #define POLLRDBAND	128
 #define POLLWRBAND	256
 #define POLLMSG		0x0400
+#define POLLRDHUP       0x2000
 
 struct pollfd {
 	int fd;

include/asm-i386/poll.h

@@ -16,6 +16,7 @@
 #define POLLWRBAND	0x0200
 #define POLLMSG		0x0400
 #define POLLREMOVE	0x1000
+#define POLLRDHUP       0x2000
 
 struct pollfd {
 	int fd;

include/asm-ia64/poll.h

@@ -21,6 +21,7 @@
 #define POLLWRBAND	0x0200
 #define POLLMSG		0x0400
 #define POLLREMOVE	0x1000
+#define POLLRDHUP       0x2000
 
 struct pollfd {
 	int fd;

include/asm-m32r/poll.h

@@ -21,6 +21,7 @@
 #define POLLWRBAND	0x0200
 #define POLLMSG		0x0400
 #define POLLREMOVE	0x1000
+#define POLLRDHUP       0x2000
 
 struct pollfd {
 	int fd;

include/asm-m68k/poll.h

@@ -13,6 +13,7 @@
 #define POLLWRBAND	256
 #define POLLMSG		0x0400
 #define POLLREMOVE	0x1000
+#define POLLRDHUP       0x2000
 
 struct pollfd {
 	int fd;

include/asm-mips/poll.h

@@ -17,6 +17,7 @@
 /* These seem to be more or less nonstandard ...  */
 #define POLLMSG		0x0400
 #define POLLREMOVE	0x1000
+#define POLLRDHUP       0x2000
 
 struct pollfd {
 	int fd;

include/asm-parisc/poll.h

@@ -16,6 +16,7 @@
 #define POLLWRBAND	0x0200
 #define POLLMSG		0x0400
 #define POLLREMOVE	0x1000
+#define POLLRDHUP       0x2000
 
 struct pollfd {
 	int fd;

include/asm-powerpc/poll.h

@@ -13,6 +13,7 @@
 #define POLLWRBAND	0x0200
 #define POLLMSG		0x0400
 #define POLLREMOVE	0x1000
+#define POLLRDHUP       0x2000
 
 struct pollfd {
 	int fd;

include/asm-s390/poll.h

@@ -24,6 +24,7 @@
 #define POLLWRBAND	0x0200
 #define POLLMSG		0x0400
 #define POLLREMOVE	0x1000
+#define POLLRDHUP       0x2000
 
 struct pollfd {
 	int fd;

include/asm-sh/poll.h

@@ -16,6 +16,7 @@
 #define POLLWRBAND	0x0200
 #define POLLMSG		0x0400
 #define POLLREMOVE	0x1000
+#define POLLRDHUP       0x2000
 
 struct pollfd {
 	int fd;

include/asm-sh64/poll.h

@@ -26,6 +26,7 @@
 #define POLLWRNORM	0x0100
 #define POLLWRBAND	0x0200
 #define POLLMSG		0x0400
+#define POLLRDHUP       0x2000
 
 struct pollfd {
 	int fd;

include/asm-sparc/poll.h

@@ -13,6 +13,7 @@
 #define POLLWRBAND	256
 #define POLLMSG		512
 #define POLLREMOVE	1024
+#define POLLRDHUP       2048
 
 struct pollfd {
 	int fd;

include/asm-sparc64/poll.h

@@ -13,6 +13,7 @@
 #define POLLWRBAND	256
 #define POLLMSG		512
 #define POLLREMOVE	1024
+#define POLLRDHUP       2048
 
 struct pollfd {
 	int fd;

include/asm-v850/poll.h

@@ -13,6 +13,7 @@
 #define POLLWRBAND	0x0100
 #define POLLMSG		0x0400
 #define POLLREMOVE	0x1000
+#define POLLRDHUP       0x2000
 
 struct pollfd {
 	int fd;