[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>

1 files changed, 2 insertions, 2 deletions

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 1c2b16fda13a..a0f682cdd03e 100644
--- a/fs/eventpoll.c
+++ b/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;