main-loop: narrow win32 pollfds_fill() event bitmasks

pollfds_fill() and pollfds_poll() translate GPollFD to rfds/wfds/xfds
for sockets on win32.  select(2) is the underlying system call which is
used to monitor sockets for activity.

Currently file descriptors that monitor G_IO_ERR will be included in
both rfds and wfds.  As a result, select(2) will report writability on
file descriptors where we only really wanted to monitor readability
(with errors).

slirp_pollfds_poll() hit this issue: UDP sockets are blocking sockets so
we hang in sorecvfrom() when G_IO_ERR is set due to the socket being
writable (we only wanted to check for readability).

This patch fixes the slirp_pollfds_poll() hang.
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>
Message-id: 1368718561-7816-2-git-send-email-stefanha@redhat.com
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

main-loop.c

@@ -333,11 +333,11 @@ static int pollfds_fill(GArray *pollfds, fd_set *rfds, fd_set *wfds,
         GPollFD *pfd = &g_array_index(pollfds, GPollFD, i);
         int fd = pfd->fd;
         int events = pfd->events;
-        if (events & (G_IO_IN | G_IO_HUP | G_IO_ERR)) {
+        if (events & G_IO_IN) {
             FD_SET(fd, rfds);
             nfds = MAX(nfds, fd);
         }
-        if (events & (G_IO_OUT | G_IO_ERR)) {
+        if (events & G_IO_OUT) {
             FD_SET(fd, wfds);
             nfds = MAX(nfds, fd);
         }
@@ -360,10 +360,10 @@ static void pollfds_poll(GArray *pollfds, int nfds, fd_set *rfds,
         int revents = 0;
 
         if (FD_ISSET(fd, rfds)) {
-            revents |= G_IO_IN | G_IO_HUP | G_IO_ERR;
+            revents |= G_IO_IN;
         }
         if (FD_ISSET(fd, wfds)) {
-            revents |= G_IO_OUT | G_IO_ERR;
+            revents |= G_IO_OUT;
         }
         if (FD_ISSET(fd, xfds)) {
             revents |= G_IO_PRI;