main loop: use msec-based timeout in glib_select_fill

The timeval-based timeout is not needed until we actually invoke select,
so compute it only then.  Also group the two calls that modify the
timeout, glib_select_fill and os_host_main_loop_wait.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>

main-loop.c

@@ -224,11 +224,11 @@ static int n_poll_fds;
 static int max_priority;
 
 static void glib_select_fill(int *max_fd, fd_set *rfds, fd_set *wfds,
-                             fd_set *xfds, struct timeval *tv)
+                             fd_set *xfds, int *cur_timeout)
 {
     GMainContext *context = g_main_context_default();
     int i;
-    int timeout = 0, cur_timeout;
+    int timeout = 0;
 
     g_main_context_prepare(context, &max_priority);
 
@@ -253,10 +253,8 @@ static void glib_select_fill(int *max_fd, fd_set *rfds, fd_set *wfds,
         }
     }
 
-    cur_timeout = (tv->tv_sec * 1000) + ((tv->tv_usec + 500) / 1000);
-    if (timeout >= 0 && timeout < cur_timeout) {
-        tv->tv_sec = timeout / 1000;
-        tv->tv_usec = (timeout % 1000) * 1000;
+    if (timeout >= 0 && timeout < *cur_timeout) {
+        *cur_timeout = timeout;
     }
 }
 
@@ -432,11 +430,6 @@ int main_loop_wait(int nonblocking)
         qemu_bh_update_timeout(&timeout);
     }
 
-    os_host_main_loop_wait(&timeout);
-
-    tv.tv_sec = timeout / 1000;
-    tv.tv_usec = (timeout % 1000) * 1000;
-
     /* poll any events */
     /* XXX: separate device handlers from system ones */
     nfds = -1;
@@ -448,7 +441,12 @@ int main_loop_wait(int nonblocking)
     slirp_select_fill(&nfds, &rfds, &wfds, &xfds);
 #endif
     qemu_iohandler_fill(&nfds, &rfds, &wfds, &xfds);
-    glib_select_fill(&nfds, &rfds, &wfds, &xfds, &tv);
+
+    glib_select_fill(&nfds, &rfds, &wfds, &xfds, &timeout);
+    os_host_main_loop_wait(&timeout);
+
+    tv.tv_sec = timeout / 1000;
+    tv.tv_usec = (timeout % 1000) * 1000;
 
     if (timeout > 0) {
         qemu_mutex_unlock_iothread();