[glib] Reorder operations in _kqsub_cancel() to prevent races.

[Philip Withnall <pwithnall src gnome org>]

commit ab179184b883ad378a420223f378071821f0c8b9
Author: Martin Pieuchot <mpi openbsd org>
Date:   Wed Apr 11 17:58:07 2018 +0200

    Reorder operations in _kqsub_cancel() to prevent races.
    
    Removing the event and closing the related file descriptor must be
    done first to make sure the kqueue subsystem delete pending events.
    
    The timeout must be disarmed before freeing the directory dependency
    list otherwise it might populate it again.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=795193

 gio/kqueue/gkqueuefilemonitor.c | 28 ++++++++++++++--------------
 1 file changed, 14 insertions(+), 14 deletions(-)
---
diff --git a/gio/kqueue/gkqueuefilemonitor.c b/gio/kqueue/gkqueuefilemonitor.c
index deed8b1e1..d6fea41cf 100644
--- a/gio/kqueue/gkqueuefilemonitor.c
+++ b/gio/kqueue/gkqueuefilemonitor.c
@@ -373,28 +373,28 @@ _kqsub_cancel (kqueue_sub *sub)
 {
   struct kevent ev;
 
-  if (sub->deps)
+  /* Remove the event and close the file descriptor to automatically
+   * delete pending events. */
+  if (sub->fd != -1)
     {
-      dl_free (sub->deps);
-      sub->deps = NULL;
+      EV_SET (&ev, sub->fd, EVFILT_VNODE, EV_DELETE, NOTE_ALL, 0, sub);
+      if (kevent (kq_queue, &ev, 1, NULL, 0, NULL) == -1)
+        {
+          g_warning ("Unable to remove event for %s: %s", sub->filename, g_strerror (errno));
+          return FALSE;
+        }
+      close (sub->fd);
+      sub->fd = -1;
     }
 
   _km_remove (sub);
 
-  /* Only in the missing list?  We're done! */
-  if (sub->fd == -1)
-    return TRUE;
-
-  EV_SET (&ev, sub->fd, EVFILT_VNODE, EV_DELETE, NOTE_ALL, 0, sub);
-  if (kevent (kq_queue, &ev, 1, NULL, 0, NULL) == -1)
+  if (sub->deps)
     {
-      g_warning ("Unable to remove event for %s: %s", sub->filename, g_strerror (errno));
-      return FALSE;
+      dl_free (sub->deps);
+      sub->deps = NULL;
     }
 
-  close (sub->fd);
-  sub->fd = -1;
-
   return TRUE;
 }