move cleanup after check that all events are handled

io/io_waituntil2.c

@@ -120,7 +120,19 @@ int64 io_waituntil2(int64 milliseconds) {
   struct pollfd* p;
 #endif
   long i,j,r;
-  if (first_deferred!=-1) {
+
+  /* if no interest in events has been registered, then return
+   * immediately */
+  if (!io_wanted_fds) return 0;
+
+  /* only actually wait if all previous events have been dequeued */
+  if (first_readable!=-1 || first_writeable!=-1) return 0;
+
+  /* There is a race if we get events on a socket, and someone calls
+   * io_close on the fd before they are handled. Those events are in a
+   * queue. So we try to detect if there are still queued events in
+   * io_close and then not actually close the descriptor but set
+   * e->closed so we can clean up the descriptor here. */
   while (first_deferred!=-1) {
     io_entry* e=iarray_get(&io_fds,first_deferred);
     if (e && e->closed) {
@@ -131,13 +143,6 @@ int64 io_waituntil2(int64 milliseconds) {
     } else
       first_deferred=-1;	// can't happen
   }
-  }
-  /* if no interest in events has been registered, then return
-   * immediately */
-  if (!io_wanted_fds) return 0;
-
-  /* only actually wait if all previous events have been dequeued */
-  if (first_readable!=-1 || first_writeable!=-1) return 0;
 
 #ifdef HAVE_EPOLL
   if (io_waitmode==EPOLL) {