erts: Guard against IN events in poll thread

If an IN event is triggered in the poll thread just
as migration happens to scheduler polling, we should
just ignore that event as the scheduler poll will
get the same event.

erts/emulator/sys/common/erl_check_io.c

@@ -2037,14 +2037,17 @@ erts_check_io(ErtsPollThread *psi, ErtsMonotonicTime timeout_time, int poll_only
 #endif
             {
                 ErtsPollEvents reactive_events;
+
+                if (state->flags & ERTS_EV_FLAG_SCHEDULER) {
+                    /*  We are in a poll thread and the fd is managed
+                        by a scheduler, we ignore the any IN events  */
+                    revents &= ~ERTS_POLL_EV_IN;
+                }
+
                 state->active_events &= ~revents;
 
                 reactive_events = state->active_events;
 
-                if (state->flags & ERTS_EV_FLAG_IN_SCHEDULER) {
-                    state->active_events |= ERTS_POLL_EV_IN;
-                }
-
                 /* Reactivate the poll op if there are still active events */
                 if (reactive_events) {
                     ErtsPollEvents new_events;