Patch up race condition exposed in #478

DMOJ · Sep 17, 2019 · c267b56 · c267b56
1 parent 4cb878f
commit c267b56
Showing 1 changed file with 2 additions and 1 deletion.
diff --git a/dmoj/judge.py b/dmoj/judge.py
@@ -115,7 +115,8 @@ def process_submission(self, type, target, id, *args, **kwargs):
         self.current_submission_thread.daemon = True
         self.current_submission_thread.start()
 
-        if is_blocking:
+        # Submission may have been killed already, but block if it hasn't been.
+        if is_blocking and self.current_submission_thread is not None:
             self.current_submission_thread.join()
 
     def _custom_invocation(self, language, source, memory_limit, time_limit, input_data):