Do not rely on is_alive

salt/utils/process.py

@@ -1169,13 +1169,17 @@ def add(self, proc):
 
     def cleanup(self):
         with self.lock:
-            for proc in self.processes:
-                if proc.is_alive():
-                    continue
-                proc.join()
-                # Only processes have a close method, threads do not.
-                if hasattr(proc, "close"):
+            for proc in self.processes[:]:
+                proc.join(0.01)
+                if hasattr(proc, "exitcode"):
+                    # Only processes have exitcode and a close method, threads
+                    # do not.
+                    if proc.exitcode is None:
+                        continue
                     proc.close()
+                else:
+                    if proc.is_alive():
+                        continue
                 self.processes.remove(proc)
                 self.count -= 1
                 log.debug("Subprocess %s cleaned up", proc.name)

tests/pytests/functional/utils/test_process.py

@@ -58,7 +58,10 @@ def target():
 
     process = salt.utils.process.SignalHandlingProcess(target=target)
     process.start()
+
     process_list.add(process)
+    time.sleep(0.3)
+
     num = _get_num_fds(pid)
     assert num == before_num + 2
     start = time.time()