pythongh-126434: What should be done if sys.exit() is called from a s…

…ignal handler (on a non-main thread)?

Lib/signal.py

@@ -81,6 +81,8 @@ def stop_signal_thread():
     global _signal_thread, _signal_queue
     if _signal_thread is not None:
         _signal_queue.put('STOP_SIGNAL_HANDLER')
+        _signal_thread.join()
+        _signal_thread = None
 
 def _signal_queue_handler():
     try:
@@ -98,12 +100,15 @@ def _signal_queue_handler():
                     _log_missing_signal_handler(signo)
             except Exception:
                 traceback.print_exc()
-                pass
+    except SystemExit:
+        pass # TODO: what should be done in the event of a handler calling `sys.exit()`?
     except:
-        pass
+        traceback.print_exc()
+        # import _thread
+        # _thread.interrupt_main()
+        # print(dir(threading.main_thread()))
     finally:
-        global _signal_thread
-        _signal_thread = None
+        pass
 
 # Similar to functools.wraps(), but only assign __doc__.
 # __module__ should be preserved,
@@ -132,6 +137,8 @@ def signal(signalnum, handler, use_dedicated_thread=True):
     else:
         if signal_int in _signo_to_handler:
             del _signo_to_handler[signal_int]
+        if 0 == len(_signo_to_handler):
+            stop_signal_thread()
         handler = _signal.signal(signal_int, _enum_to_int(handler))
         return old_handler or _int_to_enum(handler, Handlers)
 

Lib/test/support/threading_helper.py

@@ -5,6 +5,7 @@
 import threading
 import time
 import unittest
+import signal
 
 from test import support
 
@@ -28,6 +29,8 @@ def threading_setup():
 def threading_cleanup(*original_values):
     orig_count, orig_ndangling = original_values
 
+    signal.stop_signal_thread()
+
     timeout = 1.0
     for _ in support.sleeping_retry(timeout, error=False):
         # Copy the thread list to get a consistent output. threading._dangling

Lib/test/test_asyncio/test_unix_events.py

@@ -34,6 +34,7 @@
 
 def tearDownModule():
     asyncio.set_event_loop_policy(None)
+    signal.stop_signal_thread()
 
 
 MOCK_ANY = mock.ANY

bug.py

@@ -3,6 +3,7 @@
 import threading
 import time
 import multiprocessing
+import sys
 
 def sigint_self():
     time.sleep(1)
@@ -18,24 +19,27 @@ def run_signal_handler_dedicated_thread():
     event = multiprocessing.Event()
     def sigint_handler(_signo, _stack_frame):
         try:
-            x = 1 / 0
             print(f'{threading.current_thread().name}: sigint_handler is setting event')
-            event.set()
+            #event.set()
+            sys.exit()
         finally:
             print(f'{threading.current_thread().name}: sigint_handler is done')
 
     def sigterm_handler(_signo, _stack_frame):
         print(f'{threading.current_thread().name}: sigterm_handler is running')
         pass
 
-    signal.signal(signal.SIGTERM, sigterm_handler)
-    signal.signal(signal.SIGINT, sigint_handler)
+    signal.signal(signal.SIGINT, sigint_handler, True)
 
     threading.Thread(target=sigint_self, daemon=True).start()
     threading.Thread(target=sigkill_self, daemon=True).start() # Used for debugging only.
 
     print(f'{threading.current_thread().name}: Waiting on event. PID = {os.getpid()}')
-    event.wait()
+    while True:
+        if event.is_set():
+            break
+        else:
+            time.sleep(0.1)
     print(f'{threading.current_thread().name}: Waiting is done')
 
 if __name__ == '__main__':