gh-133744: Fix multiprocessing interrupt test: add an event (#133746)

Add an event to synchronize the parent process with the child
process: wait until the child process starts sleeping.

(cherry picked from commit c2989b7)

Author: vstinner

Lib/test/_test_multiprocessing.py

@@ -511,6 +511,11 @@ def _test_process_mainthread_native_id(cls, q):
     def _sleep_some(cls):
         time.sleep(100)
 
+    @classmethod
+    def _sleep_some_event(cls, event):
+        event.set()
+        time.sleep(100)
+
     @classmethod
     def _test_sleep(cls, delay):
         time.sleep(delay)
@@ -519,7 +524,8 @@ def _kill_process(self, meth):
         if self.TYPE == 'threads':
             self.skipTest('test not appropriate for {}'.format(self.TYPE))
 
-        p = self.Process(target=self._sleep_some)
+        event = self.Event()
+        p = self.Process(target=self._sleep_some_event, args=(event,))
         p.daemon = True
         p.start()
 
@@ -537,8 +543,11 @@ def _kill_process(self, meth):
         self.assertTimingAlmostEqual(join.elapsed, 0.0)
         self.assertEqual(p.is_alive(), True)
 
-        # XXX maybe terminating too soon causes the problems on Gentoo...
-        time.sleep(1)
+        timeout = support.SHORT_TIMEOUT
+        if not event.wait(timeout):
+            p.terminate()
+            p.join()
+            self.fail(f"event not signaled in {timeout} seconds")
 
         meth(p)
 

Misc/NEWS.d/next/Tests/2025-05-09-14-54-48.gh-issue-133744.LCquu0.rst

@@ -0,0 +1,3 @@
+Fix multiprocessing interrupt test. Add an event to synchronize the parent
+process with the child process: wait until the child process starts
+sleeping. Patch by Victor Stinner.