python · hanxinke · Apr 2, 2021 · Apr 2, 2021
diff --git a/Lib/test/test_threading.py b/Lib/test/test_threading.py
@@ -757,6 +757,18 @@ def test_shutdown_locks(self):
                # Daemon threads must never add it to _shutdown_locks.
                self.assertNotIn(tstate_lock, threading._shutdown_locks)

+    def test_leak_without_join(self):
+        # bpo-37788: Test that no continuous memory leak occurs when multiple
+        # subthreads which are not joined are started.
+        def noop(): pass
+        for i in range(10):
+            thread = threading.Thread(target=noop)
+            thread.start()
+            self.assertIn(thread._tstate_lock, threading._shutdown_locks)
+            while thread._tstate_lock.locked():
+                pass
+        self.assertLess(len(threading._shutdown_locks), 10)
+

 class ThreadJoinOnShutdown(BaseTestCase):


diff --git a/Lib/threading.py b/Lib/threading.py
@@ -896,6 +896,21 @@ def _bootstrap(self):
    def _set_ident(self):
        self._ident = get_ident()

+    def _discard_tstate_locks(self):
+        with _shutdown_locks_lock:
+            locks = list(_shutdown_locks)
+
+        if not locks:
+            return
+
+        for lock in locks:
+            if lock.locked():
+                continue
+            lock.acquire()
+            lock.release()
+            with _shutdown_locks_lock:
+                _shutdown_locks.discard(lock)
+
    def _set_tstate_lock(self):
        """
        Set a lock object which will be released by the interpreter when
@@ -964,7 +979,10 @@ def _bootstrap_inner(self):
                # the exception keeps the target alive past when we
                # assert that it's dead.
                #XXX self._exc_clear()
-                pass
+                # To prevent continuous leakage of tstate locks, try to discard at
+                # the end of each subthread.
+                if not self.daemon:
+                    self._discard_tstate_locks()
        finally:
            with _active_limbo_lock:
                try:

diff --git a/Misc/NEWS.d/next/Library/2021-04-02-11-56-50.bpo-37788.jbaJGP.rst b/Misc/NEWS.d/next/Library/2021-04-02-11-56-50.bpo-37788.jbaJGP.rst
@@ -0,0 +1 @@
+Add threading.Thread._discard_tstate_locks() method to check whether the lock of other subthreads can be deleted from the _shutdown_locks list when the subthread task ends and prevent continuous leakage of tstate locks.
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		Add threading.Thread._discard_tstate_locks() method to check whether the lock of other subthreads can be deleted from the _shutdown_locks list when the subthread task ends and prevent continuous leakage of tstate locks.