diff options
| -rw-r--r-- | Lib/test/test_threading.py | 7 | ||||
| -rw-r--r-- | Lib/threading.py | 19 | ||||
| -rw-r--r-- | Misc/NEWS.d/next/Library/2021-05-13-19-07-28.bpo-37788.adeFcf.rst | 1 |
3 files changed, 26 insertions, 1 deletions
diff --git a/Lib/test/test_threading.py b/Lib/test/test_threading.py index 546773e..08c0ccd 100644 --- a/Lib/test/test_threading.py +++ b/Lib/test/test_threading.py @@ -907,6 +907,13 @@ class ThreadTests(BaseTestCase): thread.join() self.assertTrue(target.ran) + def test_leak_without_join(self): + # bpo-37788: Test that a thread which is not joined explicitly + # does not leak. Test written for reference leak checks. + def noop(): pass + with threading_helper.wait_threads_exit(): + threading.Thread(target=noop).start() + # Thread.join() is not called class ThreadJoinOnShutdown(BaseTestCase): diff --git a/Lib/threading.py b/Lib/threading.py index fb70abd..6c3d49c 100644 --- a/Lib/threading.py +++ b/Lib/threading.py @@ -780,12 +780,27 @@ _active_limbo_lock = _allocate_lock() _active = {} # maps thread id to Thread object _limbo = {} _dangling = WeakSet() + # Set of Thread._tstate_lock locks of non-daemon threads used by _shutdown() # to wait until all Python thread states get deleted: # see Thread._set_tstate_lock(). _shutdown_locks_lock = _allocate_lock() _shutdown_locks = set() +def _maintain_shutdown_locks(): + """ + Drop any shutdown locks that don't correspond to running threads anymore. + + Calling this from time to time avoids an ever-growing _shutdown_locks + set when Thread objects are not joined explicitly. See bpo-37788. + + This must be called with _shutdown_locks_lock acquired. + """ + # If a lock was released, the corresponding thread has exited + to_remove = [lock for lock in _shutdown_locks if not lock.locked()] + _shutdown_locks.difference_update(to_remove) + + # Main class for threads class Thread: @@ -968,6 +983,7 @@ class Thread: if not self.daemon: with _shutdown_locks_lock: + _maintain_shutdown_locks() _shutdown_locks.add(self._tstate_lock) def _bootstrap_inner(self): @@ -1023,7 +1039,8 @@ class Thread: self._tstate_lock = None if not self.daemon: with _shutdown_locks_lock: - _shutdown_locks.discard(lock) + # Remove our lock and other released locks from _shutdown_locks + _maintain_shutdown_locks() def _delete(self): "Remove current thread from the dict of currently running threads." diff --git a/Misc/NEWS.d/next/Library/2021-05-13-19-07-28.bpo-37788.adeFcf.rst b/Misc/NEWS.d/next/Library/2021-05-13-19-07-28.bpo-37788.adeFcf.rst new file mode 100644 index 0000000..0c33923 --- /dev/null +++ b/Misc/NEWS.d/next/Library/2021-05-13-19-07-28.bpo-37788.adeFcf.rst @@ -0,0 +1 @@ +Fix a reference leak when a Thread object is never joined. |