From 33ba29de38edcc27c00cd51c1f583efc35530c1c Mon Sep 17 00:00:00 2001
From: hanxinke <hanxinke@huawei.com>
Date: Fri, 2 Apr 2021 18:07:50 -0400
Subject: [PATCH 1/2] bpo-37788: Fix continuous memory leak occurs when
 multiple subthreads which are not joined are started.

---
 Lib/test/test_threading.py | 12 ++++++++++++
 Lib/threading.py           | 20 +++++++++++++++++++-
 2 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/Lib/test/test_threading.py b/Lib/test/test_threading.py
index 36d9fbb162e215..c3717e544bdfaa 100644
--- 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
index b961456fb792a2..71fdc3fe64d9fd 100644
--- 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:

From 9a45081a413d4a2552e5ee4608b727461b390b16 Mon Sep 17 00:00:00 2001
From: "blurb-it[bot]" <43283697+blurb-it[bot]@users.noreply.github.com>
Date: Fri, 2 Apr 2021 11:56:51 +0000
Subject: [PATCH 2/2] =?UTF-8?q?=F0=9F=93=9C=F0=9F=A4=96=20Added=20by=20blu?=
 =?UTF-8?q?rb=5Fit.?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .../NEWS.d/next/Library/2021-04-02-11-56-50.bpo-37788.jbaJGP.rst | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 Misc/NEWS.d/next/Library/2021-04-02-11-56-50.bpo-37788.jbaJGP.rst

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
new file mode 100644
index 00000000000000..98a184d4d67be9
--- /dev/null
+++ 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.
\ No newline at end of file