From c0a2e2161d7c2c48aa3409401d59531f3714ff0c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?R=C3=A9mi=20Lapeyre?= <remi.lapeyre@lenstra.fr>
Date: Fri, 5 Jun 2020 15:48:16 +0200
Subject: [PATCH] Add multiprocessing.Lock.locked()

---
 Doc/library/multiprocessing.rst                             | 6 ++++++
 Lib/multiprocessing/synchronize.py                          | 3 +++
 Lib/test/_test_multiprocessing.py                           | 2 ++
 .../next/Library/2020-06-05-15-47-43.bpo-40872.hW9afp.rst   | 2 ++
 4 files changed, 13 insertions(+)
 create mode 100644 Misc/NEWS.d/next/Library/2020-06-05-15-47-43.bpo-40872.hW9afp.rst

diff --git a/Doc/library/multiprocessing.rst b/Doc/library/multiprocessing.rst
index 08258a65a89dc35..d92a359fbad69ac 100644
--- a/Doc/library/multiprocessing.rst
+++ b/Doc/library/multiprocessing.rst
@@ -1301,6 +1301,12 @@ object -- see :ref:`multiprocessing-managers`.
       Behavior is the same as in :meth:`threading.Lock.release` except that
       when invoked on an unlocked lock, a :exc:`ValueError` is raised.
 
+   .. method:: locked()
+
+      Return true if the lock is acquired.
+
+      .. versionadded:: 3.10
+
 
 .. class:: RLock()
 
diff --git a/Lib/multiprocessing/synchronize.py b/Lib/multiprocessing/synchronize.py
index 4fcbefc8bbefd33..e811d42a86f1976 100644
--- a/Lib/multiprocessing/synchronize.py
+++ b/Lib/multiprocessing/synchronize.py
@@ -161,6 +161,9 @@ class Lock(SemLock):
     def __init__(self, *, ctx):
         SemLock.__init__(self, SEMAPHORE, 1, 1, ctx=ctx)
 
+    def locked(self):
+        return self._semlock._is_zero()
+
     def __repr__(self):
         try:
             if self._semlock._is_mine():
diff --git a/Lib/test/_test_multiprocessing.py b/Lib/test/_test_multiprocessing.py
index d01a6680e409cb4..fb1f33ff376eb76 100644
--- a/Lib/test/_test_multiprocessing.py
+++ b/Lib/test/_test_multiprocessing.py
@@ -1230,8 +1230,10 @@ class _TestLock(BaseTestCase):
     def test_lock(self):
         lock = self.Lock()
         self.assertEqual(lock.acquire(), True)
+        self.assertTrue(lock.locked())
         self.assertEqual(lock.acquire(False), False)
         self.assertEqual(lock.release(), None)
+        self.assertFalse(lock.locked())
         self.assertRaises((ValueError, threading.ThreadError), lock.release)
 
     def test_rlock(self):
diff --git a/Misc/NEWS.d/next/Library/2020-06-05-15-47-43.bpo-40872.hW9afp.rst b/Misc/NEWS.d/next/Library/2020-06-05-15-47-43.bpo-40872.hW9afp.rst
new file mode 100644
index 000000000000000..0b2c3402484f8b0
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2020-06-05-15-47-43.bpo-40872.hW9afp.rst
@@ -0,0 +1,2 @@
+:class:`multiprocessing.Lock` now has a `locked()` method that returns
+whether the lock is currently held. Patch contributed by Rémi Lapeyre.