From 339467eb8564d5f28b64ff817f29d59fc557be87 Mon Sep 17 00:00:00 2001
From: Victor Stinner <vstinner@python.org>
Date: Wed, 20 Sep 2023 18:25:45 +0200
Subject: [PATCH] gh-109593: ResourceTracker.ensure_running() calls finalizers

multiprocessing: Reduce the risk of reentrant calls to
ResourceTracker.ensure_running() by running explicitly all finalizers
before acquiring the ResourceTracker lock.
---
 Lib/multiprocessing/resource_tracker.py                    | 7 +++++++
 .../Library/2023-09-20-18-28-12.gh-issue-109593.VVWJDC.rst | 3 +++
 2 files changed, 10 insertions(+)
 create mode 100644 Misc/NEWS.d/next/Library/2023-09-20-18-28-12.gh-issue-109593.VVWJDC.rst

diff --git a/Lib/multiprocessing/resource_tracker.py b/Lib/multiprocessing/resource_tracker.py
index 3783c1ffc6e4a92..dbd10aa74d2a6e5 100644
--- a/Lib/multiprocessing/resource_tracker.py
+++ b/Lib/multiprocessing/resource_tracker.py
@@ -80,6 +80,13 @@ def ensure_running(self):
 
         This can be run from any process.  Usually a child process will use
         the resource created by its parent.'''
+
+        # gh-109593: Reduce the risk of reentrant calls to ensure_running() by
+        # running explicitly all finalizers. Otherwise, finalizers like
+        # SemLock._cleanup() can make indirectly a reentrant call to
+        # ensure_running().
+        util._run_finalizers()
+
         with self._lock:
             if self._fd is not None:
                 # resource tracker was launched before, is it still running?
diff --git a/Misc/NEWS.d/next/Library/2023-09-20-18-28-12.gh-issue-109593.VVWJDC.rst b/Misc/NEWS.d/next/Library/2023-09-20-18-28-12.gh-issue-109593.VVWJDC.rst
new file mode 100644
index 000000000000000..d60640cd2aab863
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2023-09-20-18-28-12.gh-issue-109593.VVWJDC.rst
@@ -0,0 +1,3 @@
+:mod:`multiprocessing`: Reduce the risk of reentrant calls to
+``ResourceTracker.ensure_running()`` by running explicitly all finalizers
+before acquiring the ``ResourceTracker`` lock. Patch by Victor Stinner.