pythongh-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.
vstinner · Sep 20, 2023 · 339467e · 339467e
1 parent ced6924
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diff --git 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
@@ -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.