From: Miss Islington (bot) <31488909+miss-islington@users.noreply.github.com>
Date: Sat, 18 Oct 2025 11:28:53 +0000 (+0200)
Subject: [3.14] gh-140257: fix data race on eval_breaker during finalization (GH-140265) ... 
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=3ca7ea1f8fd593296106346b4dea06f126638aba;p=thirdparty%2FPython%2Fcpython.git

[3.14] gh-140257: fix data race on eval_breaker during finalization (GH-140265) (#140294)

gh-140257: fix data race on eval_breaker during finalization (GH-140265)
(cherry picked from commit c8729c9909e150989050ce2a435d018955bea41d)

Co-authored-by: Shamil <ashm.tech@proton.me>
---

diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2025-10-17-20-23-19.gh-issue-140257.8Txmem.rst b/Misc/NEWS.d/next/Core_and_Builtins/2025-10-17-20-23-19.gh-issue-140257.8Txmem.rst
new file mode 100644
index 000000000000..50f7e0e48ae3
--- /dev/null
+++ b/Misc/NEWS.d/next/Core_and_Builtins/2025-10-17-20-23-19.gh-issue-140257.8Txmem.rst
@@ -0,0 +1,2 @@
+Fix data race between interpreter_clear() and take_gil() on eval_breaker
+during finalization with daemon threads.
diff --git a/Python/pystate.c b/Python/pystate.c
index 6859dbc9a7f4..9f6e961e71ae 100644
--- a/Python/pystate.c
+++ b/Python/pystate.c
@@ -860,10 +860,11 @@ interpreter_clear(PyInterpreterState *interp, PyThreadState *tstate)
 
     Py_CLEAR(interp->audit_hooks);
 
-    // At this time, all the threads should be cleared so we don't need atomic
-    // operations for instrumentation_version or eval_breaker.
+    // gh-140257: Threads have already been cleared, but daemon threads may
+    // still access eval_breaker atomically via take_gil() right before they
+    // hang. Use an atomic store to prevent data races during finalization.
     interp->ceval.instrumentation_version = 0;
-    tstate->eval_breaker = 0;
+    _Py_atomic_store_uintptr(&tstate->eval_breaker, 0);
 
     for (int i = 0; i < _PY_MONITORING_UNGROUPED_EVENTS; i++) {
         interp->monitors.tools[i] = 0;