From 6c2e052ee07f10a6336bb4de1cef71dbe7d30ee6 Mon Sep 17 00:00:00 2001
From: Kumar Aditya <59607654+kumaraditya303@users.noreply.github.com>
Date: Fri, 3 Mar 2023 18:44:30 +0530
Subject: =?UTF-8?q?[3.10]=20GH-102126:=20fix=20deadlock=20at=20shutdown=20?=
 =?UTF-8?q?when=20clearing=20thread=20state=E2=80=A6=20(#102235)?=
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[3.10] GH-102126: fix deadlock at shutdown when clearing thread states (GH-102222).
(cherry picked from commit 5f11478ce7fda826d399530af4c5ca96c592f144)
---
 Python/pystate.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

(limited to 'Python/pystate.c')

diff --git a/Python/pystate.c b/Python/pystate.c
index df98eb11bb..c7a6af5da8 100644
--- a/Python/pystate.c
+++ b/Python/pystate.c
@@ -293,11 +293,19 @@ interpreter_clear(PyInterpreterState *interp, PyThreadState *tstate)
         _PyErr_Clear(tstate);
     }
 
+    // Clear the current/main thread state last.
     HEAD_LOCK(runtime);
-    for (PyThreadState *p = interp->tstate_head; p != NULL; p = p->next) {
+    PyThreadState *p = interp->tstate_head;
+    HEAD_UNLOCK(runtime);
+    while (p != NULL) {
+        // See https://github.com/python/cpython/issues/102126
+        // Must be called without HEAD_LOCK held as it can deadlock
+        // if any finalizer tries to acquire that lock.
         PyThreadState_Clear(p);
+        HEAD_LOCK(runtime);
+        p = p->next;
+        HEAD_UNLOCK(runtime);
     }
-    HEAD_UNLOCK(runtime);
 
     Py_CLEAR(interp->audit_hooks);
 
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