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https://github.com/python/cpython/commit/7cb3a4474731f52c74b19dd3c99ca06e227dae3b
commit: 7cb3a4474731f52c74b19dd3c99ca06e227dae3b
branch: 3.9
author: Kumar Aditya <59607654+kumaraditya303@users.noreply.github.com>
committer: ambv <lukasz@langa.pl>
date: 2023-03-28T10:55:36+02:00
summary:

[3.9] GH-102126: fix deadlock at shutdown when clearing thread states (GH-102222) (#102236)

(cherry picked from commit 5f11478ce7fda826d399530af4c5ca96c592f144)

files:
A Misc/NEWS.d/next/Core and Builtins/2023-02-24-17-59-39.gh-issue-102126.HTT8Vc.rst
M Python/pystate.c

diff --git a/Misc/NEWS.d/next/Core and Builtins/2023-02-24-17-59-39.gh-issue-102126.HTT8Vc.rst b/Misc/NEWS.d/next/Core and Builtins/2023-02-24-17-59-39.gh-issue-102126.HTT8Vc.rst
new file mode 100644
index 000000000000..68c43688c3df
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2023-02-24-17-59-39.gh-issue-102126.HTT8Vc.rst
@@ -0,0 +1 @@
+Fix deadlock at shutdown when clearing thread states if any finalizer tries to acquire the runtime head lock. Patch by Kumar Aditya.
diff --git a/Python/pystate.c b/Python/pystate.c
index c3520c336a79..1cf9be1eabb7 100644
--- a/Python/pystate.c
+++ b/Python/pystate.c
@@ -288,11 +288,19 @@ PyInterpreterState_Clear(PyInterpreterState *interp)
_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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