[Python-checkins] GH-102126: fix deadlock at shutdown when clearing thread states (#102222)
kumaraditya303
webhook-mailer at python.org
Sat Feb 25 01:52:13 EST 2023
https://github.com/python/cpython/commit/5f11478ce7fda826d399530af4c5ca96c592f144
commit: 5f11478ce7fda826d399530af4c5ca96c592f144
branch: main
author: Kumar Aditya <59607654+kumaraditya303 at users.noreply.github.com>
committer: kumaraditya303 <59607654+kumaraditya303 at users.noreply.github.com>
date: 2023-02-25T12:21:36+05:30
summary:
GH-102126: fix deadlock at shutdown when clearing thread states (#102222)
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 32b17fd19e34..3c655bf38958 100644
--- a/Python/pystate.c
+++ b/Python/pystate.c
@@ -754,12 +754,19 @@ interpreter_clear(PyInterpreterState *interp, PyThreadState *tstate)
_PyErr_Clear(tstate);
}
+ // Clear the current/main thread state last.
HEAD_LOCK(runtime);
- // XXX Clear the current/main thread state last.
- for (PyThreadState *p = interp->threads.head; p != NULL; p = p->next) {
+ PyThreadState *p = interp->threads.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);
/* It is possible that any of the objects below have a finalizer
that runs Python code or otherwise relies on a thread state
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