From 5f11478ce7fda826d399530af4c5ca96c592f144 Mon Sep 17 00:00:00 2001 From: Kumar Aditya <59607654+kumaraditya303@users.noreply.github.com> Date: Sat, 25 Feb 2023 12:21:36 +0530 Subject: [PATCH] GH-102126: fix deadlock at shutdown when clearing thread states (#102222) --- ...2023-02-24-17-59-39.gh-issue-102126.HTT8Vc.rst | 1 + Python/pystate.c | 15 +++++++++++---- 2 files changed, 12 insertions(+), 4 deletions(-) create mode 100644 Misc/NEWS.d/next/Core and Builtins/2023-02-24-17-59-39.gh-issue-102126.HTT8Vc.rst 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 00000000000..68c43688c3d --- /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 32b17fd19e3..3c655bf3895 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_Clear(p); - } + 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); + } /* It is possible that any of the objects below have a finalizer that runs Python code or otherwise relies on a thread state