Assertion failed: Python/qsbr.c in _Py_qsbr_poll

[colesbury]

Crash report

Seen in https://github.com/python/cpython/actions/runs/15239974615/job/42858835898

0:07:45 load avg: 8.75 [57/60/1] test_free_threading worker non-zero exit code (Exit code -6 (SIGABRT)) -- running (2): test_socket (1 min 55 sec), test_threading (37.6 sec)
python: Python/qsbr.c:164: _Bool _Py_qsbr_poll(struct _qsbr_thread_state *, uint64_t): Assertion `((_PyThreadStateImpl *)_PyThreadState_GET())->qsbr == qsbr' failed.
Fatal Python error: Aborted

<Cannot show all threads while the GIL is disabled>
Stack (most recent call first):
  File "/home/runner/work/cpython/cpython/Lib/test/test_free_threading/test_dict.py", line 185 in writer_func
  File "/home/runner/work/cpython/cpython/Lib/threading.py", line 1016 in run
  File "/home/runner/work/cpython/cpython/Lib/threading.py", line 1074 in _bootstrap_inner
  File "/home/runner/work/cpython/cpython/Lib/threading.py", line 1036 in _bootstrap

Current thread's C stack trace (most recent call first):
python: Python/qsbr.c:164: _Bool _Py_qsbr_poll(struct _qsbr_thread_state *, uint64_t): Assertion `((_PyThreadStateImpl *)_PyThreadState_GET())->qsbr == qsbr' failed.

cpython/Lib/test/test_free_threading/test_dict.py

Line 185 in a32ea45

f.__dict__ = d

cpython/Python/qsbr.c

Lines 160 to 164 in a32ea45

	bool
	_Py_qsbr_poll(struct _qsbr_thread_state *qsbr, uint64_t goal)
	{
	assert(_Py_atomic_load_int_relaxed(&_PyThreadState_GET()->state) == _Py_THREAD_ATTACHED);
	assert(((_PyThreadStateImpl *)_PyThreadState_GET())->qsbr == qsbr);

Linked PRs

• gh-134679: Fix assertion failure in QSBR #134811
• [3.14] gh-134679: Fix assertion failure in QSBR (gh-134811) #134814

[colesbury]

This is basically the same issue as #130519, but with tstate->qsbr instead of the work queue.