[3.11] gh-108987: Fix _thread.start_new_thread() race condition (#109135)

[vstinner]

Fix _thread.start_new_thread() race condition. If a thread is created during Python finalization, the newly spawned thread now exits immediately instead of trying to access freed memory and lead to a crash.

thread_run() calls PyEval_AcquireThread() which checks if the thread must exit. The problem was that tstate was dereferenced earlier in _PyThreadState_Bind() which leads to a crash most of the time.

Move _PyThreadState_CheckConsistency() from thread_run() to _PyThreadState_Bind().

(cherry picked from commit 517cd82)

• Issue: test_threading fails and crashes when rerun #108987

[vstinner]

I tested manually this fix, it works as I expected.

I used this test: #109135 (comment)

Without this change: CRASH!

(...)
-- sleep 100 ms before PyEval_AcquireThread() --
-- sleep 100 ms before PyEval_AcquireThread() --
-- sleep 100 ms before PyEval_AcquireThread() --
-- sleep 100 ms before PyEval_AcquireThread() --
-- sleep 100 ms before PyEval_AcquireThread() --
-- sleep 100 ms before PyEval_AcquireThread() --
-- sleep 100 ms before PyEval_AcquireThread() --
exit
-- sleep 1 sec after free_interpreter() --
python: Python/pystate.c:2259: _PyThreadState_CheckConsistency: Assertion `!_PyMem_IsPtrFreed(tstate->interp)' failed.
python: Python/pystate.c:2259: _PyThreadState_CheckConsistency: Assertion `!_PyMem_IsPtrFreed(tstate->interp)' failed.
python: Python/pystate.c:2259: _PyThreadState_CheckConsistency: Assertion `!_PyMem_IsPtrFreed(tstate->interp)' failed.
python: Python/pystate.c:2259: _PyThreadState_CheckConsistency: Assertion `!_PyMem_IsPtrFreed(tstate->interp)' failed.
Abandon (core dumped)

With this change: not crash.

$ ./python bug.py; echo "exitcode=$?"
(...)
-- sleep 100 ms before PyEval_AcquireThread() --
-- sleep 100 ms before PyEval_AcquireThread() --
-- sleep 100 ms before PyEval_AcquireThread() --
-- sleep 100 ms before PyEval_AcquireThread() --
-- sleep 100 ms before PyEval_AcquireThread() --
-- sleep 100 ms before PyEval_AcquireThread() --
-- sleep 100 ms before PyEval_AcquireThread() --
-- sleep 100 ms before PyEval_AcquireThread() --
exit
-- sleep 1 sec after free_interpreter() --
exitcode=0