GeezerVison

$ ./python bug.py 
python: Python/pystate.c:2904: _PyThreadState_CheckConsistency: Assertion `!_PyMem_IsPtrFreed(tstate->interp)' failed.
Abandon (core dumped)

$ gdb -args ./python bug.py 
(gdb) run
Starting program: /home/vstinner/python/main/python bug.py
[New Thread 0x7fffea2ff6c0 (LWP 1148671)]
[New Thread 0x7fffe9afe6c0 (LWP 1148672)]
python: Python/pystate.c:2904: _PyThreadState_CheckConsistency: Assertion `!_PyMem_IsPtrFreed(tstate->interp)' failed.

Thread 3 "python" received signal SIGABRT, Aborted.
[Switching to Thread 0x7fffe9afe6c0 (LWP 1148672)]
0x00007ffff7d7a844 in __pthread_kill_implementation () from /lib64/libc.so.6

(gdb) where
#0  0x00007ffff7d7a844 in __pthread_kill_implementation () from /lib64/libc.so.6
#1  0x00007ffff7d29abe in raise () from /lib64/libc.so.6
#2  0x00007ffff7d1287f in abort () from /lib64/libc.so.6
#3  0x00007ffff7d1279b in __assert_fail_base.cold () from /lib64/libc.so.6
#4  0x00007ffff7d22147 in __assert_fail () from /lib64/libc.so.6
#5  0x00000000006e204a in _PyThreadState_CheckConsistency (tstate=0x7fffe4000e50) at Python/pystate.c:2904
#6  0x000000000078f006 in thread_run (boot_raw=0x7fffea4be1b0) at ./Modules/_threadmodule.c:1081
#7  0x00000000006ff043 in pythread_wrapper (arg=0xb86580) at Python/thread_pthread.h:233
#8  0x00007ffff7d78907 in start_thread () from /lib64/libc.so.6
#9  0x00007ffff7dfe870 in clone3 () from /lib64/libc.so.6

diff --git a/Modules/_threadmodule.c b/Modules/_threadmodule.c
index 49f34fcb9f..f5fc209e88 100644
--- a/Modules/_threadmodule.c
+++ b/Modules/_threadmodule.c
@@ -1158,11 +1161,13 @@ thread_PyThread_start_new_thread(PyObject *self, PyObject *fargs)
                         "thread is not supported for isolated subinterpreters");
         return NULL;
     }
+#if 0
     if (interp->finalizing) {
         PyErr_SetString(PyExc_RuntimeError,
                         "can't create new thread at interpreter shutdown");
         return NULL;
     }
+#endif

     struct bootstate *boot = PyMem_NEW(struct bootstate, 1);
     if (boot == NULL) {

import atexit
import threading

def t0():
    pass

def t1():
    threading.Thread(target=t0).start()

def f():
    threading.Thread(target=t1).start()

atexit.register(f)
exit()

Assertion failed: tstate_is_alive(tstate) && !tstate->_status.bound, file D:\\a\\cpython\\cpython\\Python\\pystate.c, line 245

static void
bind_tstate(PyThreadState *tstate)
{
    assert(tstate != NULL);
    assert(tstate_is_alive(tstate) && !tstate->_status.bound); /// <=== HERE, line 245
    assert(!tstate->_status.unbound);  // just in case
    assert(!tstate->_status.bound_gilstate);
    assert(tstate != gilstate_tss_get(tstate->interp->runtime));
    assert(!tstate->_status.active);
    assert(tstate->thread_id == 0);
    assert(tstate->native_thread_id == 0);

Assertion failed: !_PyMem_IsPtrFreed(tstate->interp), file C:\victor\python\main\Python\pystate.c, line 2911
Fatal Python error: Aborted

Thread 0x00000ef0 (most recent call first):
  <no Python frame>