gh-109746: Make _thread.start_new_thread delete state of new thread on its startup failure

Lib/test/test_threading.py

@@ -1171,6 +1171,40 @@ def __del__(self):
  self.assertEqual(out.strip(), b"OK")
  self.assertIn(b"can't create new thread at interpreter shutdown", err)
 
+ def test_start_new_thread_failed(self):
+ # gh-109746: if Python fails to start newly created thread
+ # due to failure of underlying PyThread_start_new_thread() call,
+ # its state should be removed from interpreter' thread states list
+ # to avoid its double cleanup
+ try:
+ from resource import setrlimit, RLIMIT_NPROC
+ except ImportError as err:
+ self.skipTest(err) # RLIMIT_NPROC is specific to Linux and BSD
+ code = """if 1:
+ import resource
+ import _thread
+
+ def f():
+ print("shouldn't be printed")
+
+ limits = resource.getrlimit(resource.RLIMIT_NPROC)
+ [_, hard] = limits
+ resource.setrlimit(resource.RLIMIT_NPROC, (0, hard))
+
+ try:
+ _thread.start_new_thread(f, ())
+ except RuntimeError:
+ print('ok')
+ else:
+ print('skip')
+ """
+ _, out, err = assert_python_ok("-u", "-c", code)
+ out = out.strip()
+ if out == b'skip':
+ self.skipTest('RLIMIT_NPROC had no effect; probably superuser')
+ self.assertEqual(out, b'ok')
+ self.assertEqual(err, b'')
+
  @cpython_only
  def test_finalize_daemon_thread_hang(self):
  if support.check_sanitizer(thread=True, memory=True):

Misc/NEWS.d/next/Core_and_Builtins/2023-09-22-21-01-56.gh-issue-109746.32MHt9.rst

@@ -0,0 +1 @@
+If :func:`!_thread.start_new_thread` fails to start a new thread, it deletes its state from interpreter and thus avoids its repeated cleanup on finalization.

Modules/_threadmodule.c

@@ -421,6 +421,7 @@ ThreadHandle_start(ThreadHandle *self, PyObject *func, PyObject *args,
  PyThread_handle_t os_handle;
  if (PyThread_start_joinable_thread(thread_run, boot, &ident, &os_handle)){
  PyThreadState_Clear(boot->tstate);
+ PyThreadState_Delete(boot->tstate);
  thread_bootstate_free(boot, 1);
  PyErr_SetString(ThreadError, "can't start new thread");
  goto start_failed;

Python/pystate.c

@@ -1779,7 +1779,9 @@ tstate_delete_common(PyThreadState *tstate, int release_gil)
  if (tstate->_status.bound_gilstate){
  unbind_gilstate_tstate(tstate);
  }
- unbind_tstate(tstate);
+ if (tstate->_status.bound){
+ unbind_tstate(tstate);
+ }
 
  // XXX Move to PyThreadState_Clear()?
  clear_datastack(tstate);