Issue #18808: Thread.join() now waits for the underlying thread state to be destroyed before returning.
This prevents unpredictable aborts in Py_EndInterpreter() when some non-daemon threads are still running.
diff --git a/Modules/_threadmodule.c b/Modules/_threadmodule.c
index cbb2901..d83d117 100644
--- a/Modules/_threadmodule.c
+++ b/Modules/_threadmodule.c
@@ -1172,6 +1172,66 @@
This function is meant for internal and specialized purposes only.\n\
In most applications `threading.enumerate()` should be used instead.");
+static void
+release_sentinel(void *wr)
+{
+ /* Tricky: this function is called when the current thread state
+ is being deleted. Therefore, only simple C code can safely
+ execute here. */
+ PyObject *obj = PyWeakref_GET_OBJECT(wr);
+ lockobject *lock;
+ if (obj != Py_None) {
+ assert(Py_TYPE(obj) == &Locktype);
+ lock = (lockobject *) obj;
+ if (lock->locked) {
+ PyThread_release_lock(lock->lock_lock);
+ lock->locked = 0;
+ }
+ }
+ /* Deallocating a weakref with a NULL callback only calls
+ PyObject_GC_Del(), which can't call any Python code. */
+ Py_DECREF(wr);
+}
+
+static PyObject *
+thread__set_sentinel(PyObject *self)
+{
+ PyObject *wr;
+ PyThreadState *tstate = PyThreadState_Get();
+ lockobject *lock;
+
+ if (tstate->on_delete_data != NULL) {
+ /* We must support the re-creation of the lock from a
+ fork()ed child. */
+ assert(tstate->on_delete == &release_sentinel);
+ wr = (PyObject *) tstate->on_delete_data;
+ tstate->on_delete = NULL;
+ tstate->on_delete_data = NULL;
+ Py_DECREF(wr);
+ }
+ lock = newlockobject();
+ if (lock == NULL)
+ return NULL;
+ /* The lock is owned by whoever called _set_sentinel(), but the weakref
+ hangs to the thread state. */
+ wr = PyWeakref_NewRef((PyObject *) lock, NULL);
+ if (wr == NULL) {
+ Py_DECREF(lock);
+ return NULL;
+ }
+ tstate->on_delete_data = (void *) wr;
+ tstate->on_delete = &release_sentinel;
+ return (PyObject *) lock;
+}
+
+PyDoc_STRVAR(_set_sentinel_doc,
+"_set_sentinel() -> lock\n\
+\n\
+Set a sentinel lock that will be released when the current thread\n\
+state is finalized (after it is untied from the interpreter).\n\
+\n\
+This is a private API for the threading module.");
+
static PyObject *
thread_stack_size(PyObject *self, PyObject *args)
{
@@ -1247,6 +1307,8 @@
METH_NOARGS, _count_doc},
{"stack_size", (PyCFunction)thread_stack_size,
METH_VARARGS, stack_size_doc},
+ {"_set_sentinel", (PyCFunction)thread__set_sentinel,
+ METH_NOARGS, _set_sentinel_doc},
{NULL, NULL} /* sentinel */
};