bpo-40089: Add _at_fork_reinit() method to locks (GH-19195)
Add a private _at_fork_reinit() method to _thread.Lock,
_thread.RLock, threading.RLock and threading.Condition classes:
reinitialize the lock after fork in the child process; reset the lock
to the unlocked state.
Rename also the private _reset_internal_locks() method of
threading.Event to _at_fork_reinit().
* Add _PyThread_at_fork_reinit() private function. It is excluded
from the limited C API.
* threading.Thread._reset_internal_locks() now calls
_at_fork_reinit() on self._tstate_lock rather than creating a new
Python lock object.
diff --git a/Include/pythread.h b/Include/pythread.h
index 1cf83b7..bb9d864 100644
--- a/Include/pythread.h
+++ b/Include/pythread.h
@@ -36,6 +36,15 @@
#define WAIT_LOCK 1
#define NOWAIT_LOCK 0
+#ifndef Py_LIMITED_API
+#ifdef HAVE_FORK
+/* Private function to reinitialize a lock at fork in the child process.
+ Reset the lock to the unlocked state.
+ Return 0 on success, return -1 on error. */
+PyAPI_FUNC(int) _PyThread_at_fork_reinit(PyThread_type_lock *lock);
+#endif /* HAVE_FORK */
+#endif /* !Py_LIMITED_API */
+
/* PY_TIMEOUT_T is the integral type used to specify timeouts when waiting
on a lock (see PyThread_acquire_lock_timed() below).
PY_TIMEOUT_MAX is the highest usable value (in microseconds) of that