threading.py 文件源码

def _after_fork():
    # This function is called by Python/ceval.c:PyEval_ReInitThreads which
    # is called from PyOS_AfterFork.  Here we cleanup threading module state
    # that should not exist after a fork.

    # Reset _active_limbo_lock, in case we forked while the lock was held
    # by another (non-forked) thread.  http://bugs.python.org/issue874900
    global _active_limbo_lock
    _active_limbo_lock = _allocate_lock()

    # fork() only copied the current thread; clear references to others.
    new_active = {}
    current = current_thread()
    with _active_limbo_lock:
        for thread in _active.itervalues():
            if thread is current:
                # There is only one active thread. We reset the ident to
                # its new value since it can have changed.
                ident = _get_ident()
                thread._Thread__ident = ident
                # Any condition variables hanging off of the active thread may
                # be in an invalid state, so we reinitialize them.
                if hasattr(thread, '_reset_internal_locks'):
                    thread._reset_internal_locks()
                new_active[ident] = thread
            else:
                # All the others are already stopped.
                # We don't call _Thread__stop() because it tries to acquire
                # thread._Thread__block which could also have been held while
                # we forked.
                thread._Thread__stopped = True

        _limbo.clear()
        _active.clear()
        _active.update(new_active)
        assert len(_active) == 1


# Self-test code