Locking protocol is a crucial component in scheduling of real-time systems. The digraph real-time task model (DRT) is the state-of-the-art graph-based task model, which is a generalization of most previous real-time task models. To our best knowledge, the only work addressing resource sharing problem in DRT task model proposes a resource sharing protocol, called ACP, as well as a scheduling strategy EDF+ACP. Although EDF+ACP is optimal for scheduling DRT tasks with non-nested resource access, it can not handle the situation of nested resource accesses. In this paper, we propose a new protocol, called N-ACP, by modifying ACP to manage nested resource accesses in task graph models. We apply N-ACP to EDF scheduling to obtain a new scheduling strategy EDF+N-ACP. We develop schedulability analysis techniques for EDF+N-ACP and evaluate its performance by a widely-used quantitative metrics speedup factor. We derive its speedup factor as a function of the maximal nesting level of resource accesses in the system.

锁定协议是实时系统调度中的关键组成部分。有向图实时任务模型（DRT）是基于图形的最新任务模型，是对大多数以前的实时任务模型的概括。据我们所知，解决DRT任务模型中资源共享问题的唯一工作是提出一种称为ACP的资源共享协议以及一种调度策略EDF + ACP。尽管EDF + ACP最适合用于调度具有非嵌套资源访问的DRT任务，但它不能处理嵌套资源访问的情况。在本文中，我们通过修改ACP来管理任务图模型中的嵌套资源访问，提出了一种称为N-ACP的新协议。我们将N-ACP应用于EDF调度，以获得新的调度策略EDF + N-ACP。我们为EDF + N-ACP开发了可调度性分析技术，并通过广泛使用的量化指标加速因子来评估其性能。我们得出其加速因子是系统中资源访问的最大嵌套级别的函数。