We study the safety verification problem for parameterized systems under the release-acquire (RA) semantics. It has been shown that the problem is intractable for systems with unlimited access to atomic compare-and-swap (CAS) instructions. We show that, from a verification perspective where approximate results help, this is overly pessimistic. We study parameterized systems consisting of an unbounded number of environment threads executing identical but CAS-free programs and a fixed number of distinguished threads that are unrestricted. Our first contribution is a new semantics that considerably simplifies RA but is still equivalent for the above systems as far as safety verification is concerned. We apply this (general) result to two subclasses of our model. We show that safety verification is only \pspace-complete for the bounded model checking problem where the distinguished threads are loop-free. Interestingly, we can still afford the unbounded environment. We show that the complexity jumps to \nexp-complete for thread-modular verification where an unrestricted distinguished `ego' thread interacts with an environment of CAS-free threads plus loop-free distinguished threads (as in the earlier setting). Besides the usefulness for verification, the results are strong in that they delineate the tractability border for an established semantics.

中文翻译：

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发布-获取下参数化系统的安全验证

我们研究了基于发布获取（RA）语义的参数化系统的安全验证问题。已经表明，对于无限制访问原子比较和交换（CAS）指令的系统，该问题是棘手的。我们证明，从验证结果有帮助的角度来看，这过于悲观。我们研究了参数化系统，该系统由无数个环境线程组成，这些线程执行相同但无CAS的程序，并有固定数量的不受限制的专有线程。我们的第一个贡献是一种新的语义，它大大简化了RA，但就安全性验证而言，对于上述系统仍然是等效的。我们将此（一般）结果应用于模型的两个子类。我们显示出安全验证仅对有界线模型无循环的有界模型检查问题具有\ pspace-complete。有趣的是，我们仍然可以负担得起无限制的环境。我们显示，对于线程模块化验证，复杂性跃升为\ nexp-complete，其中无限制的专有“ ego”线程与无CAS线程加无循环专有线程的环境进行交互（如先前的设置）。除了对验证有用之外，结果还很强大，因为它们描绘了既定语义的易处理性边界。线程与无CAS线程以及无循环的专有线程（如先前设置）的环境进行交互。除了对验证有用之外，结果还很强大，因为它们描绘了既定语义的易处理性边界。线程与无CAS线程以及无循环的专有线程（如先前设置）的环境进行交互。除了对验证有用之外，结果还很强大，因为它们描绘了既定语义的易处理性边界。