On Cyclic Process Dependencies and the Veriication of Absence of Deadlocks in Reactive Systems
نویسندگان
چکیده
We introduce the class of weak process dependency relations, and give deenitions of starvation and deadlock cycles in terms of these. We show the usefulness of our deenitions in reasoning about deadlocks, in the general sense of all forms of innnite process suspension, including the local form also known as livelock. In particular, we make a formal distinction between three complementary cases of deadlock: starvation, deadlock cycles, and a form we call non-closing deadlocks. Furthermore, we state assumptions under which absence of deadlocks may be veriied for a program by verifying absence of deadlock cycles, and discuss when dependencies between deadlocked processes can safely be excluded. We give a generalised framework for verifying absence of deadlock cycles, in terms of our deenitions, extending the method developed by Stephen P. Masticola to local deadlocks. Lastly, we demonstrate how Masticola's method can be mapped onto our framework, and brieey discuss the relation between resource allocation dependencies and weak process dependency relations.
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