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+<TITLE>Priority Inversion Protocol</TITLE>
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+<H2>Proving the Priority Inheritance Protocol Correct</H2>
+
+By Xingyuan Zhang, Christian Urban and Chunhan Wu
+<p>
+In real-time systems with threads, resource locking and
+priority scheduling, one faces the problem of Priority
+Inversion. This problem can make the behaviour of threads
+unpredictable and the resulting bugs can be hard to find. The
+Priority Inheritance Protocol is one solution implemented in many
+systems for solving this problem, but the correctness of this solution
+has never been formally verified in a theorem prover. As already
+pointed out in the literature, the original informal investigation of
+the Property Inheritance Protocol presents a correctness "proof" for
+an incorrect algorithm. In this paper we fix the problem of
+this proof by making all notions precise and implementing a variant of
+a solution proposed earlier. Our formalisation in Isabelle/HOL
+uncovers facts not mentioned in the literature, but also shows how to
+efficiently implement this protocol. Earlier correct implementations
+were criticised as too inefficient. Our formalisation is based on
+Paulson's inductive approach to verifying protocols.
+<BR><BR>
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