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25 <H2>Proving the Priority Inheritance Protocol Correct</H2> |
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26 |
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27 By Xingyuan Zhang, Christian Urban and Chunhan Wu |
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28 <p> |
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29 In real-time systems with threads, resource locking and |
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30 priority scheduling, one faces the problem of Priority |
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31 Inversion. This problem can make the behaviour of threads |
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32 unpredictable and the resulting bugs can be hard to find. The |
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33 Priority Inheritance Protocol is one solution implemented in many |
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34 systems for solving this problem, but the correctness of this solution |
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35 has never been formally verified in a theorem prover. As already |
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36 pointed out in the literature, the original informal investigation of |
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37 the Property Inheritance Protocol presents a correctness "proof" for |
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38 an incorrect algorithm. In this paper we fix the problem of |
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39 this proof by making all notions precise and implementing a variant of |
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40 a solution proposed earlier. Our formalisation in Isabelle/HOL |
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41 uncovers facts not mentioned in the literature, but also shows how to |
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42 efficiently implement this protocol. Earlier correct implementations |
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43 were criticised as too inefficient. Our formalisation is based on |
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44 Paulson's inductive approach to verifying protocols. |
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