\documentclass[runningheads]{llncs}\usepackage{isabelle}\usepackage{isabellesym}\usepackage{amsmath}\usepackage{amssymb}\usepackage{mathpartir}\usepackage{tikz}\usepackage{pgf}%\usetikzlibrary{arrows,automata,decorations,fit,calc}%\usetikzlibrary{shapes,shapes.arrows,snakes,positioning}%\usepgflibrary{shapes.misc} % LATEX and plain TEX and pure pgf%\usetikzlibrary{matrix}\usepackage{pdfsetup}\usepackage{ot1patch}\usepackage{times}%%\usepackage{proof}%%\usepackage{mathabx}\usepackage{stmaryrd}\usepackage{url}\usepackage{color}\titlerunning{Proving the Priority Inheritance Protocol Correct}\urlstyle{rm}\isabellestyle{it}\renewcommand{\isastyleminor}{\it}%\renewcommand{\isastyle}{\normalsize\it}%\def\dn{\,\stackrel{\mbox{\scriptsize def}}{=}\,}\renewcommand{\isasymequiv}{$\dn$}\renewcommand{\isasymemptyset}{$\varnothing$}\renewcommand{\isacharunderscore}{\mbox{$\_\!\_$}}\renewcommand{\isasymiota}{}\newcommand{\numbered}[1]{\refstepcounter{equation}{\rm(\arabic{equation})}\label{#1}}\definecolor{mygrey}{rgb}{.80,.80,.80}\begin{document}\title{Priority Inheritance Protocol Proved Correct}\author{Xingyuan Zhang\inst{1} \and Christian Urban\inst{2} \and Chunhan Wu\inst{1}}\institute{PLA University of Science and Technology, China \and King's College London, United Kingdom}\maketitle\begin{abstract}In real-time systems with threads, resource locking and priority sched\-uling, one faces the problem of PriorityInversion. This problem can make the behaviour of threadsunpredictable and the resulting bugs can be hard to find. ThePriority Inheritance Protocol is one solution implemented in manysystems for solving this problem, but the correctness of this solutionhas never been formally verified in a theorem prover. As alreadypointed out in the literature, the original informal investigation ofthe Property Inheritance Protocol presents a correctness ``proof'' foran \emph{incorrect} algorithm. In this paper we fix the problem ofthis proof by making all notions precise and implementing a variant ofa solution proposed earlier. Our formalisation in Isabelle/HOLuncovers facts not mentioned in the literature, but also shows how toefficiently implement this protocol. Earlier correct implementationswere criticised as too inefficient. Our formalisation is based onPaulson's inductive approach to verifying protocols.\medskip{\bf Keywords:} Priority Inheritance Protocol, formal correctness proof, real-time systems, Isabelle/HOL\end{abstract}\input{session}%\bibliographystyle{plain}%\bibliography{root}\end{document}%%% Local Variables:%%% mode: latex%%% TeX-master: t%%% End: