lect-07 - Computer Science 425 Distributed Systems Lecture...

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Lecture 7-1 2006, 2007, M. T. Harandi Computer Science 425 Distributed Systems Lecture 7 Global States
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Lecture 7-2 2006, 2007, M. T. Harandi Detecting Global Properties p 2 p 1 message garbage object object reference a. Garbage collection p 2 p 1 wait-for wait-for b. Deadlock p 2 p 1 activate passive passive c. Termination
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Lecture 7-3 2006, 2007, M. T. Harandi Process Histories and States For a process P i , history(P i ) = h i = <e i 0 , e i 1 , … > prefix history(P i k ) = h i k = <e i 0 , e i 1 , …,e i k > S i k : P i ‘s state immediately before k th event For a set of processes, global history: H = i (h i ) global state: S = i (S i k i ) a cut C H = h 1 c1 h 2 c2 h n cn the frontier of C = {e i ci , i = 1,2, … n}
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Lecture 7-4 2006, 2007, M. T. Harandi Consistent States A cut C is consistent if 2200 e C (if f e then f C) A global state S is consistent if it corresponds to a consistent cut P1 P2 P3 e 1 0 e 1 1 e 1 2 e 1 3 e 2 0 e 2 1 e 2 2 e 3 0 e 3 1 e 3 2 Inconsistent cut Consistent cut
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Lecture 7-5 2006, 2007, M. T. Harandi Global States A Run is a total ordering of events in H that is consistent with each h i ’s ordering A Linearization is a run consistent with happens- before ( ) relation in H.
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