ch6 - Chapter 6 Deadlock Concurrency: Deadlock 1...

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Concurrency: Deadlock 1 ©Magee/Kramer 2 nd Edition Chapter 6 Deadlock
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Concurrency: Deadlock 2 ©Magee/Kramer 2 nd Edition Deadlock Concepts : system deadlock : no further progress Models : deadlock - no eligible actions Practice : blocked threads Aim : deadlock avoidance - to design systems where deadlock cannot occur.
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Concurrency: Deadlock 3 ©Magee/Kramer 2 nd Edition Deadlock: four necessary and sufficient conditions Serially reusable resources: the processes involved share resources which they use under mutual exclusion. Incremental acquisition: processes hold on to resources already allocated to them while waiting to acquire additional resources. No pre-emption: once acquired by a process, resources cannot be pre-empted (forcibly withdrawn) but are only released voluntarily. Wait-for cycle: a circular chain (or cycle) of processes exists such that each process holds a resource which its successor in the cycle is waiting to acquire.
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Concurrency: Deadlock 4 ©Magee/Kramer 2 nd Edition Wait-for cycle A B C D E Has A awaits B Has B awaits C Has C awaits D Has D awaits E Has E awaits A
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Concurrency: Deadlock 5 ©Magee/Kramer 2 nd Edition 6.1 Deadlock analysis - primitive processes deadlocked state is one with no outgoing transitions in FSP: STOP process MOVE = (north->(south->MOVE|north-> STOP )). Trace to DEADLOCK: north north animation to produce a trace. analysis using LTSA : (shortest trace to STOP ) MOVE north north south 0 1 2
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Concurrency: Deadlock 6 ©Magee/Kramer 2 nd Edition deadlock analysis - parallel composition in systems, deadlock may arise from the parallel composition of interacting processes. RESOURCE = (get->put->RESOURCE). P = ( printer.get -> scanner.get ->copy ->printer.put->scanner.put ->P). Q = (
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ch6 - Chapter 6 Deadlock Concurrency: Deadlock 1...

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