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  No pre-emption:  once acquired by a process, resources cannot  be pre-empted (forcibly withdrawn) but are only  released voluntarily.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 = (
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This note was uploaded on 02/08/2012 for the course CSCI 6232 taught by Professor Rotenstreich during the Spring '11 term at GWU.

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

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