2015Q2
1.(30P) What are advantages and disadvantages of Mutual Exclusion by Message Passing? 
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It supports resource sharing in distributed system, but when we use it on the same computer, it is very slower than other concurrency primitives.
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2.(40P) What properties must be in scheduling algorithms? 
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Fairness - giving each process a fair share of the CPU
Policy enforcement - seeing that stated policy is carried out
Balance - keeping all parts of the system busy
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3.(30P) What are advantages and disadvantages of interrupting a non-preemtable device by OS? 
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It avoids possibility of deadlock, but the device cannot run correctly.
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