Lecture 13 Notes

Inthecodeisempty

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Unformatted text preview: situation is that tasks can be created dynamically and that UEs will terminate when they receive a special “poison pill" task. Then the appropriate behavior might be for the take operation on an empty queue to wait until the queue is nonempty, That is, we want a block‐on‐empty queue. The queue operations defined in Figure 1 is nonblocking queue, where it returns null if queue is empty. A straightforward implementation is to enforce mutual exclusion as described in Implementation Mechanisms. Note that we put synchronized keyword on the take and put methods, making them not to interleave each other. In the code, isEmpty method is private, and only invoked inside a synchronized method. Thus it need not be synchronized. (If it were public, it would need to be synchronized as well.) The blocking version of the shared queue is shown in Figure 3. In this version, the take operation is changed so that a thread trying to take from an empty queue will wait until it is filled rather than retur...
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