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Lecture 13 Notes

Compared to the nonblocking queue this scheme

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Unformatted text preview: that uses separate locks so they can proceed concurrently (2‐3) Nested locks for blocking queue: It is tricky to implement a blocking queue based on the queue that uses separate locks for the take and put method. The trickiness comes from the fact that wait, notify, notifyAll methods on an object can only be invoked within a block synchronized on that object. Also, if we have optimized the invocations of notify as described before then w, the count of waiting threads, would be accessed in both put and take. Therefore, we use putLock both to protect w and to serve as the lock on which a taking thread blocks when the queue is empty. Figure 5. Blocking shared queue that uses separate nested locks Code is shown in Figure 5. Notice that putLock.wait() in take will release only the lock on putLock, so a blocked thread will continue to block other takers from the outer block synchronized on takeLock. This is okay for this particular problem. Compared to the nonblocking queue, this scheme c...
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