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Unformatted text preview: ning immediately with null. The waiting thread needs to release its lock that it acquired when it entered the synchronized method and needs to reacquire it before trying again. In Java, this is implemented in the wait and notify methods. Similar primitives are available with POSIX threads (Pthreads) , and techniques for implementing this functionality with semaphores and other basic primitives can be found in . The changes that have been made from Figure 1 is highlighted with red boxes in Figure 3. We added to the put method a call to notifyAll. However, this implementation has a performance problem in that unnecessary notification will be sent even when there is no blocked thread. One way to handle this problem is to keep track of the number of blocked threads and only perform a notifyAll when the number is greater than zero. Figure 3. Blocking queue that ensures at most one thread can access the data structure (2‐3) More efficient concurrency‐control protocols: Note that the shared queue in Figure 1 o...
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This document was uploaded on 03/17/2014 for the course CS 4800 at Northeastern.
- Fall '12