August 2013 Archive


Semaphores
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Semaphores

This was the position in 1965, when E. W. Dijkstra (1965) suggested using an integer variable to count the number of wakeups saved for future use. In his suggestion, a new variable type, which he called a semaphore, was introduced. A semaphore could have the value 0,

Mutexes
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Mutexes

When the semaphore's ability to count is not required, a simplified version of the semaphore, called a mutex, is often used. Mutexes are good only for managing mutual exclusion to some shared resource or piece of code. They are easy and efficient to implement, which makes

Monitors
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Monitors

With semaphores and mutexes interprocess communication looks easy, right? Forget it. Look closely at the order of the downs before inserting or removing items from the buffer in Semaphores Figigure 1. Assume that the two downs in the producer's code were reversed in

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