In our working producer and consumer solutions with a single buffer slot using condition variables, we used two condition variables. Why was the second condition variable necessary?

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One condition variable is needed to wake any sleeping threads up and the other is needed to put any threads that need to wait to sleep. With only one condition variable, threads could only sleep or try and wake things up, but not both and therefore our code would be very broken.

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One condition variable was used as a lock around the critical section, so without the second condition variable we would not have mutual exclusion and therefore have race conditions.

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Two conditions variables were only needed when checking  count  with an if statement. When using a while loop, a single condition variable is sufficient.

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With only a single condition variable, it might be the case that consumers wake up other consumers and producers wake up other consumers. This can lead to all threads sleeping forever.

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In our working producer and consumer solutions with a single buffer slot using c...

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