Producer-consumer with sempahores

Question

Producer-consumer problem taken from Wikipedia:

semaphore mutex = 1
semaphore fillCount = 0
semaphore emptyCount = BUFFER_SIZE

procedure producer() {
    while (true) {
        item = produceItem()
        down(emptyCount)
            down(mutex)
                putItemIntoBuffer(item)
            up(mutex)
        up(fillCount)
    }
    up(fillCount) //the consumer may not finish before the producer.
}

procedure consumer() {
    while (true) {
        down(fillCount)
            down(mutex)
                item = removeItemFromBuffer()
            up(mutex)
        up(emptyCount)
        consumeItem(item)
    }
}

My question - why does the producer have up(fillCount) //the consumer may not finish before the producer after the while loop. When will the program get there and why is it needed?

Answer 1

I think the code doesn't make sense this way. The loop never ends, so the line in question can be never reached.

The code didn't originally contain that line, and it was added by an anonymous editor in March 2009. I removed that line now.

In general, code on Wikipedia is often edited by many people over a long period of time, so it's quite easy to introduce bugs into it.