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    <p>You would have to clarify what is it exactly that you want to achieve. For now the producers only increment an integer and the consumer decrements the value. This is not a very useful activity ;) I understand that this is only a test app, but still it is not clear enough what's the purpose of this processing, what are the constraints and so on.</p> <p>The producers produce some 'items'. The outcome of this production is represented as an integer value. 0 means no items, 1 means there is a pending item, that consumer can take. Is that right? Now, is it possible for the producer to produce several items before any of them gets consumed (incrementing the array cell to a value higher than 1)? Or does he have to wait for the last item to be consumed before the next one can be put into the storage? Is the storage limited or unlimited? If it is limited then is the limit shared among all the producers or is it defined per producer?</p> <blockquote> <p>What I was expecting was that, when a Producer updates its data, the Consumer immediately processes it i.e. after every Producer message there should be a Consumer message printed.</p> </blockquote> <p>Though it's not really clear what you want to achieve I will hold on to that quote and assume the following: there is a limit of 1 item per producer and the producer has to wait for the consumer to empty the storage before a new item can be put in the cell i.e. the only allowed values in the g_lDataArray are 0 and 1.</p> <p>To allow maximum concurrency between threads you will need a conditional variable/mutex pair for each cell of g_lDataArray (for each producer). You will also need a queue of updates that is a list of producers that have submitted their work and a conditional variable/mutex pair to guard it, this will replace g_lChangedProducerId which can only hold one value at a time.</p> <p>Every time a producer wants to put an item into the storage it has to acquire the respective lock, check if the storage is empty (g_lDataArray[lProducerId] == 0), if not wait on the condition variable and then, increment the cell, release the held lock, acquire the consumer lock, add his id to the update queue, notify the consumer, release the consumer lock. Of course if the producer would perform any real computations producing some real item, this work should be performed out of the scope of any lock, before the attempt to put the item in the storage.</p> <p>In pseudo code this looks like this:</p> <pre><code>// do some computations item = compute(); lock (mutexes[producerId]) { while (storage[producerId] != 0) wait(condVars[producerId]); storage[producerId] = item; } lock (consumerMutex) { queue.push(producerId); signal(consumerCondVar); } </code></pre> <p>The consumer should act as follows: acquire his lock, check if there are any pending updates to process, if not wait on the condition variable, take one update out of the queue (that is the number of the updating producer), acquire the lock for producer who's update is going to be processed, decrement the cell, notify the producer, release the producer's lock, release his lock, finally process the update.</p> <pre><code>lock (consumerMutex) { while (queue.isEmpty()) wait(consumerCondVar); producerId = queue.pop(); lock (mutexex[producerId]) { item = storage[producerId]; storage[producerId] = 0; signal(condVars[producerId]); } } //process the update process(item); </code></pre> <p>Hope this answer is what you needed.</p>
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