Threadsafe FIFO Queue/Buffer

You should think about ConcurrentQueue, which is FIFO, in fact. If not suitable, try some of its relatives in Thread-Safe Collections. By using these you can avoid some risks.

You can actually handle this with the out-of-the-box BlockingCollection.

It is designed to have 1 or more producers, and 1 or more consumers. In your case, you would have multiple producers and one consumer.

When you receive a stop signal, have that signal handler

• Signal producer threads to stop
• Call CompleteAdding on the BlockingCollection instance

The consumer thread will continue to run until all queued items are removed and processed, then it will encounter the condition that the BlockingCollection is complete. When the thread encounters that condition, it just exits.