Locks turn out to be unnecessary for multithreaded code. A ringbuffer of messages is only slightly more complex, yet the gains are massive. Both in performance and simplicity.

It's possible to manage a ringbuffer without any locks. The trick is to have a counter for the producer thread, and a counter for each consumer thread. Whenever the producer wants to know "Is it safe to add a message?" it takes the minimum of all consumer counters, modulo the size of the ringbuffer. The result is the smallest index that the producer must not write beyond.

In other words, you always know when you're producing messages too quickly and need to wait on the consumers. And the consumers know when there's a message waiting -- they just look at the producer's counter. Blazingly fast, and no locks. Cool trick!