How to achieve lock-free, but blocking behavior?

Question

I'm implementing a lock-free single producer single consumer queue for an intensive network application. I have a bunch of worker threads receiving work in their own separate queues, which they then dequeue and process.

Removing the locks from these queues have greatly improved the performance under high load, but they no longer block when the queues are empty, which in turn causes the CPU usage to skyrocket.

How can I efficiently cause a thread to block until it can successfully dequeue something or is killed/interrupted?

Answer 1

If you're on Linux, look into using a Futex. It provides the performance of a non-locking implementation by using atomic operations rather than kernel calls like a mutex would, but should you need to set the process to idle because of some condition not being true (i.e., lock-contention), it will then make the appropriate kernel calls to put the process to sleep and wake it back up at a future event. It's basically like a very fast semaphore.