If you can reduce everything to _one_ mutex, that's simple. As soon as you have two mutexes, you need to start worrying whether one thread grabs A then B and a

If you can reduce everything to _one_ mutex, that's simple. As soon as you have two mutexes, you need to start worrying whether one thread grabs A then B and another grabs B then A. In larger projects with multiple people contributing, the mutex and condvar approach does not scale well. It's very easy to get difficult to reproduce race conditions.