It's a reasonable question, because lock-free is a confusing term. Lock-free here does not mean "without any form of synchronization primitive". That is imposs

It's a reasonable question, because lock-free is a confusing term. Lock-free here does not mean "without any form of synchronization primitive". That is impossible. Some synchronization must occur. Instead, it is a term of art that means: 1. Thread failure can't cause other threads to get blocked. 2. Forward progress in the algorithm is guaranteed. Basically: threads can't block each other and death of threads does not screw things up. https://en.wikipedia.org/wiki/Non-blocking_algorithm https://en.wikipedia.org/wiki/Non-blocking_algorithm CPU atomics often work by blocking (they have to) but they are non-interruptible instructions and there is a fixed maximum execution time. (So you can still guarantee forward progress if you use them).