Actually I didn't claim that lock-free is more efficient - I explicitly said that it isn't necessarily more efficient, though I didn't discuss the reasons that

Actually I didn't claim that lock-free is more efficient - I explicitly said that it isn't necessarily more efficient, though I didn't discuss the reasons that you do discuss; I only said that "lock-based" is defined by the need to deal with blocking upon suspension - not that it's necessarily a bad property in any way, in particular in its efficiency impacts.