This is how it should be. IIRC -- apologies, can't find a source --, Ulrich Drepper wrote somewhere about NPTL that its mutexes were not particularly lightweigh

This is how it should be. IIRC -- apologies, can't find a source --, Ulrich Drepper wrote somewhere about NPTL that its mutexes were not particularly lightweight, but that you should design your program for low contention anyways. For highly contended data structures, spinlocks (and nowadays explicit atomics) are likely better.