[scott_s]

That depends on the synchronization mechanism used, and whether or not that mechanism is hooked into the kernel scheduler. Sometimes it is (such as pthread_mutex) and sometimes it is not (such as rolling your own spin locks).

[TickleSteve]

ok, any "sane" implementation would not use spin-locks for this purpose, but yes it is technically possible to do so.

Spin-locks are not really the mechanism of choice for this level of abstraction.