[the8472]

> but it does shoot down the cache line containing the lock in all cores other than the one that acquired the lock.

Well, as long as you do the test-CAS instead of the pure-CAS approach not every loop iteration results in cache line bouncing.

Plus intel has introduced the MWAIT[0] instruction to implement something similar to futex in hardware, i.e. the hyperthread can sleep until another core updates the cacheline in question.

[0] https://www.felixcloutier.com/x86/mwait

[atq2119]

That's true, though MWAIT can only be used from kernel mode. At least the docs say that you get a #UD exception if you attempt to use it from user mode.

[the8472]

Right, there's UMWAIT[0] for that, but that's quite new.

[0] https://www.felixcloutier.com/x86/umwait