On Fri, Nov 12, 2010 at 02:35:59PM +0100, Johnny Billquist wrote: > Augh! And in which way would that improve things? Restarting > operations, as well as checking if they should be restarted will > hardly be cheaper than emulating CAS.
It is one way to emulate CAS. The price is loading the return address and doing a compare -- as opposed to masking interrupts in the CAS implementation at the omoment. > And while it is true that CAS is the common, and very popular, > low-level primitive in the litterature today, I fail to see the > relevance. When we talk about locks, we should be talking in terms > of acquiring and releasing the lock, not how it might be implemented > at a lower level. Atomic ops are used by other things as well like counter updates without mutexes. Things like lock-less lists can be implemented on top of CAS and the lock-less property is important as it makes it possible to use them from interrupt handlers etc. Joerg
