Cory Nelson wrote:
Comparing only the tag means that there is global counter incremented atomically. As a result a contention on this global counter may be encountered...
You should be able to use the exact same algos, but compare only the tag. No global counter needed.
I'm not understanding :-( Formally: Lets P is the set of all tagged pointer of our application. To resolve ABA-problem with cmp8xchg16 the following condition must be true: for each {p, q} from P: p.tag != q.tag p is struct { atomic64_t tag ; void * ptr ; }; Then, when we change tagged pointer p we must change its tag. How? Simply increment ++p.tag?.. In this case the condition may be violated... Another question: how the p.tag should be initialized. It seems, a global counter C appears: p.tag = atomic_inc( &C ) ; The global counter keeps the condition as true. Maybe, my reasoning is not true and you known best solution. Regards, Max