On Nov 16, 2010, at 9:10 AM, Alan Barrett wrote: > Please could somebody on the "eat your CAS whether you like it or not" > side of the fence explain why the following idea would not work: > > On Sat, 13 Nov 2010, der Mouse wrote: >> Consider this hypothetical: >> >> x86 does #define ATOMIC_OPS_USE_CAS and defines a CAS(); MI code >> notices this and defines all the higher-level primitives (if that's not >> too much of an oxymoron) in terms of CAS(). >> >> ppc, arm, all the arches sufficiently "modern" to have CAS, likewise. >> >> Arches without a sufficiently general CAS[%] do not define >> ATOMIC_OPS_USE_CAS and provides their own implementations of mutexes, >> spinlocks, whatever.
Because that flexibility already exists. A port can provide a full mutex or rwlock implementation or use the default based on CAS primitives. I think the question is about more about the naked use of atomic_cas_xxx which are scattered around in the kernel.
