On Tue, Jan 15, 2019 at 10:09:03PM +0100, Christoph Hellwig wrote: > On Wed, Jan 16, 2019 at 07:51:41AM +1100, Dave Chinner wrote: > > Atomic operations don't imply a memory barrier for dependent data, > > right? > > Documentation/atomic_t.txt says: > > -------------------------- snip -------------------------- > The rule of thumb: > > - non-RMW operations are unordered; > > - RMW operations that have no return value are unordered; > > - RMW operations that have a return value are fully ordered; > > [...] > > Fully ordered primitives are ordered against everything prior and everything > subsequent. Therefore a fully ordered primitive is like having an smp_mb() > before and an smp_mb() after the primitive. I guess I haven't looked at the documentation for a while. Or the implementation for that matter. /me goes off and looks. Oh, they are now implemented with built in, explicit smp_mb__before_atomic() and smp_mb__after_atomic() barriers. Ok, so the necessary barriers are there, my brain was telling me they still needed to be added manually and needed updating..... Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx
