On Tue, 19 Feb 2019, Mikulas Patocka wrote: > > As I say, shouldn't the barrier be in `iowriteX' instead? I don't > > suppose these are allowed to be weakly ordered. > > > > Maciej > > iowriteX is for memory-mapped I/O, out[bwl] is for I/O ports. Well, actually `iowriteX' is generic and for MMIO you have `writeX'. See lib/iomap.c, the comment at the top and e.g. `iowrite8' there for an actual proof. Alpha may have an oddball implementation, but there you go. Drivers will assume they can do `iowriteX' to any kind of I/O resource, and ordering must be respected as per Documentation/memory-barriers.txt. Maciej
