On Tue, 27 Jun 2023, Jason Gunthorpe wrote: > On Wed, Jun 21, 2023 at 07:36:11PM -0700, Hugh Dickins wrote: > > [PATCH v3 05/12] powerpc: add pte_free_defer() for pgtables sharing page ... > Yes, this makes sense to me, very simple.. > > I always for get these details but atomic_dec_and_test() is a release? > So the SetPageActive is guarenteed to be visible in another thread > that reaches 0? Yes, that's my understanding - so the TestClearPageActive adds more to the guarantee than is actually needed. "release": you speak the modern language, whereas I haven't advanced from olden-days barriers: atomic_dec_and_test() meets atomic_t.txt's - RMW operations that have a return value are fully ordered; which a quick skim of present-day memory-barriers.txt suggests would imply both ACQUIRE and RELEASE. Please correct me if I'm mistaken! Hugh
