On Wed, Jul 06, 2016 at 02:33:29PM +0900, Byungchul Park wrote: > On Wed, Jul 06, 2016 at 11:17:10AM +0900, Byungchul Park wrote: > > > > lock(A) > > wait_for(B) > > ~~~~~~~~~~~~~~~~~~~~~~~~ <- serialized by atomic operation > > lock(A) > > unlock(A) > > wake(B) > > unlock(A) > > By the way, I have a question. Is there anyone who could answer it? > > I want to serialize between two context's lock operations, for example, > > context A context B > -------------- -------------- > lock A > lock B ... > lock C > atomic_inc_return > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ <- serialization > atomic_read > lock D > ... lock E > lock F > > so that we can see these in the order like A -> B -> C -> D -> E -> F. > > atomic_inc_return() is used after lock C in context A, and atomic_read() > is used before lock D in context B. And I want to make it serialized when > the atomic_read() can see the increased value. > > Can I use smp_mb__after_atomic() just after atomic_read()
No. atomic_set() and atomic_read() are not RmW operations. > or should I use > smp_mb()? I think anyway I have to choose one of them for that ordering. smp_load_acquire(), if that observes the increment it will ensure D comes after etc.. Also, atomic_read() _could_ be enough, if its part of a control dependency, because LOCK very much involves a store, so the load->store order provided by the control dependency will already order things.
