On Wed, Aug 18, 2021 at 10:02:46PM +0800, Muchun Song wrote: > On Tue, Aug 17, 2021 at 9:43 AM Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote: > > > > + unsigned int target, nnodes; > > > > int i; > > > > int nid; > > > > + /* > > > > + * The barrier will stabilize the nodemask in a register or on > > > > + * the stack so that it will stop changing under the code. > > > > + * > > > > + * Between first_node() and next_node(), pol->nodes could be changed > > > > + * by other threads. So we put pol->nodes in a local stack. > > > > + */ > > > > + barrier(); > > > > I think this could be an smp_rmb()? > > Hi Matthew, > > I have a question. Why is barrier() not enough? I think barrier() may be more than is necessary. We don't need a barrier on non-SMP systems (or do we?) And we only need to order reads, not writes.
