On Wed, Jul 05, 2017 at 09:04:39AM -0700, Andy Lutomirski wrote: > On Wed, Jul 5, 2017 at 5:18 AM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote: > > On Thu, Jun 29, 2017 at 08:53:22AM -0700, Andy Lutomirski wrote: > >> @@ -104,18 +140,20 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next, > >> > >> /* Resume remote flushes and then read tlb_gen. */ > >> cpumask_set_cpu(cpu, mm_cpumask(next)); > > > > Barriers should have a comment... what is being ordered here against > > what? > > How's this comment? > > /* > * Resume remote flushes and then read tlb_gen. We need to do > * it in this order: any inc_mm_tlb_gen() caller that writes a > * larger tlb_gen than we read here must see our cpu set in > * mm_cpumask() so that it will know to flush us. The barrier > * here synchronizes with inc_mm_tlb_gen(). > */ Slightly confusing, you mean this, right? cpumask_set_cpu(cpu, mm_cpumask()); inc_mm_tlb_gen(); MB MB next_tlb_gen = atomic64_read(&next->context.tlb_gen); flush_tlb_others(mm_cpumask()); which seems to make sense. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
