On Mon, Jan 05, 2015 at 07:03:12PM -0800, Davidlohr Bueso wrote: > On Mon, 2015-01-05 at 10:36 +0900, Joonsoo Kim wrote: > > - preempt_disable(); > > - c = this_cpu_ptr(s->cpu_slab); > > + do { > > + tid = this_cpu_read(s->cpu_slab->tid); > > + c = this_cpu_ptr(s->cpu_slab); > > + } while (IS_ENABLED(CONFIG_PREEMPT) && unlikely(tid != c->tid)); > > + barrier(); > > I don't see the compiler reodering the object/page stores below, since c > is updated in the loop anyway. Is this really necessary (same goes for > slab_free)? The generated code by gcc 4.8 looks correct without it. > Additionally, the implied barriers for preemption control aren't really > the same semantics used here (if that is actually the reason why you are > using them). Hello, I'd like to use tid as a pivot so it should be fetched before fetching anything on c. Is it impossible even if !CONFIG_PREEMPT without barrier()? Thanks. -- 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>