On Mon, Jan 05, 2015 at 09:25:02PM -0500, Steven Rostedt wrote: > On Tue, 6 Jan 2015 10:32:47 +0900 > Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> wrote: > > > > > > +++ b/mm/slub.c > > > > @@ -2398,13 +2398,15 @@ redo: > > > > * reading from one cpu area. That does not matter as long > > > > * as we end up on the original cpu again when doing the cmpxchg. > > > > * > > > > - * Preemption is disabled for the retrieval of the tid because that > > > > - * must occur from the current processor. We cannot allow rescheduling > > > > - * on a different processor between the determination of the pointer > > > > - * and the retrieval of the tid. > > > > + * We should guarantee that tid and kmem_cache are retrieved on > > > > + * the same cpu. It could be different if CONFIG_PREEMPT so we need > > > > + * to check if it is matched or not. > > > > */ > > > > - 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(); > > > > > > Help maintenance more if barrier is documented in commit message. > > > > Hello, > > > > Okay. Will add some information about this barrier in commit message. > > A comment in the commit message is useless. Adding a small comment > above the barrier() call itself would be much more useful. Okay. Will do. 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>