On Tue, May 28, 2019 at 06:03:53PM -0400, Johannes Weiner wrote: > On Tue, May 21, 2019 at 01:07:33PM -0700, Roman Gushchin wrote: > > + arr = rcu_dereference(cachep->memcg_params.memcg_caches); > > + > > + /* > > + * Make sure we will access the up-to-date value. The code updating > > + * memcg_caches issues a write barrier to match this (see > > + * memcg_create_kmem_cache()). > > + */ > > + memcg_cachep = READ_ONCE(arr->entries[kmemcg_id]); > > READ_ONCE() isn't an SMP barrier, it just prevents compiler > muckery. This needs an explicit smp_rmb() to pair with the smp_wmb() > on the other side.
I believe rcu_dereference()/rcu_assign_pointer()/... are better replacements. > > I realize you're only moving this code, but it would be good to fix > that up while you're there. Right. I'll try to fix it with new-ish rcu API in a separate patch preceding this one. Thank you for looking into the series!
