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 realize you're only moving this code, but it would be good to fix that up while you're there.
