Re: [PATCH v5 5/7] mm: rework non-root kmem_cache lifecycle management
From: Johannes Weiner
Date: Tue May 28 2019 - 18:07:21 EST
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.