Re: [PATCH 3/3] mm: memcontrol: add sanity checks for memcg->id.ref on get/put

[Michal Hocko]

On Mon 01-08-16 16:26:26, Vladimir Davydov wrote:
[...]
>  static struct mem_cgroup *mem_cgroup_id_get_active(struct mem_cgroup *memcg)
>  {
> -	while (!atomic_inc_not_zero(&memcg->id.ref))
> +	while (!atomic_inc_not_zero(&memcg->id.ref)) {
> +		VM_BUG_ON(mem_cgroup_is_root(memcg));
>  		memcg = parent_mem_cgroup(memcg);
> +	}

why is this BUG_ON ok? What if the root.use_hierarchy=true?

>  	return memcg;
>  }
-- 
Michal Hocko
SUSE Labs