Re: [PATCH 1/3] memcg: oom wakeup filter

Andrew Morton
2010-03-15T21:50:49Z

On Fri, 12 Mar 2010 14:31:37 +0900
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:

> +static int memcg_oom_wake_function(wait_queue_t *wait,
> + unsigned mode, int sync, void *arg)
> +{
> + struct mem_cgroup *wake_mem = (struct mem_cgroup *)arg;
> + struct oom_wait_info *oom_wait_info;
> +
> + /* both of oom_wait_info->mem and wake_mem are stable under us */
> + oom_wait_info = container_of(wait, struct oom_wait_info, wait);
> +
> + if (oom_wait_info->mem == wake_mem)
> + goto wakeup;
> + /* if no hierarchy, no match */
> + if (!oom_wait_info->mem->use_hierarchy || !wake_mem->use_hierarchy)
> + return 0;
> + /* check hierarchy */
> + if (!css_is_ancestor(&oom_wait_info->mem->css, &wake_mem->css) &&
> + !css_is_ancestor(&wake_mem->css, &oom_wait_info->mem->css))
> + return 0;
> +
> +wakeup:
> + return autoremove_wake_function(wait, mode, sync, arg);
> +}

What are the locking rules for calling css_is_ancestor()?