Re: [-mm patch] Show memcg information during OOM (v3)

[Li Zefan <lizf@cn.fujitsu.com>]

> +	mem_cgrp = memcg->css.cgroup;
> +	task_cgrp = mem_cgroup_from_task(p)->css.cgroup;

I just noticed since v2, task's cgroup is also printed. Then 2 issues here:

1. this is better: task_cgrp = task_subsys_state(p, mem_cgroup_subsys_id);
2. getting cgroup from a task should be protected by task_lock or rcu_read_lock,
   so we can put the above statement inside rcu_read_lock below.

> +
> +	rcu_read_lock();
> +	ret = cgroup_path(task_cgrp, task_memcg_name, PATH_MAX);
> +	if (ret < 0) {
> +		/*
> +		 * Unfortunately, we are unable to convert to a useful name
> +		 * But we'll still print out the usage information
> +		 */
> +		rcu_read_unlock();
> +		goto done;
> +	}
> +	ret = cgroup_path(mem_cgrp, memcg_name, PATH_MAX);
> +	 if (ret < 0) {
> +		rcu_read_unlock();
> +		goto done;
> +	}
> +
> +	rcu_read_unlock();

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