Re: [BUGFIX][PATCH -mmotm] memcg: avoid oom-killing innocent task in case of use_hierarchy

[Balbir Singh <balbir@linux.vnet.ibm.com>]

On Tue, Nov 24, 2009 at 11:27 AM, Daisuke Nishimura
<nishimura@mxp.nes.nec.co.jp> wrote:
> task_in_mem_cgroup(), which is called by select_bad_process() to check whether
> a task can be a candidate for being oom-killed from memcg's limit, checks
> "curr->use_hierarchy"("curr" is the mem_cgroup the task belongs to).
>
> But this check return true(it's false positive) when:
>
>        <some path>/00          use_hierarchy == 0      <- hitting limit
>          <some path>/00/aa     use_hierarchy == 1      <- "curr"
>
> This leads to killing an innocent task in 00/aa. This patch is a fix for this
> bug. And this patch also fixes the arg for mem_cgroup_print_oom_info(). We
> should print information of mem_cgroup which the task being killed, not current,
> belongs to.
>

Quick Question: What happens if <some path>/00 has no tasks in it
after your patches?

Balbir

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