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SubjectRe: [BUGFIX][PATCH -stable] memcg: avoid oom-killing innocent task in case of use_hierarchy
On Tue, 24 Nov 2009 16:28:54 +0900
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.
>
> Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
> ---
> mm/memcontrol.c | 2 +-
> mm/oom_kill.c | 2 +-
> 2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index fd4529d..3acc226 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -496,7 +496,7 @@ int task_in_mem_cgroup(struct task_struct *task, const struct mem_cgroup *mem)
> task_unlock(task);
> if (!curr)
> return 0;
> - if (curr->use_hierarchy)
> + if (mem->use_hierarchy)
> ret = css_is_ancestor(&curr->css, &mem->css);
> else
> ret = (curr == mem);

Hmm. Maybe not-expected behavior...could you add comment ?

Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
(*) I'm sorry I can't work enough in these days.

Thanks,
-Kame



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