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

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nishimura at mxp

Nov 23, 2009, 11:28 PM

Post #1 of 3 (73 views)
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[BUGFIX][PATCH -stable] memcg: avoid oom-killing innocent task in case of use_hierarchy

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 [at] mxp>
---
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);
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index a7b2460..ed452e9 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -400,7 +400,7 @@ static int oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order,
cpuset_print_task_mems_allowed(current);
task_unlock(current);
dump_stack();
- mem_cgroup_print_oom_info(mem, current);
+ mem_cgroup_print_oom_info(mem, p);
show_mem();
if (sysctl_oom_dump_tasks)
dump_tasks(mem);
--
1.5.6.1

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kamezawa.hiroyu at jp

Nov 24, 2009, 4:00 PM

Post #2 of 3 (70 views)
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Re: [BUGFIX][PATCH -stable] memcg: avoid oom-killing innocent task in case of use_hierarchy [In reply to]

On Tue, 24 Nov 2009 16:28:54 +0900
Daisuke Nishimura <nishimura [at] mxp> 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 [at] mxp>
> ---
> 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 [at] jp>
(*) I'm sorry I can't work enough in these days.

Thanks,
-Kame

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balbir at linux

Nov 24, 2009, 8:08 PM

Post #3 of 3 (71 views)
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Re: [BUGFIX][PATCH -stable] memcg: avoid oom-killing innocent task in case of use_hierarchy [In reply to]

* nishimura [at] mxp <nishimura [at] mxp> [2009-11-24 16:28:54]:

> 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 [at] mxp>
> ---
> 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);
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> index a7b2460..ed452e9 100644
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -400,7 +400,7 @@ static int oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order,
> cpuset_print_task_mems_allowed(current);
> task_unlock(current);
> dump_stack();
> - mem_cgroup_print_oom_info(mem, current);
> + mem_cgroup_print_oom_info(mem, p);
> show_mem();
> if (sysctl_oom_dump_tasks)
> dump_tasks(mem);
>

Reviewed-by: Balbir Singh <balbir [at] linux>

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Balbir
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