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From: KAMEZAWA Hiroyuki on 15 Jun 2010 20:10
On Tue, 15 Jun 2010 18:59:25 +0900
Minchan Kim <minchan.kim(a)gmail.com> wrote:

> > -/*
> > +/**
> > + * find_lock_task_mm - Checking a process which a task belongs to has valid mm
> > + * and return a locked task which has a valid pointer to mm.
> > + *
>
> This comment should have been another patch.
> BTW, below comment uses "subthread" word.
> Personally it's easy to understand function's goal to me. :)
>
> How about following as?
> Checking a process which has any subthread with vaild mm
> ....
>
Sure. thank you. v2 is here. I removed unnecessary parts.

==
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu(a)jp.fujitsu.com>

When the OOM killer scans task, it check a task is under memcg or
not when it's called via memcg's context.

But, as Oleg pointed out, a thread group leader may have NULL ->mm
and task_in_mem_cgroup() may do wrong decision. We have to use
find_lock_task_mm() in memcg as generic OOM-Killer does.

Changelog:
- removed unnecessary changes in comments.

Cc: Oleg Nesterov <oleg(a)redhat.com>
Cc: Daisuke Nishimura <nishimura(a)mxp.nes.nec.co.jp>
Cc: Balbir Singh <balbir(a)linux.vnet.ibm.com>
Reviewed-by: Minchan Kim <minchan.kim(a)gmail.com>
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu(a)jp.fujitsu.com>
---
include/linux/oom.h | 2 ++
mm/memcontrol.c | 10 +++++++---
mm/oom_kill.c | 2 +-
3 files changed, 10 insertions(+), 4 deletions(-)

Index: mmotm-2.6.35-0611/include/linux/oom.h
===================================================================
--- mmotm-2.6.35-0611.orig/include/linux/oom.h
+++ mmotm-2.6.35-0611/include/linux/oom.h
@@ -45,6 +45,8 @@ static inline void oom_killer_enable(voi
oom_killer_disabled = false;
}

+extern struct task_struct *find_lock_task_mm(struct task_struct *p);
+
/* sysctls */
extern int sysctl_oom_dump_tasks;
extern int sysctl_oom_kill_allocating_task;
Index: mmotm-2.6.35-0611/mm/memcontrol.c
===================================================================
--- mmotm-2.6.35-0611.orig/mm/memcontrol.c
+++ mmotm-2.6.35-0611/mm/memcontrol.c
@@ -47,6 +47,7 @@
#include <linux/mm_inline.h>
#include <linux/page_cgroup.h>
#include <linux/cpu.h>
+#include <linux/oom.h>
#include "internal.h"

#include <asm/uaccess.h>
@@ -838,10 +839,13 @@ int task_in_mem_cgroup(struct task_struc
{
int ret;
struct mem_cgroup *curr = NULL;
+ struct task_struct *p;

- task_lock(task);
- curr = try_get_mem_cgroup_from_mm(task->mm);
- task_unlock(task);
+ p = find_lock_task_mm(task);
+ if (!p)
+ return 0;
+ curr = try_get_mem_cgroup_from_mm(p->mm);
+ task_unlock(p);
if (!curr)
return 0;
/*
Index: mmotm-2.6.35-0611/mm/oom_kill.c
===================================================================
--- mmotm-2.6.35-0611.orig/mm/oom_kill.c
+++ mmotm-2.6.35-0611/mm/oom_kill.c
@@ -87,7 +87,7 @@ static bool has_intersects_mems_allowed(
* pointer. Return p, or any of its subthreads with a valid ->mm, with
* task_lock() held.
*/
-static struct task_struct *find_lock_task_mm(struct task_struct *p)
+struct task_struct *find_lock_task_mm(struct task_struct *p)
{
struct task_struct *t = p;




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Prev: fs/ocfs2/dlm: Add missing spin_unlock
Next: [PATCH 1/1] module: initialize module dynamic debug later