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From: KOSAKI Motohiro on 16 Jun 2010 22:00
> On Wed, Jun 16, 2010 at 08:32:45PM +0900, KOSAKI Motohiro wrote:
> > When oom_kill_allocating_task is enabled, an argument of
> > oom_kill_process is not selected by select_bad_process(), but
> > just out_of_memory() caller task. It mean the task can be
> > unkillable. check it first.
> >
> > Signed-off-by: KOSAKI Motohiro <kosaki.motohiro(a)jp.fujitsu.com>
> > ---
> > mm/oom_kill.c | 11 +++++++++++
> > 1 files changed, 11 insertions(+), 0 deletions(-)
> >
> > diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> > index 6ca6cb8..3e48023 100644
> > --- a/mm/oom_kill.c
> > +++ b/mm/oom_kill.c
> > @@ -436,6 +436,17 @@ static int oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order,
> > unsigned long victim_points = 0;
> > struct timespec uptime;
> >
> > + /*
> > + * When oom_kill_allocating_task is enabled, p can be
> > + * unkillable. check it first.
> > + */
> > + if (is_global_init(p) || (p->flags & PF_KTHREAD))
> > + return 1;
> > + if (mem && !task_in_mem_cgroup(p, mem))
> > + return 1;
> > + if (!has_intersects_mems_allowed(p, nodemask))
> > + return 1;
> > +
>
> I think this check could be done before oom_kill_proces in case of
> sysctl_oom_kill_allocating_task, too.

ok.


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From: KOSAKI Motohiro on 21 Jun 2010 07:50
> On Thu, 17 Jun 2010, KOSAKI Motohiro wrote:
>
> > When oom_kill_allocating_task is enabled, an argument task of
> > oom_kill_process is not selected by select_bad_process(), It's
> > just out_of_memory() caller task. It mean the task can be
> > unkillable. check it first.
> >
>
> This should be unnecessary if oom_kill_process() appropriately returns
> non-zero when it cannot kill a task. What problem are you addressing with
> this fix?

oom_kill_process() only check its children are unkillable, not its own.
To add check oom_kill_process() also solve the issue. as my previous patch does.
but Minchan pointed out it's unnecessary. because when !oom_kill_allocating_task
case, we have the same check in select_bad_process().



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From: KOSAKI Motohiro on 30 Jun 2010 05:30
> On Mon, 21 Jun 2010, KOSAKI Motohiro wrote:
>
> > > > When oom_kill_allocating_task is enabled, an argument task of
> > > > oom_kill_process is not selected by select_bad_process(), It's
> > > > just out_of_memory() caller task. It mean the task can be
> > > > unkillable. check it first.
> > > >
> > >
> > > This should be unnecessary if oom_kill_process() appropriately returns
> > > non-zero when it cannot kill a task. What problem are you addressing with
> > > this fix?
> >
> > oom_kill_process() only check its children are unkillable, not its own.
>
> No, oom_kill_process() returns the value of oom_kill_task(victim) which is
> non-zero for !victim->mm in mmotm-2010-06-11-16-40 (and 2.6.34 although
> victim == p in that case).

oom_kill_task() only check OOM_DISABLE. and Minchan elaborated more detailed
concern. please see his mail.


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