Re: general protection fault in oom_unkillable_task

[Tetsuo Handa]

On 2019/06/17 15:33, Michal Hocko wrote:
> On Sat 15-06-19 09:11:37, Shakeel Butt wrote:
>> On Sat, Jun 15, 2019 at 6:50 AM Michal Hocko <mhocko@xxxxxxxxxx> wrote:
> [...]
>>> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
>>> index 5a58778c91d4..43eb479a5dc7 100644
>>> --- a/mm/oom_kill.c
>>> +++ b/mm/oom_kill.c
>>> @@ -161,8 +161,8 @@ static bool oom_unkillable_task(struct task_struct *p,
>>>                 return true;
>>>
>>>         /* When mem_cgroup_out_of_memory() and p is not member of the group */
>>> -       if (memcg && !task_in_mem_cgroup(p, memcg))
>>> -               return true;
>>> +       if (memcg)
>>> +               return false;
>>
>> This will break the dump_tasks() usage of oom_unkillable_task(). We
>> can change dump_tasks() to traverse processes like
>> mem_cgroup_scan_tasks() for memcg OOMs.
> 
> Right you are. Doing a similar trick to the oom victim selection is
> indeed better. We should really strive to not doing a global process
> iteration when we can do a targeted scan. Care to send a patch?

I posted a patch that (as a side effect) avoids oom_unkillable_task() from dump_tasks() at
https://lore.kernel.org/linux-mm/1558519686-16057-2-git-send-email-penguin-kernel@xxxxxxxxxxxxxxxxxxx/ .
What do you think?