Re: general protection fault in oom_unkillable_task

From: Tetsuo Handa
Date: Sat Jun 15 2019 - 12:57:51 EST


On 2019/06/16 1:11, 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.

While dump_tasks() traverses only each thread group, mem_cgroup_scan_tasks()
traverses each thread. To avoid printk()ing all threads in a thread group,
moving that check to

if (memcg && !task_in_mem_cgroup(p, memcg))
continue;

in dump_tasks() is better?

>
>>
>> /* p may not have freeable memory in nodemask */
>> if (!has_intersects_mems_allowed(p, nodemask))