On 2024/12/17 20:54, Michal Hocko wrote:
> On Tue 17-12-24 12:18:28, Chen Ridong wrote:
> [...]
>> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
>> index 1c485beb0b93..14260381cccc 100644
>> --- a/mm/oom_kill.c
>> +++ b/mm/oom_kill.c
>> @@ -390,6 +390,7 @@ static int dump_task(struct task_struct *p, void *arg)
>> if (!is_memcg_oom(oc) && !oom_cpuset_eligible(p, oc))
>> return 0;
>>
>> + cond_resched();
>> task = find_lock_task_mm(p);
>> if (!task) {
>> /*
>
> This is called from RCU read lock for the global OOM killer path and I
> do not think you can schedule there. I do not remember specifics of task
> traversal for crgoup path but I guess that you might need to silence the
> soft lockup detector instead or come up with a different iteration
> scheme.
Thank you, Michal.
I made a mistake. I added cond_resched in the mem_cgroup_scan_tasks
function below the fn, but after reconsideration, it may cause
unnecessary scheduling for other callers of mem_cgroup_scan_tasks.
Therefore, I moved it into the dump_task function. However, I missed the
RCU lock from the global OOM.
I think we can use touch_nmi_watchdog in place of cond_resched, which
can silence the soft lockup detector. Do you think that is acceptable?
@@ -390,7 +391,7 @@ static int dump_task(struct task_struct *p, void *arg)
if (!is_memcg_oom(oc) && !oom_cpuset_eligible(p, oc))
return 0;
+ touch_nmi_watchdog();
task = find_lock_task_mm(p);
Best regards,
Ridong
