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SubjectRe: [patch] mm, oom: prevent soft lockup on memcg oom for UP systems
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On 2020/03/11 7:55, David Rientjes wrote:
> On Wed, 11 Mar 2020, Tetsuo Handa wrote:
>
>>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>>> --- a/mm/vmscan.c
>>> +++ b/mm/vmscan.c
>>> @@ -2637,6 +2637,8 @@ static void shrink_node_memcgs(pg_data_t *pgdat, struct scan_control *sc)
>>> unsigned long reclaimed;
>>> unsigned long scanned;
>>>
>>> + cond_resched();
>>> +
>>
>> Is this safe for CONFIG_PREEMPTION case? If current thread has realtime priority,
>> can we guarantee that the OOM victim (well, the OOM reaper kernel thread rather
>> than the OOM victim ?) gets scheduled?
>>
>
> I think it's the best we can do that immediately solves the issue unless
> you have another idea in mind?

"schedule_timeout_killable(1) outside of oom_lock" or "the OOM reaper grabs oom_lock
so that allocating threads guarantee that the OOM reaper gets scheduled" or "direct OOM
reaping so that allocating threads guarantee that some memory is reclaimed".

>
>>> switch (mem_cgroup_protected(target_memcg, memcg)) {
>>> case MEMCG_PROT_MIN:
>>> /*
>>>
>>

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