Re: [PATCH] debugobject: don't wake up kswapd from fill_pool()

[Tetsuo Handa]

On 2023/05/12 21:54, Thomas Gleixner wrote:
> On Fri, May 12 2023 at 19:57, Tetsuo Handa wrote:
>> On 2023/05/12 12:44, Andrew Morton wrote:
>>> On Thu, 11 May 2023 22:47:32 +0900 Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> wrote:
>>>
>>>> syzbot is reporting lockdep warning in fill_pool(), for GFP_ATOMIC is
>>>> (__GFP_HIGH | __GFP_KSWAPD_RECLAIM) which wakes up kswapd.
>>>> Since fill_pool() might be called with arbitrary locks held,
>>>> fill_pool() should not assume that holding pgdat->kswapd_wait is safe.
> 
> https://lore.kernel.org/lkml/871qjldbes.ffs@tglx/

.config says IS_ENABLED(CONFIG_PREEMPT_RT) == false, and lockdep says about
base->lock => pgdat->kswapd_wait => p->pi_lock => rq->__lock => base->lock
dependency but does not say about db->lock.

How can your patch fix this problem?