Re: mm: swap: locking in release_pages()

From: Alexander Sverdlin
Date: Tue Apr 05 2022 - 16:17:39 EST

Hello Michal,

thanks for the quick reply!

On 05/04/2022 12:43, Michal Hocko wrote:
>> 1. Crash of v5.4.170 on an ARM32 machine:
>> Unable to handle kernel NULL pointer dereference at virtual address 00000104
>> pgd = e138149d
>> [00000104] *pgd=84d2fd003, *pmd=8ffd6f003
>> Internal error: Oops: a07 [#1] PREEMPT SMP ARM
>> ...
>> CPU: 1 PID: 6172 Comm: AaSysInfoRColle Tainted: G B O 5.4.170-... #1
>> Hardware name: Keystone
>> PC is at release_pages+0x194/0x358
>> LR is at release_pages+0x10c/0x358
> Which LOC does this correspond to? (faddr2line should give you a nice
> output).

Sorry, I forgot this info in the initial report:

this is indeed the del_page_from_lru_list() in this crash. So it's either two different ->lru_lock
or some other code path doesn't take lru_lock at all...

Best regards,
Alexander Sverdlin.