Re: [PATCH V14] mm/debug: Add tests validating architecture page table helpers

Christophe Leroy
2020-03-04T06:49:06Z

Le 04/03/2020 à 02:39, Qian Cai a écrit :
>
>> Below is slightly modified version of your change above and should still
>> prevent the bug on powerpc. Will it be possible for you to re-test this
>> ? Once confirmed, will send a patch enabling this test on powerpc64
>> keeping your authorship. Thank you.
>
> This works fine on radix MMU but I decided to go a bit future to test hash
> MMU. The kernel will stuck here below. I did confirm that pte_alloc_map_lock()
> was successful, so I don’t understand hash MMU well enough to tell why
> it could still take an interrupt at pte_clear_tests() even before we calls
> pte_unmap_unlock()?

AFAIU, you are not taking an interrupt here. You are stuck in the
pte_update(), most likely due to nested locks. Try with LOCKDEP ?

Christophe

>
> [ 33.881515][ T1] ok 8 - property-entry
> [ 33.883653][ T1] debug_vm_pgtable: debug_vm_pgtable: Validating
> architecture page table helpers
> [ 60.418885][ C8] watchdog: BUG: soft lockup - CPU#8 stuck for 23s!
> [swapper/0:1]