[PATCH v3 09/13] mm/debug_vm_pgtable/locks: Move non page table modifying test together

[Anshuman Khandual]

On 09/01/2020 03:06 PM, Aneesh Kumar K.V wrote:
> 
>>>>
>>>> [   17.080644] ------------[ cut here ]------------
>>>> [   17.081342] kernel BUG at mm/pgtable-generic.c:164!
>>>> [   17.082091] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP
>>>> [   17.082977] Modules linked in:
>>>> [   17.083481] CPU: 79 PID: 1 Comm: swapper/0 Tainted: G        W         5.9.0-rc2-00105-g740e72cd6717 #14
>>>> [   17.084998] Hardware name: linux,dummy-virt (DT)
>>>> [   17.085745] pstate: 60400005 (nZCv daif +PAN -UAO BTYPE=--)
>>>> [   17.086645] pc : pgtable_trans_huge_deposit+0x58/0x60
>>>> [   17.087462] lr : debug_vm_pgtable+0x4dc/0x8f0
>>>> [   17.088168] sp : ffff80001219bcf0
>>>> [   17.088710] x29: ffff80001219bcf0 x28: ffff8000114ac000
>>>> [   17.089574] x27: ffff8000114ac000 x26: 0020000000000fd3
>>>> [   17.090431] x25: 0020000081400fd3 x24: fffffe00175c12c0
>>>> [   17.091286] x23: ffff0005df04d1a8 x22: 0000f18d6e035000
>>>> [   17.092143] x21: ffff0005dd790000 x20: ffff0005df18e1a8
>>>> [   17.093003] x19: ffff0005df04cb80 x18: 0000000000000014
>>>> [   17.093859] x17: 00000000b76667d0 x16: 00000000fd4e6611
>>>> [   17.094716] x15: 0000000000000001 x14: 0000000000000002
>>>> [   17.095572] x13: 000000000055d966 x12: fffffe001755e400
>>>> [   17.096429] x11: 0000000000000008 x10: ffff0005fcb6e210
>>>> [   17.097292] x9 : ffff0005fcb6e210 x8 : 0020000081590fd3
>>>> [   17.098149] x7 : ffff0005dd71e0c0 x6 : ffff0005df18e1a8
>>>> [   17.099006] x5 : 0020000081590fd3 x4 : 0020000081590fd3
>>>> [   17.099862] x3 : ffff0005df18e1a8 x2 : fffffe00175c12c0
>>>> [   17.100718] x1 : fffffe00175c1300 x0 : 0000000000000000
>>>> [   17.101583] Call trace:
>>>> [   17.101993]  pgtable_trans_huge_deposit+0x58/0x60
>>>> [   17.102754]  do_one_initcall+0x74/0x1cc
>>>> [   17.103381]  kernel_init_freeable+0x1d0/0x238
>>>> [   17.104089]  kernel_init+0x14/0x118
>>>> [   17.104658]  ret_from_fork+0x10/0x34
>>>> [   17.105251] Code: f9000443 f9000843 f9000822 d65f03c0 (d4210000)
>>>> [   17.106303] ---[ end trace e63471e00f8c147f ]---
>>>>
>>>
>>> IIUC, this should happen even without the series right? This is
>>>
>>>      assert_spin_locked(pmd_lockptr(mm, pmdp));
>>
>> Crash does not happen without this series. A previous patch [PATCH v3 08/13]
>> added pgtable_trans_huge_deposit/withdraw() in pmd_advanced_tests(). arm64
>> does not define __HAVE_ARCH_PGTABLE_DEPOSIT and hence falls back on generic
>> pgtable_trans_huge_deposit() which the asserts the lock.
>>
> 
> 
> I fixed that by moving the pgtable deposit after adding the pmd locks correctly.
> 
> mm/debug_vm_pgtable/locks: Move non page table modifying test together
> mm/debug_vm_pgtable/locks: Take correct page table lock
> mm/debug_vm_pgtable/thp: Use page table depost/withdraw with THP

Right, it does fix. But then both those patches should be folded/merged in
order to preserve git bisect ability, besides test classification reasons
as mentioned in a previous response and a possible redundant movement of
hugetlb_basic_tests().