[Update] Regression in 4.18 - 32-bit PowerPC crashes on boot - bisected to commit 1d40a5ea01d5

Larry Finger Larry.Finger at lwfinger.net
Tue Jul 3 06:51:03 AEST 2018

On 07/01/2018 11:16 PM, Michael Ellerman wrote:
> Linus Torvalds <torvalds at linux-foundation.org> writes:
>> On Fri, Jun 29, 2018 at 1:42 PM Larry Finger <Larry.Finger at lwfinger.net> wrote:
>>> I have more information regarding this BUG. Line 700 of page-flags.h is the
>>> macro PAGE_TYPE_OPS(Table, table). For further debugging, I manually expanded
>>> the macro, and found that the bug line is VM_BUG_ON_PAGE(!PageTable(page), page)
>>> in routine __ClearPageTable(), which is called from pgtable_page_dtor() in
>>> include/linux/mm.h. I also added a printk call to PageTable() that logs
>>> page->page_type. The routine was called twice. The first had page_type of
>>> 0xfffffbff, which would have been expected for a . The second call had
>>> 0xffffffff, which led to the BUG.
>> So it looks to me like the tear-down of the page tables first found a
>> page that is indeed a page table, and cleared the page table bit
>> (well, it set it - the bits are reversed).
> ...
>> That said, can some ppc person who knows the 32-bit ppc code and maybe
>> knows what that "interrupt: 700" means talk about that oddity in the
>> trace, please?
> I think everyone else answered your questions here, and it should be
> fixed now in your tree.
> Larry let me know if you're still seeing a crash with 4.18-rc3.

The problem is fixed in 4.18-rc3. Thanks to all that helped.


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