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

[christophe leroy]

Le 29/06/2018 à 22:42, Larry Finger a écrit :
> My PowerBook G4 Aluminum crashes on boot with 4.18-rcX kernels with a 
> kernel BUG at include/linux/page-flags.h:700! The problem was bisected 
> to commit 1d40a5ea01d5 ("mm: mark pages in use for page tables"). It is 
> not possible to capture the bug with anything other than a camera. The 
> first few lines of the traceback are as follows:
> 
> free_pgd_range+0x19c/0x30c (unreliable)
> free_pgtables_0xa0/0xb0
> exit_pmap+0xf4/0x16c
> mmput+0x64/0xf0
> do_exit+0x33c/0x89c
> oops_end+0x13c/0x144
> _exception_pkey+0x58/0x128
> ret_from_except_full+0x0/0x4
> --- interrupt: 700 at free_pgd_range+0x19c/0x30c
>      LR = free_pgd_range+0x19c/0x30c
> free_pgtables+0xa/0xb
> exit_mnap+0xf4/0x16c
> mmput+0x64/0xf0
> flush_old_exec+0x490/0x550
> 
> 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.
> 

Oh, seems to be the one I noticed and told Aneesh about 
(https://patchwork.ozlabs.org/patch/922771/)

Aneesh provided the patch https://patchwork.ozlabs.org/patch/934111/ for 
it, does it help ?

Christophe

> Larry

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