[Question] race condition in mm/page_alloc.c regarding page->lru?

[TAO HU]

Hi, kamezawa hiroyu

Thanks for the hint!

Hi, Minchan Kim

Sorry. Not exactly sure your idea about <grep "page handling">.
Below is a result of $ grep -n -r "list_del(&page->lru)" * in our src tree

arch/s390/mm/pgtable.c:83:	list_del(&page->lru);
arch/s390/mm/pgtable.c:226:		list_del(&page->lru);
arch/x86/mm/pgtable.c:60:	list_del(&page->lru);
drivers/xen/balloon.c:154:	list_del(&page->lru);
drivers/virtio/virtio_balloon.c:143:		list_del(&page->lru);
fs/cifs/file.c:1780:		list_del(&page->lru);
fs/btrfs/extent_io.c:2584:		list_del(&page->lru);
fs/mpage.c:388:		list_del(&page->lru);
include/linux/mm_inline.h:37:	list_del(&page->lru);
include/linux/mm_inline.h:47:	list_del(&page->lru);
kernel/kexec.c:391:		list_del(&page->lru);
kernel/kexec.c:711:			list_del(&page->lru);
mm/migrate.c:69:		list_del(&page->lru);
mm/migrate.c:695: 		list_del(&page->lru);
mm/hugetlb.c:467:			list_del(&page->lru);
mm/hugetlb.c:509:			list_del(&page->lru);
mm/hugetlb.c:836:		list_del(&page->lru);
mm/hugetlb.c:844:			list_del(&page->lru);
mm/hugetlb.c:900:			list_del(&page->lru);
mm/hugetlb.c:1130:			list_del(&page->lru);
mm/hugetlb.c:1809:		list_del(&page->lru);
mm/vmscan.c:597:		list_del(&page->lru);
mm/vmscan.c:1148:			list_del(&page->lru);
mm/vmscan.c:1246:		list_del(&page->lru);
mm/slub.c:827:	list_del(&page->lru);
mm/slub.c:1249:	list_del(&page->lru);
mm/slub.c:1263:		list_del(&page->lru);
mm/slub.c:2419:			list_del(&page->lru);
mm/slub.c:2809:				list_del(&page->lru);
mm/readahead.c:65:		list_del(&page->lru);
mm/readahead.c:100:		list_del(&page->lru);
mm/page_alloc.c:532:		list_del(&page->lru);
mm/page_alloc.c:679:		list_del(&page->lru);
mm/page_alloc.c:741:		list_del(&page->lru);
mm/page_alloc.c:820:			list_del(&page->lru);
mm/page_alloc.c:1107:		list_del(&page->lru);
mm/page_alloc.c:4784:		list_del(&page->lru);

On Fri, Apr 2, 2010 at 1:15 PM, Minchan Kim <minchan.kim at gmail.com> wrote:
> On Fri, Apr 2, 2010 at 2:04 PM, KAMEZAWA Hiroyuki
> <kamezawa.hiroyu at jp.fujitsu.com> wrote:
>> On Fri, 2 Apr 2010 11:51:33 +0800
>> TAO HU <tghk48 at motorola.com> wrote:
>>
>>> 2 patches related to page_alloc.c were applied.
>>> Does anyone see a connection between the 2 patches and the panic?
>>> NOTE: the full patches are attached.
>>>
>>
>> I don't think there are relationship between patches and your panic.
>>
>> BTW, there is other case about the backlog rather than race in alloc_pages()
>> itself. If someone list_del(&page->lru) and the page is already freed,
>> you'll see the same backlog later.
>> Then, I doubt use-after-free case rather than complicated races.
>
> It does make sense.
> Please, grep "page handling" by out-of-mainline code.
> If you found out, Please, post it.
>
> --
> Kind regards,
> Minchan Kim
>