[PATCH] drm/ttm: once more fix ttm_bo_bulk_move_lru_tail

[Michel Dänzer]

On 2018-09-14 10:22 a.m., Huang Rui wrote:
> On Thu, Sep 13, 2018 at 07:32:24PM +0800, Christian König wrote:
>> Am 13.09.2018 um 10:31 schrieb Huang Rui:
>>> On Wed, Sep 12, 2018 at 09:23:55PM +0200, Christian König wrote:
>>>> While cutting the lists we sometimes accidentally added a list_head from
>>>> the stack to the LRUs, effectively corrupting the list.
>>>>
>>>> Remove the list cutting and use explicit list manipulation instead.
>>> This patch actually fixes the corruption bug. Was it a defect of
>>> list_cut_position or list_splice handlers?
>>
>> We somehow did something illegal with list_cut_position. I haven't 
>> narrowed it down till the end, but we ended up with list_heads from the 
>> stack to the lru.
> 
> I am confused, in theory, even we do any manipulation with list helper, it
> should not trigger the list corruption. The usage of those helpers should
> ensure the list operation safely...

There's nothing the helpers can do about being passed in pointers to
stack memory. It's a bug in the code using the helpers.


-- 
Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer