Re: [PATCH] drm/ttm: once more fix ttm_bo_bulk_move_lru_tail

["Michel Dänzer" <michel@daenzer.net>]

On 2018-09-13 10:55 a.m., Christian König wrote:
> Am 13.09.2018 um 10:35 schrieb Michel Dänzer:
>> [ Moving to dri-devel, where TTM patches are reviewed ]
>>
>> On 2018-09-12 9:23 p.m., 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.
>>>
>>> Signed-off-by: Christian König <christian.koenig@amd.com>
>>> ---
>>>   drivers/gpu/drm/ttm/ttm_bo.c | 51
>>> ++++++++++++++++++++++++++------------------
>>>   1 file changed, 30 insertions(+), 21 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
>>> index 138c98902033..b2a33bf1ef10 100644
>>> --- a/drivers/gpu/drm/ttm/ttm_bo.c
>>> +++ b/drivers/gpu/drm/ttm/ttm_bo.c
>>> @@ -247,23 +247,18 @@ void ttm_bo_move_to_lru_tail(struct
>>> ttm_buffer_object *bo,
>>>   }
>>>   EXPORT_SYMBOL(ttm_bo_move_to_lru_tail);
>>>   -static void ttm_bo_bulk_move_helper(struct ttm_lru_bulk_move_pos
>>> *pos,
>>> -                    struct list_head *lru, bool is_swap)
>>> +static void ttm_list_move_bulk_tail(struct list_head *list,
>>> +                    struct list_head *first,
>>> +                    struct list_head *last)
>>>   {
>>> -    struct list_head *list;
>>> -    LIST_HEAD(entries);
>>> -    LIST_HEAD(before);
>>> +    first->prev->next = last->next;
>>> +    last->next->prev = first->prev;
>>>   -    reservation_object_assert_held(pos->last->resv);
>>> -    list = is_swap ? &pos->last->swap : &pos->last->lru;
>>> -    list_cut_position(&entries, lru, list);
>>> +    list->prev->next = first;
>>> +    first->prev = list->prev;
>>>   -    reservation_object_assert_held(pos->first->resv);
>>> -    list = is_swap ? pos->first->swap.prev : pos->first->lru.prev;
>>> -    list_cut_position(&before, &entries, list);
>>> -
>>> -    list_splice(&before, lru);
>>> -    list_splice_tail(&entries, lru);
>>> +    last->next = list;
>>> +    list->prev = last;
>>>   }
>>>     void ttm_bo_bulk_move_lru_tail(struct ttm_lru_bulk_move *bulk)
>>> @@ -271,23 +266,33 @@ void ttm_bo_bulk_move_lru_tail(struct
>>> ttm_lru_bulk_move *bulk)
>>>       unsigned i;
>>>         for (i = 0; i < TTM_MAX_BO_PRIORITY; ++i) {
>>> +        struct ttm_lru_bulk_move_pos *pos = &bulk->tt[i];
>>>           struct ttm_mem_type_manager *man;
>>>   -        if (!bulk->tt[i].first)
>>> +        if (!pos->first)
>>>               continue;
>>>   -        man = &bulk->tt[i].first->bdev->man[TTM_PL_TT];
>>> -        ttm_bo_bulk_move_helper(&bulk->tt[i], &man->lru[i], false);
>>> +        reservation_object_assert_held(pos->first->resv);
>>> +        reservation_object_assert_held(pos->last->resv);
>>> +
>>> +        man = &pos->first->bdev->man[TTM_PL_TT];
>>> +        ttm_list_move_bulk_tail(&man->lru[i], &pos->first->lru,
>>> +                    &pos->last->lru);
>>>       }
>>>         for (i = 0; i < TTM_MAX_BO_PRIORITY; ++i) {
>>> +        struct ttm_lru_bulk_move_pos *pos = &bulk->vram[i];
>>>           struct ttm_mem_type_manager *man;
>>>   -        if (!bulk->vram[i].first)
>>> +        if (!pos->first)
>>>               continue;
>>>   -        man = &bulk->vram[i].first->bdev->man[TTM_PL_VRAM];
>>> -        ttm_bo_bulk_move_helper(&bulk->vram[i], &man->lru[i], false);
>>> +        reservation_object_assert_held(pos->first->resv);
>>> +        reservation_object_assert_held(pos->last->resv);
>>> +
>>> +        man = &pos->first->bdev->man[TTM_PL_VRAM];
>>> +        ttm_list_move_bulk_tail(&man->lru[i], &pos->first->lru,
>>> +                    &pos->last->lru);
>>>       }
>>>         for (i = 0; i < TTM_MAX_BO_PRIORITY; ++i) {
>>> @@ -297,8 +302,12 @@ void ttm_bo_bulk_move_lru_tail(struct
>>> ttm_lru_bulk_move *bulk)
>>>           if (!pos->first)
>>>               continue;
>>>   +        reservation_object_assert_held(pos->first->resv);
>>> +        reservation_object_assert_held(pos->last->resv);
>>> +
>>>           lru = &pos->first->bdev->glob->swap_lru[i];
>>> -        ttm_bo_bulk_move_helper(&bulk->swap[i], lru, true);
>>> +        ttm_list_move_bulk_tail(lru, &pos->first->swap,
>>> +                    &pos->last->swap);
>>>       }
>>>   }
>>>   EXPORT_SYMBOL(ttm_bo_bulk_move_lru_tail);
>>>
>> Seems like more code could be kept in / moved into the shared helper
>> function. That would keep the ttm_bo_bulk_move_lru_tail code leaner, and
>> might make the helper function changes easier to review as well.
> 
> Yeah, actually only wanted to send that to Rui and you for testing.
> 
> Going to clean that up and send it for upstream review today.

Sounds good, but Tom needs to test it as well.


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