[PATCH] drm/ttm: once more fix ttm_bo_bulk_move_lru_tail

[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 at 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.


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