[PATCH] drm/ttm: fix kref count mess in ttm_bo_move_to_lru_tail

[Alex Deucher]

Ping.  Any objections?


On Wed, Apr 20, 2016 at 1:52 PM, Alex Deucher <alexdeucher at gmail.com> wrote:
> From: Flora Cui <Flora.Cui at amd.com>
>
> Fixes the following scenario:
>
> 1. Page table bo allocated in vram and linked to man->lru.
>    tbo->list_kref.refcount=2
> 2. Page table bo is swapped out and removed from man->lru.
>    tbo->list_kref.refcount=1
> 3. Command submission from userspace.  Page table bo is moved
>    to vram.  ttm_bo_move_to_lru_tail() link it to man->lru and
>    don't increase the kref count.
>
> Signed-off-by: Flora Cui <Flora.Cui at amd.com>
> Reviewed-by: Christian König <christian.koenig at amd.com>
> Signed-off-by: Alex Deucher <alexander.deucher at amd.com>
> Cc: stable at vger.kernel.org
> ---
>  drivers/gpu/drm/ttm/ttm_bo.c | 17 ++++-------------
>  1 file changed, 4 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
> index 4cbf265..e3daafa 100644
> --- a/drivers/gpu/drm/ttm/ttm_bo.c
> +++ b/drivers/gpu/drm/ttm/ttm_bo.c
> @@ -230,22 +230,13 @@ EXPORT_SYMBOL(ttm_bo_del_sub_from_lru);
>
>  void ttm_bo_move_to_lru_tail(struct ttm_buffer_object *bo)
>  {
> -       struct ttm_bo_device *bdev = bo->bdev;
> -       struct ttm_mem_type_manager *man;
> +       int put_count = 0;
>
>         lockdep_assert_held(&bo->resv->lock.base);
>
> -       if (bo->mem.placement & TTM_PL_FLAG_NO_EVICT) {
> -               list_del_init(&bo->swap);
> -               list_del_init(&bo->lru);
> -
> -       } else {
> -               if (bo->ttm && !(bo->ttm->page_flags & TTM_PAGE_FLAG_SG))
> -                       list_move_tail(&bo->swap, &bo->glob->swap_lru);
> -
> -               man = &bdev->man[bo->mem.mem_type];
> -               list_move_tail(&bo->lru, &man->lru);
> -       }
> +       put_count = ttm_bo_del_from_lru(bo);
> +       ttm_bo_list_ref_sub(bo, put_count, true);
> +       ttm_bo_add_to_lru(bo);
>  }
>  EXPORT_SYMBOL(ttm_bo_move_to_lru_tail);
>
> --
> 2.5.5
>