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

[Alex Deucher <alexdeucher-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

On Wed, Sep 12, 2018 at 3:25 PM Christian König
<ckoenig.leichtzumerken@gmail.com> 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>

Acked-by: Alex Deucher <alexander.deucher@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);
> --
> 2.14.1
>
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