[PATCH v2 1/2] drm/ttm: Fix a deadlock if the target BO is not idle during swap

[Pan, Xinhui]

[AMD Official Use Only]

It is the internal staging drm-next.

-----Original Message-----
From: Koenig, Christian <Christian.Koenig at amd.com>
Sent: 2021年9月6日 19:26
To: Pan, Xinhui <Xinhui.Pan at amd.com>; amd-gfx at lists.freedesktop.org
Cc: Deucher, Alexander <Alexander.Deucher at amd.com>; chenli at uniontech.com; dri-devel at lists.freedesktop.org
Subject: Re: [PATCH v2 1/2] drm/ttm: Fix a deadlock if the target BO is not idle during swap

Which branch is this patch based on? Please rebase on top drm-misc-fixes and resend.

Thanks,
Christian.

Am 06.09.21 um 03:12 schrieb xinhui pan:
> The ret value might be -EBUSY, caller will think lru lock is still
> locked but actually NOT. So return -ENOSPC instead. Otherwise we hit
> list corruption.
>
> ttm_bo_cleanup_refs might fail too if BO is not idle. If we return 0,
> caller(ttm_tt_populate -> ttm_global_swapout ->ttm_device_swapout)
> will be stuck as we actually did not free any BO memory. This usually
> happens when the fence is not signaled for a long time.
>
> Signed-off-by: xinhui pan <xinhui.pan at amd.com>
> Reviewed-by: Christian König <christian.koenig at amd.com>
> ---
>   drivers/gpu/drm/ttm/ttm_bo.c | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/ttm/ttm_bo.c
> b/drivers/gpu/drm/ttm/ttm_bo.c index 1fedd0eb67ba..f1367107925b 100644
> --- a/drivers/gpu/drm/ttm/ttm_bo.c
> +++ b/drivers/gpu/drm/ttm/ttm_bo.c
> @@ -1159,9 +1159,9 @@ int ttm_bo_swapout(struct ttm_buffer_object *bo, struct ttm_operation_ctx *ctx,
>       }
>
>       if (bo->deleted) {
> -             ttm_bo_cleanup_refs(bo, false, false, locked);
> +             ret = ttm_bo_cleanup_refs(bo, false, false, locked);
>               ttm_bo_put(bo);
> -             return 0;
> +             return ret == -EBUSY ? -ENOSPC : ret;
>       }
>
>       ttm_bo_move_to_pinned(bo);
> @@ -1215,7 +1215,7 @@ int ttm_bo_swapout(struct ttm_buffer_object *bo, struct ttm_operation_ctx *ctx,
>       if (locked)
>               dma_resv_unlock(bo->base.resv);
>       ttm_bo_put(bo);
> -     return ret;
> +     return ret == -EBUSY ? -ENOSPC : ret;
>   }
>
>   void ttm_bo_tt_destroy(struct ttm_buffer_object *bo)