[PATCH] drm/ttm: replace dma_resv object on deleted BOs v3

[Daniel Vetter]

On Tue, Feb 11, 2020 at 04:43:26PM +0100, Christian König wrote:
> When non-imported BOs are resurrected for delayed delete we replace
> the dma_resv object to allow for easy reclaiming of the resources.
> 
> v2: move that to ttm_bo_individualize_resv
> v3: add a comment to explain what's going on
> 
> Signed-off-by: Christian König <christian.koenig at amd.com>
> Reviewed-by: xinhui pan <xinhui.pan at amd.com>
> ---
>  drivers/gpu/drm/ttm/ttm_bo.c | 14 +++++++++++++-
>  1 file changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
> index bfc42a9e4fb4..8174603d390f 100644
> --- a/drivers/gpu/drm/ttm/ttm_bo.c
> +++ b/drivers/gpu/drm/ttm/ttm_bo.c
> @@ -393,6 +393,18 @@ static int ttm_bo_individualize_resv(struct ttm_buffer_object *bo)
>  
>  	r = dma_resv_copy_fences(&bo->base._resv, bo->base.resv);
>  	dma_resv_unlock(&bo->base._resv);
> +	if (r)
> +		return r;
> +
> +	if (bo->type != ttm_bo_type_sg) {
> +		/* This works because the BO is about to be destroyed and nobody
> +		 * reference it any more. The only tricky case is the trylock on
> +		 * the resv object while holding the lru_lock.
> +		 */

I'm foolish enough to believe this is correct :-)

Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>

> +		spin_lock(&ttm_bo_glob.lru_lock);
> +		bo->base.resv = &bo->base._resv;
> +		spin_unlock(&ttm_bo_glob.lru_lock);
> +	}
>  
>  	return r;
>  }
> @@ -724,7 +736,7 @@ static bool ttm_bo_evict_swapout_allowable(struct ttm_buffer_object *bo,
>  
>  	if (bo->base.resv == ctx->resv) {
>  		dma_resv_assert_held(bo->base.resv);
> -		if (ctx->flags & TTM_OPT_FLAG_ALLOW_RES_EVICT || bo->deleted)
> +		if (ctx->flags & TTM_OPT_FLAG_ALLOW_RES_EVICT)
>  			ret = true;
>  		*locked = false;
>  		if (busy)
> -- 
> 2.17.1
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch