Re: [PATCH v4 16/21] dma-buf: Move dma_buf_attach() to dynamic locking specification

[Christian König <christian.koenig@xxxxxxx>]

Am 31.08.22 um 17:37 schrieb Dmitry Osipenko:
> Move dma-buf attachment API functions to the dynamic locking specification
> by taking the reservation lock around the mapping operations. The strict
> locking convention prevents deadlock situations for dma-buf importers and
> exporters.
>
> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@xxxxxxxxxxxxx>

Reviewed-by: Christian König <christian.koenig@xxxxxxx>

> ---
>   drivers/dma-buf/dma-buf.c | 20 ++++++++------------
>   1 file changed, 8 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
> index ceea4839c641..073942bf5ae9 100644
> --- a/drivers/dma-buf/dma-buf.c
> +++ b/drivers/dma-buf/dma-buf.c
> @@ -858,8 +858,8 @@ dma_buf_dynamic_attach(struct dma_buf *dmabuf, struct device *dev,
>   	    dma_buf_is_dynamic(dmabuf)) {
>   		struct sg_table *sgt;
>   
> +		dma_resv_lock(attach->dmabuf->resv, NULL);
>   		if (dma_buf_is_dynamic(attach->dmabuf)) {
> -			dma_resv_lock(attach->dmabuf->resv, NULL);
>   			ret = dmabuf->ops->pin(attach);
>   			if (ret)
>   				goto err_unlock;
> @@ -872,8 +872,7 @@ dma_buf_dynamic_attach(struct dma_buf *dmabuf, struct device *dev,
>   			ret = PTR_ERR(sgt);
>   			goto err_unpin;
>   		}
> -		if (dma_buf_is_dynamic(attach->dmabuf))
> -			dma_resv_unlock(attach->dmabuf->resv);
> +		dma_resv_unlock(attach->dmabuf->resv);
>   		attach->sgt = sgt;
>   		attach->dir = DMA_BIDIRECTIONAL;
>   	}
> @@ -889,8 +888,7 @@ dma_buf_dynamic_attach(struct dma_buf *dmabuf, struct device *dev,
>   		dmabuf->ops->unpin(attach);
>   
>   err_unlock:
> -	if (dma_buf_is_dynamic(attach->dmabuf))
> -		dma_resv_unlock(attach->dmabuf->resv);
> +	dma_resv_unlock(attach->dmabuf->resv);
>   
>   	dma_buf_detach(dmabuf, attach);
>   	return ERR_PTR(ret);
> @@ -936,21 +934,19 @@ void dma_buf_detach(struct dma_buf *dmabuf, struct dma_buf_attachment *attach)
>   	if (WARN_ON(!dmabuf || !attach))
>   		return;
>   
> +	dma_resv_lock(attach->dmabuf->resv, NULL);
> +
>   	if (attach->sgt) {
> -		if (dma_buf_is_dynamic(attach->dmabuf))
> -			dma_resv_lock(attach->dmabuf->resv, NULL);
>   
>   		__unmap_dma_buf(attach, attach->sgt, attach->dir);
>   
> -		if (dma_buf_is_dynamic(attach->dmabuf)) {
> +		if (dma_buf_is_dynamic(attach->dmabuf))
>   			dmabuf->ops->unpin(attach);
> -			dma_resv_unlock(attach->dmabuf->resv);
> -		}
>   	}
> -
> -	dma_resv_lock(dmabuf->resv, NULL);
>   	list_del(&attach->node);
> +
>   	dma_resv_unlock(dmabuf->resv);
> +
>   	if (dmabuf->ops->detach)
>   		dmabuf->ops->detach(dmabuf, attach);
>