On Thu, Mar 1, 2012 at 9:35 AM, Daniel Vetter <daniel.vetter at ffwll.ch> wrote:
> The mutex protects the attachment list and hence needs to be held
> around the callbakc to the exporters (optional) attach/detach
> functions.
>
> Holding the mutex around the map/unmap calls doesn't protect any
> dma_buf state. Exporters need to properly protect any of their own
> state anyway (to protect against calls from their own interfaces).
> So this only makes the locking messier (and lockdep easier to anger).
>
> Therefore let's just drop this.
>
> Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>
Reviewed-by: Rob Clark <rob.clark at linaro.org>
> ---
> ?drivers/base/dma-buf.c ?| ? ?4 ----
> ?include/linux/dma-buf.h | ? ?2 +-
> ?2 files changed, 1 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/base/dma-buf.c b/drivers/base/dma-buf.c
> index e38ad24..1b11192 100644
> --- a/drivers/base/dma-buf.c
> +++ b/drivers/base/dma-buf.c
> @@ -258,10 +258,8 @@ struct sg_table *dma_buf_map_attachment(struct
> dma_buf_attachment *attach,
> ? ? ? ?if (WARN_ON(!attach || !attach->dmabuf || !attach->dmabuf->ops))
> ? ? ? ? ? ? ? ?return ERR_PTR(-EINVAL);
>
> - ? ? ? mutex_lock(&attach->dmabuf->lock);
> ? ? ? ?if (attach->dmabuf->ops->map_dma_buf)
> ? ? ? ? ? ? ? ?sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
> - ? ? ? mutex_unlock(&attach->dmabuf->lock);
>
> ? ? ? ?return sg_table;
> ?}
> @@ -282,10 +280,8 @@ void dma_buf_unmap_attachment(struct dma_buf_attachment
> *attach,
> ? ? ? ? ? ? ? ? ? ? ? ? ? ?|| !attach->dmabuf->ops))
> ? ? ? ? ? ? ? ?return;
>
> - ? ? ? mutex_lock(&attach->dmabuf->lock);
> ? ? ? ?if (attach->dmabuf->ops->unmap_dma_buf)
> ? ? ? ? ? ? ? ?attach->dmabuf->ops->unmap_dma_buf(attach, sg_table);
> - ? ? ? mutex_unlock(&attach->dmabuf->lock);
>
> ?}
> ?EXPORT_SYMBOL_GPL(dma_buf_unmap_attachment);
> diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
> index f8ac076..f7ad2ca 100644
> --- a/include/linux/dma-buf.h
> +++ b/include/linux/dma-buf.h
> @@ -86,7 +86,7 @@ struct dma_buf {
> ? ? ? ?struct file *file;
> ? ? ? ?struct list_head attachments;
> ? ? ? ?const struct dma_buf_ops *ops;
> - ? ? ? /* mutex to serialize list manipulation and other ops */
> + ? ? ? /* mutex to serialize list manipulation and attach/detach */
> ? ? ? ?struct mutex lock;
> ? ? ? ?void *priv;
> ?};
> --
> 1.7.7.5
>
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