dma-buf: don't hold the mutex around map/unmap calls (6b607e3a) · Commits · 戴 / test

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. v2: Rebased on top of latest dma-buf-next git. Signed-off-by:

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

Rob Clark <rob.clark@linaro.org> Signed-off-by:

Sumit Semwal <sumit.semwal@linaro.org>

drivers/base/dma-buf.c

+0 −5

Original line number	Diff line number	Diff line
		@@ -258,9 +258,7 @@ struct sg_table dma_buf_map_attachment(struct dma_buf_attachment attach,
		if (WARN_ON(!attach \|\| !attach->dmabuf))
		return ERR_PTR(-EINVAL);

		mutex_lock(&attach->dmabuf->lock);
		sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
		mutex_unlock(&attach->dmabuf->lock);

		return sg_table;
		}
		@@ -282,10 +280,7 @@ void dma_buf_unmap_attachment(struct dma_buf_attachment *attach,
		if (WARN_ON(!attach \|\| !attach->dmabuf \|\| !sg_table))
		return;

		mutex_lock(&attach->dmabuf->lock);
		attach->dmabuf->ops->unmap_dma_buf(attach, sg_table,
		direction);
		mutex_unlock(&attach->dmabuf->lock);

		}
		EXPORT_SYMBOL_GPL(dma_buf_unmap_attachment);

include/linux/dma-buf.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -88,7 +88,7 @@ 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;
		};

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