On Mon, Jun 25, 2018 at 10:22:31AM +0200, Daniel Vetter wrote:
On Fri, Jun 22, 2018 at 04:11:01PM +0200, Christian König wrote:
First step towards unpinned DMA buf operation.
I've checked the DRM drivers to potential locking of the reservation object, but essentially we need to audit all implementations of the dma_buf _ops for this to work.
v2: reordered
Signed-off-by: Christian König christian.koenig@amd.com
Reviewed-by: Daniel Vetter daniel.vetter@ffwll.ch
Ok I did review drivers a bit, but apparently not well enough by far. i915 CI is unhappy:
https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_9400/fi-whl-u/igt@gem_mma...
So yeah inserting that lock in there isn't the most trivial thing :-/
I kinda assume that other drivers will have similar issues, e.g. omapdrm's use of dev->struct_mutex also very much looks like it'll result in a new locking inversion. -Daniel
drivers/dma-buf/dma-buf.c | 9 ++++++--- include/linux/dma-buf.h | 4 ++++ 2 files changed, 10 insertions(+), 3 deletions(-)
diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c index dc94e76e2e2a..49f23b791eb8 100644 --- a/drivers/dma-buf/dma-buf.c +++ b/drivers/dma-buf/dma-buf.c @@ -665,7 +665,9 @@ struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach, if (WARN_ON(!attach || !attach->dmabuf)) return ERR_PTR(-EINVAL);
- sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
- reservation_object_lock(attach->dmabuf->resv, NULL);
- sg_table = dma_buf_map_attachment_locked(attach, direction);
- reservation_object_unlock(attach->dmabuf->resv); if (!sg_table) sg_table = ERR_PTR(-ENOMEM);
@@ -715,8 +717,9 @@ void dma_buf_unmap_attachment(struct dma_buf_attachment *attach, if (WARN_ON(!attach || !attach->dmabuf || !sg_table)) return;
- attach->dmabuf->ops->unmap_dma_buf(attach, sg_table,
direction);
- reservation_object_lock(attach->dmabuf->resv, NULL);
- dma_buf_unmap_attachment_locked(attach, sg_table, direction);
- reservation_object_unlock(attach->dmabuf->resv);
} EXPORT_SYMBOL_GPL(dma_buf_unmap_attachment); diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h index a25e754ae2f7..024658d1f22e 100644 --- a/include/linux/dma-buf.h +++ b/include/linux/dma-buf.h @@ -118,6 +118,8 @@ struct dma_buf_ops { * any other kind of sharing that the exporter might wish to make * available to buffer-users. *
* This is called with the dmabuf->resv object locked.*
- Returns:
- A &sg_table scatter list of or the backing storage of the DMA buffer,
@@ -138,6 +140,8 @@ struct dma_buf_ops { * It should also unpin the backing storage if this is the last mapping * of the DMA buffer, it the exporter supports backing storage * migration.
** This is called with the dmabuf->resv object locked.-- 2.14.1
-- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch