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@xxxxxxx> > > Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx> 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_mmap_gtt@xxxxxxxxxxxxxxxxxxxxxxxxxx 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. > > */ > > void (*unmap_dma_buf)(struct dma_buf_attachment *, > > struct sg_table *, > > -- > > 2.14.1 > > > > -- > Daniel Vetter > Software Engineer, Intel Corporation > http://blog.ffwll.ch -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch
