On Wed, Aug 07, 2013 at 12:09:32PM +0200, Daniel Vetter wrote:
> This fixes a WARN in i915_gem_free_object when the
> obj->pages_pin_count isn't 0.
>
> v2: Add locking to unmap, noticed by Chris Wilson. Note that even
> though we call unmap with our own dev->struct_mutex held that won't
> result in an immediate deadlock since we never go through the dma_buf
> interfaces for our own, reimported buffers. But it's still easy to
> blow up and anger lockdep, but that's already the case with our ->map
> implementation. Fixing this for real will involve per dma-buf ww mutex
> locking by the callers. And lots of fun. So go with the duct-tape
> approach for now.
>
> Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Reported-by: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxx>
> Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxx>
> Tested-by: Armin K. <krejzi@xxxxxxxxx> (v1)
> Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
> ---
> drivers/gpu/drm/i915/i915_gem_dmabuf.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem_dmabuf.c b/drivers/gpu/drm/i915/i915_gem_dmabuf.c
> index 63ee1a9..f7e1682 100644
> --- a/drivers/gpu/drm/i915/i915_gem_dmabuf.c
> +++ b/drivers/gpu/drm/i915/i915_gem_dmabuf.c
> @@ -85,9 +85,17 @@ static void i915_gem_unmap_dma_buf(struct dma_buf_attachment *attachment,
> struct sg_table *sg,
> enum dma_data_direction dir)
> {
> + struct drm_i915_gem_object *obj = attachment->dmabuf->priv;
> +
> + mutex_lock(&obj->base.dev->struct_mutex);
> +
> dma_unmap_sg(attachment->dev, sg->sgl, sg->nents, dir);
> sg_free_table(sg);
> kfree(sg);
> +
> + i915_gem_object_unpin_pages(obj);
I am curious - would it logic of first unpinning, and then doing the dma_unmap_sg
make more sense? As in, in the map path we do:
dma_map
pin
And in here you do the same:
dma_unmap
unpin
But I would have thought that on a unroll you would do it in reverse
order, so:
unpin
dma_unmap
> +
> + mutex_unlock(&obj->base.dev->struct_mutex);
> }
>
> static void *i915_gem_dmabuf_vmap(struct dma_buf *dma_buf)
> --
> 1.8.3.2
>
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