Hi Chris,
On Friday 21 Apr 2017 00:08:21 Chris Wilson wrote:
> On Fri, Apr 21, 2017 at 12:33:59AM +0300, Laurent Pinchart wrote:
> > To ensure that neither the GEM object nor the DRM device goes away while
> > a GEM object exported through dma-buf is still accessible, take a
> > reference to both the GEM object and the DRM device at export time. The
> > dma-buf release handler already releases the GEM object (which resulted
> > in a refcount underflow) and now also releases the DRM device.
> >
> > Fixes: 6ad11bc3a0b8 ("staging: drm/omap: dmabuf/prime support")
> > Signed-off-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> > ---
> >
> > drivers/gpu/drm/omapdrm/omap_gem_dmabuf.c | 17 +++++++++++++----
> > 1 file changed, 13 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/omapdrm/omap_gem_dmabuf.c
> > b/drivers/gpu/drm/omapdrm/omap_gem_dmabuf.c index
> > 79dfded9613c..88ad723b3044 100644
> > --- a/drivers/gpu/drm/omapdrm/omap_gem_dmabuf.c
> > +++ b/drivers/gpu/drm/omapdrm/omap_gem_dmabuf.c
> > @@ -75,10 +75,11 @@ static void omap_gem_unmap_dma_buf(struct
> > dma_buf_attachment *attachment,>
> > static void omap_gem_dmabuf_release(struct dma_buf *buffer)
> > {
> >
> > struct drm_gem_object *obj = buffer->priv;
> >
> > - /* release reference that was taken when dmabuf was exported
> > - * in omap_gem_prime_set()..
> > - */
> > + struct drm_device *dev = obj->dev;
> > +
> > + /* Release references taken by omap_gem_prime_export(). */
> >
> > drm_gem_object_unreference_unlocked(obj);
> >
> > + drm_dev_ref(dev);
> >
> > }
> >
> > @@ -184,13 +185,21 @@ struct dma_buf *omap_gem_prime_export(struct
> > drm_device *dev,>
> > struct drm_gem_object *obj, int flags)
> >
> > {
> >
> > DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
> >
> > + struct dma_buf *dma_buf;
> >
> > exp_info.ops = &omap_dmabuf_ops;
> > exp_info.size = obj->size;
> > exp_info.flags = flags;
> > exp_info.priv = obj;
> >
> > - return dma_buf_export(&exp_info);
> > + dma_buf = dma_buf_export(&exp_info);
> > + if (IS_ERR(dma_buf))
> > + return dma_buf;
> > +
> > + drm_dev_ref(dev);
> > + drm_gem_object_reference(obj);
> > +
> > + return dma_buf;
> >
> > }
>
> Please see drm_gem_dmabuf_export() and drm_gem_dmabuf_release()
Good point, I'll replace the custom implementation by those functions. I had
noticed drm_gem_dmabuf_release() but for some reason failed to see that
drm_gem_dmabuf_export() was exported.
> - unless the double drm_dev_ref() wasn't an accident...
Oops :-/ Thank you for catching that.
--
Regards,
Laurent Pinchart
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