Re: [PATCH v2] drm/gem: add mutex lock when using drm_gem_mmap_obj

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi,


On Thursday 27 June 2013 08:39:58 Seung-Woo Kim wrote:
> From: YoungJun Cho <yj44.cho@samsung.com>
> 
> The drm_gem_mmap_obj() has to be protected with dev->struct_mutex,
> but some caller functions do not. So it adds mutex lock to missing
> callers and adds assertion to check whether drm_gem_mmap_obj() is
> called with mutex lock or not.
> 
> Signed-off-by: YoungJun Cho <yj44.cho@samsung.com>
> Signed-off-by: Seung-Woo Kim <sw0312.kim@samsung.com>
> Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
> CC: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
> CC: Rob Clark <robdclark@gmail.com>

Thanks for the patch.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

> ---
> This patch is based on drm-next branch.
> 
> Changes since v1:
> - Use lockdep_assert_held() instead of mutex_is_locked() as Maarten
> commented
> - Fix commit message about assertion
> 
>  drivers/gpu/drm/drm_gem.c                 |    4 ++++
>  drivers/gpu/drm/drm_gem_cma_helper.c      |    3 +++
>  drivers/gpu/drm/omapdrm/omap_gem_dmabuf.c |    3 +++
>  3 files changed, 10 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
> index 4321713..34c0be7 100644
> --- a/drivers/gpu/drm/drm_gem.c
> +++ b/drivers/gpu/drm/drm_gem.c
> @@ -661,6 +661,8 @@ EXPORT_SYMBOL(drm_gem_vm_close);
>   * the GEM object is not looked up based on its fake offset. To implement
> the * DRM mmap operation, drivers should use the drm_gem_mmap() function. *
> + * NOTE: This function has to be protected with dev->struct_mutex
> + *
>   * Return 0 or success or -EINVAL if the object size is smaller than the
> VMA * size, or if no gem_vm_ops are provided.
>   */
> @@ -669,6 +671,8 @@ int drm_gem_mmap_obj(struct drm_gem_object *obj,
> unsigned long obj_size, {
>  	struct drm_device *dev = obj->dev;
> 
> +	lockdep_assert_held(&dev->struct_mutex);
> +
>  	/* Check for valid size. */
>  	if (obj_size < vma->vm_end - vma->vm_start)
>  		return -EINVAL;
> diff --git a/drivers/gpu/drm/drm_gem_cma_helper.c
> b/drivers/gpu/drm/drm_gem_cma_helper.c index 9efabce..ce06397 100644
> --- a/drivers/gpu/drm/drm_gem_cma_helper.c
> +++ b/drivers/gpu/drm/drm_gem_cma_helper.c
> @@ -487,9 +487,12 @@ static int drm_gem_cma_dmabuf_mmap(struct dma_buf
> *dmabuf, {
>  	struct drm_gem_cma_object *cma_obj = dmabuf->priv;
>  	struct drm_gem_object *gem_obj = &cma_obj->base;
> +	struct drm_device *dev = gem_obj->dev;
>  	int ret;
> 
> +	mutex_lock(&dev->struct_mutex);
>  	ret = drm_gem_mmap_obj(gem_obj, gem_obj->size, vma);
> +	mutex_unlock(&dev->struct_mutex);
>  	if (ret < 0)
>  		return ret;
> 
> diff --git a/drivers/gpu/drm/omapdrm/omap_gem_dmabuf.c
> b/drivers/gpu/drm/omapdrm/omap_gem_dmabuf.c index 3256693..4fcca8d 100644
> --- a/drivers/gpu/drm/omapdrm/omap_gem_dmabuf.c
> +++ b/drivers/gpu/drm/omapdrm/omap_gem_dmabuf.c
> @@ -140,12 +140,15 @@ static int omap_gem_dmabuf_mmap(struct dma_buf
> *buffer, struct vm_area_struct *vma)
>  {
>  	struct drm_gem_object *obj = buffer->priv;
> +	struct drm_device *dev = obj->dev;
>  	int ret = 0;
> 
>  	if (WARN_ON(!obj->filp))
>  		return -EINVAL;
> 
> +	mutex_lock(&dev->struct_mutex);
>  	ret = drm_gem_mmap_obj(obj, omap_gem_mmap_size(obj), vma);
> +	mutex_unlock(&dev->struct_mutex);
>  	if (ret < 0)
>  		return ret;
-- 
Regards,

Laurent Pinchart