Re: [PATCH v2 3/3] drm/vc4: Convert more lock requirement comments to lockdep assertions.

[Daniel Vetter]

On Tue, Jul 25, 2017 at 11:27:18AM -0700, Eric Anholt wrote:
> Since I do my development with lockdep on, this will help make sure I
> don't introduce bugs here.

Yeah it's somewhat annoying that lockdep_assert_held doesn't reduce to a
"no false positives, maybe some false negatives, but real fast" runtime
check without lockdep and just mutex debugging enabled. We even have it as
mutex_is_locked already. But not doing to fight that bikeshed :-/

> Signed-off-by: Eric Anholt <eric@xxxxxxxxxx>

Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>

> ---
>  drivers/gpu/drm/vc4/vc4_bo.c | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/vc4/vc4_bo.c b/drivers/gpu/drm/vc4/vc4_bo.c
> index f4387e1e178d..b24dd8685590 100644
> --- a/drivers/gpu/drm/vc4/vc4_bo.c
> +++ b/drivers/gpu/drm/vc4/vc4_bo.c
> @@ -163,10 +163,12 @@ static uint32_t bo_page_index(size_t size)
>  	return (size / PAGE_SIZE) - 1;
>  }
>  
> -/* Must be called with bo_lock held. */
>  static void vc4_bo_destroy(struct vc4_bo *bo)
>  {
>  	struct drm_gem_object *obj = &bo->base.base;
> +	struct vc4_dev *vc4 = to_vc4_dev(obj->dev);
> +
> +	lockdep_assert_held(&vc4->bo_lock);
>  
>  	vc4_bo_set_label(obj, -1);
>  
> @@ -181,9 +183,11 @@ static void vc4_bo_destroy(struct vc4_bo *bo)
>  	drm_gem_cma_free_object(obj);
>  }
>  
> -/* Must be called with bo_lock held. */
>  static void vc4_bo_remove_from_cache(struct vc4_bo *bo)
>  {
> +	struct vc4_dev *vc4 = to_vc4_dev(bo->base.base.dev);
> +
> +	lockdep_assert_held(&vc4->bo_lock);
>  	list_del(&bo->unref_head);
>  	list_del(&bo->size_head);
>  }
> @@ -367,12 +371,13 @@ int vc4_dumb_create(struct drm_file *file_priv,
>  	return ret;
>  }
>  
> -/* Must be called with bo_lock held. */
>  static void vc4_bo_cache_free_old(struct drm_device *dev)
>  {
>  	struct vc4_dev *vc4 = to_vc4_dev(dev);
>  	unsigned long expire_time = jiffies - msecs_to_jiffies(1000);
>  
> +	lockdep_assert_held(&vc4->bo_lock);
> +
>  	while (!list_empty(&vc4->bo_cache.time_list)) {
>  		struct vc4_bo *bo = list_last_entry(&vc4->bo_cache.time_list,
>  						    struct vc4_bo, unref_head);
> -- 
> 2.11.0
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch