Re: [PATCH v2] drm/atomic: Handle vblank events in atomic ioctl correctly.

[Daniel Vetter <daniel@ffwll.ch>]

On Tue, Jun 02, 2015 at 09:00:46AM +0200, Maarten Lankhorst wrote:
> All users of async updates seem to clear clear crtc_state->event
> correctly, so move destroying vblank event to crtc_destroy_state.
> 
> This is better than manually free'ing it in the atomic ioctl, since
> this code seems to do it wrong.
> 
> While we're at it handle -EDEADLK from atomic_commit correctly,
> because the check might fail otherwise if it takes additional state.

Please don't smash unrelated fixes together into the same patch.

> Changes since v1:
> - Fix freeing a NULL framebuffer, thanks for catching Daniel Stone.
> 
> Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Reviewed-by: Daniel Stone <daniels@collabora.com>
> ---
>  drivers/gpu/drm/drm_atomic.c        | 45 +++++++++----------------------------
>  drivers/gpu/drm/drm_atomic_helper.c | 15 +++++++++++++
>  2 files changed, 26 insertions(+), 34 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> index c7e59b074e62..8add0dd8dc5d 100644
> --- a/drivers/gpu/drm/drm_atomic.c
> +++ b/drivers/gpu/drm/drm_atomic.c
> @@ -1328,17 +1328,6 @@ out:
>  	return e;
>  }
>  
> -static void destroy_vblank_event(struct drm_device *dev,
> -		struct drm_file *file_priv, struct drm_pending_vblank_event *e)
> -{
> -	unsigned long flags;
> -
> -	spin_lock_irqsave(&dev->event_lock, flags);
> -	file_priv->event_space += sizeof e->event;
> -	spin_unlock_irqrestore(&dev->event_lock, flags);
> -	kfree(e);
> -}
> -
>  static int atomic_set_prop(struct drm_atomic_state *state,
>  		struct drm_mode_object *obj, struct drm_property *prop,
>  		uint64_t prop_value)
> @@ -1534,13 +1523,18 @@ retry:
>  	if (arg->flags & DRM_MODE_ATOMIC_TEST_ONLY) {
>  		ret = drm_atomic_check_only(state);
>  		/* _check_only() does not free state, unlike _commit() */
> -		drm_atomic_state_free(state);
> +		if (!ret)
> +			drm_atomic_state_free(state);
>  	} else if (arg->flags & DRM_MODE_ATOMIC_NONBLOCK) {
>  		ret = drm_atomic_async_commit(state);
>  	} else {
>  		ret = drm_atomic_commit(state);
>  	}
>  
> +fail:
> +	if (ret == -EDEADLK)
> +		goto backoff;
> +
>  	/* if succeeded, fixup legacy plane crtc/fb ptrs before dropping
>  	 * locks (ie. while it is still safe to deref plane->state).  We
>  	 * need to do this here because the driver entry points cannot
> @@ -1553,32 +1547,15 @@ retry:
>  				drm_framebuffer_reference(new_fb);
>  			plane->fb = new_fb;
>  			plane->crtc = plane->state->crtc;
> -		} else {
> -			plane->old_fb = NULL;
> -		}
> -		if (plane->old_fb) {
> -			drm_framebuffer_unreference(plane->old_fb);
> -			plane->old_fb = NULL;
> -		}
> -	}
> -
> -	drm_modeset_drop_locks(&ctx);
> -	drm_modeset_acquire_fini(&ctx);
> -
> -	return ret;
> -
> -fail:
> -	if (ret == -EDEADLK)
> -		goto backoff;

We have a pre-existing bug here already of leaking plane->old_fb before
dropping locks. I think the EDEADLK case needs to be after the cleanup
loop to clear old_fb.
-Daniel

>  
> -	if (arg->flags & DRM_MODE_PAGE_FLIP_EVENT) {
> -		for_each_crtc_in_state(state, crtc, crtc_state, i) {
> -			destroy_vblank_event(dev, file_priv, crtc_state->event);
> -			crtc_state->event = NULL;
> +			if (plane->old_fb)
> +				drm_framebuffer_unreference(plane->old_fb);
>  		}
> +		plane->old_fb = NULL;
>  	}
>  
> -	drm_atomic_state_free(state);
> +	if (ret)
> +		drm_atomic_state_free(state);
>  
>  	drm_modeset_drop_locks(&ctx);
>  	drm_modeset_acquire_fini(&ctx);
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index 536ae4da4665..0bb70c4da77a 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -2101,6 +2101,18 @@ drm_atomic_helper_crtc_duplicate_state(struct drm_crtc *crtc)
>  }
>  EXPORT_SYMBOL(drm_atomic_helper_crtc_duplicate_state);
>  
> +static void destroy_vblank_event(struct drm_device *dev,
> +		struct drm_pending_vblank_event *e)
> +{
> +	struct drm_file *file_priv = e->base.file_priv;
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&dev->event_lock, flags);
> +	file_priv->event_space += sizeof e->event;
> +	spin_unlock_irqrestore(&dev->event_lock, flags);
> +	kfree(e);
> +}
> +
>  /**
>   * __drm_atomic_helper_crtc_destroy_state - release CRTC state
>   * @crtc: CRTC object
> @@ -2115,6 +2127,9 @@ void __drm_atomic_helper_crtc_destroy_state(struct drm_crtc *crtc,
>  {
>  	if (state->mode_blob)
>  		drm_property_unreference_blob(state->mode_blob);
> +
> +	if (state->event)
> +		destroy_vblank_event(crtc->dev, state->event);
>  }
>  EXPORT_SYMBOL(__drm_atomic_helper_crtc_destroy_state);
>  
> -- 
> 2.1.0
> 
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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