[PATCH] drm: fix drm_mode_getconnector() locking imbalance regression

[Daniel Vetter]

On Fri, Apr 03, 2015 at 10:45:29AM +0300, Tommi Rantala wrote:
> Regression in commit 2caa80e72b57c6216aec6f6a11fcfb4fec46daa0
> Author: Daniel Vetter <daniel.vetter at ffwll.ch>
> Date:   Sun Feb 22 11:38:36 2015 +0100
> 
>     drm: Fix deadlock due to getconnector locking changes
> 
> If the drm_connector_find() call returns NULL, we should no longer
> call drm_modeset_unlock() to avoid locking imbalance.
> 
> Signed-off-by: Tommi Rantala <tt.rantala at gmail.com>
> Cc: Daniel Vetter <daniel.vetter at ffwll.ch>

Oops, thanks for catching this. If this missed 4.0 then we need to
backport it.

Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>

> ---
>  drivers/gpu/drm/drm_crtc.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
> index 679b10e..b6f076b 100644
> --- a/drivers/gpu/drm/drm_crtc.c
> +++ b/drivers/gpu/drm/drm_crtc.c
> @@ -2121,7 +2121,7 @@ int drm_mode_getconnector(struct drm_device *dev, void *data,
>  	connector = drm_connector_find(dev, out_resp->connector_id);
>  	if (!connector) {
>  		ret = -ENOENT;
> -		goto out;
> +		goto out_unlock;
>  	}
>  
>  	for (i = 0; i < DRM_CONNECTOR_MAX_ENCODER; i++)
> @@ -2201,6 +2201,8 @@ int drm_mode_getconnector(struct drm_device *dev, void *data,
>  
>  out:
>  	drm_modeset_unlock(&dev->mode_config.connection_mutex);
> +
> +out_unlock:
>  	mutex_unlock(&dev->mode_config.mutex);
>  
>  	return ret;
> -- 
> 2.1.0
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch