Re: [PATCH] drm: Fixup locking WARNINGs in drm_mode_config_reset

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

Hi Daniel,

Thank you for the patch.

On Wednesday 29 July 2015 08:32:43 Daniel Vetter wrote:
> With
> 
> commit 7a3f3d6667f5f9ffd1517f6b21d64bbf5312042c
> Author: Daniel Vetter <daniel.vetter@ffwll.ch>
> Date:   Thu Jul 9 23:44:28 2015 +0200
> 
>     drm: Check locking in drm_for_each_connector
> 
> we started checking the locking in drm_for_each_connector but somehow
> I totally missed drm_mode_config_reset. There's no problem there since
> this function should only be called in single-threaded contexts
> (driver load or resume), so just wrap the loop with the right lock.
> 
> v2: Drink coffee and all that ...
> 
> Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> Reported-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>

This gets rid of the warning at driver load time with the rcar-du-drm driver.

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

> ---
>  drivers/gpu/drm/drm_crtc.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
> index c91c18b2b1d4..10c1a0f6680c 100644
> --- a/drivers/gpu/drm/drm_crtc.c
> +++ b/drivers/gpu/drm/drm_crtc.c
> @@ -5273,9 +5273,11 @@ void drm_mode_config_reset(struct drm_device *dev)
>  		if (encoder->funcs->reset)
>  			encoder->funcs->reset(encoder);
> 
> +	mutex_lock(&dev->mode_config.mutex);
>  	drm_for_each_connector(connector, dev)
>  		if (connector->funcs->reset)
>  			connector->funcs->reset(connector);
> +	mutex_unlock(&dev->mode_config.mutex);

Wouldn't it make sense to protect the whole function with the mode_config 
mutex, given that it's documented as "protecting the KMS related lists and 
structures" ?

>  }
>  EXPORT_SYMBOL(drm_mode_config_reset);

-- 
Regards,

Laurent Pinchart

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