Re: [PATCH 1/4] drm: Add a non-locking version of drm_kms_helper_poll_enable().

[Daniel Vetter <daniel@ffwll.ch>]

On Tue, Sep 01, 2015 at 10:21:32PM +0200, Egbert Eich wrote:
> drm_kms_helper_poll_enable() was converted to lock the mode_config
> mutex in commit 8c4ccc4ab6f64e859d4ff8d7c02c2ed2e956e07f
> ("drm/probe-helper: Grab mode_config.mutex in poll_init/enable").
> 
> This disregarded the cases where this function is called from a context
> where this mutex is already locked.
> 
> Add a non-locking version as well.
> 
> Signed-off-by: Egbert Eich <eich@suse.de>
> ---
>  drivers/gpu/drm/drm_probe_helper.c | 19 ++++++++++++++++---
>  include/drm/drm_crtc_helper.h      |  1 +
>  2 files changed, 17 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_probe_helper.c b/drivers/gpu/drm/drm_probe_helper.c
> index d734780..a93ad1b 100644
> --- a/drivers/gpu/drm/drm_probe_helper.c
> +++ b/drivers/gpu/drm/drm_probe_helper.c
> @@ -93,8 +93,19 @@ static int drm_helper_probe_add_cmdline_mode(struct drm_connector *connector)
>  	return 1;
>  }
>  
> +/**
> + * drm_kms_helper_poll_enable_no_lock - re-enable output polling.
> + * @dev: drm_device
> + *
> + * This function re-enables the output polling work without
> + * locking the mode_config mutex.
> + *
> + * This is like drm_kms_helper_poll_enable() however it is to be
> + * called from a context where the mode_config mutex is locked
> + * already.
> + */
>  #define DRM_OUTPUT_POLL_PERIOD (10*HZ)
> -static void __drm_kms_helper_poll_enable(struct drm_device *dev)
> +void drm_kms_helper_poll_enable_no_lock(struct drm_device *dev)

Please use _locked to stay consistent with other such functions. With that
address this lgtm.
-Daniel

>  {
>  	bool poll = false;
>  	struct drm_connector *connector;
> @@ -113,6 +124,8 @@ static void __drm_kms_helper_poll_enable(struct drm_device *dev)
>  	if (poll)
>  		schedule_delayed_work(&dev->mode_config.output_poll_work, DRM_OUTPUT_POLL_PERIOD);
>  }
> +EXPORT_SYMBOL(drm_kms_helper_poll_enable_no_lock);
> +
>  
>  static int drm_helper_probe_single_connector_modes_merge_bits(struct drm_connector *connector,
>  							      uint32_t maxX, uint32_t maxY, bool merge_type_bits)
> @@ -174,7 +187,7 @@ static int drm_helper_probe_single_connector_modes_merge_bits(struct drm_connect
>  
>  	/* Re-enable polling in case the global poll config changed. */
>  	if (drm_kms_helper_poll != dev->mode_config.poll_running)
> -		__drm_kms_helper_poll_enable(dev);
> +		drm_kms_helper_poll_enable_no_lock(dev);
>  
>  	dev->mode_config.poll_running = drm_kms_helper_poll;
>  
> @@ -428,7 +441,7 @@ EXPORT_SYMBOL(drm_kms_helper_poll_disable);
>  void drm_kms_helper_poll_enable(struct drm_device *dev)
>  {
>  	mutex_lock(&dev->mode_config.mutex);
> -	__drm_kms_helper_poll_enable(dev);
> +	drm_kms_helper_poll_enable_no_lock(dev);
>  	mutex_unlock(&dev->mode_config.mutex);
>  }
>  EXPORT_SYMBOL(drm_kms_helper_poll_enable);
> diff --git a/include/drm/drm_crtc_helper.h b/include/drm/drm_crtc_helper.h
> index 2a747a9..f96703d 100644
> --- a/include/drm/drm_crtc_helper.h
> +++ b/include/drm/drm_crtc_helper.h
> @@ -240,5 +240,6 @@ extern void drm_kms_helper_hotplug_event(struct drm_device *dev);
>  
>  extern void drm_kms_helper_poll_disable(struct drm_device *dev);
>  extern void drm_kms_helper_poll_enable(struct drm_device *dev);
> +extern void drm_kms_helper_poll_enable_no_lock(struct drm_device *dev);
>  
>  #endif
> -- 
> 1.8.4.5
> 

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