linux-kernel - Re: [PATCH v6 1/2] drm: Unplug drm device when unregistering it

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Date:   Mon, 10 Apr 2017 15:38:44 -0400
From:   Sean Paul <seanpaul@...omium.org>
To:     Jeffy Chen <jeffy.chen@...k-chips.com>
Cc:     linux-kernel@...r.kernel.org, briannorris@...omium.org,
        dianders@...omium.org, tfiga@...omium.org, seanpaul@...omium.org,
        zyw@...k-chips.com, marcheu@...omium.org, mark.yao@...k-chips.com,
        hshi@...omium.org, Daniel Vetter <daniel.vetter@...el.com>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        dri-devel@...ts.freedesktop.org,
        Chris Wilson <chris@...is-wilson.co.uk>,
        David Airlie <airlied@...ux.ie>, Tom Gundersen <teg@...m.no>,
        Patrik Jakobsson <patrik.r.jakobsson@...il.com>,
        Dave Airlie <airlied@...hat.com>
Subject: Re: [PATCH v6 1/2] drm: Unplug drm device when unregistering it

On Mon, Apr 10, 2017 at 06:00:44PM +0800, Jeffy Chen wrote:
> After unbinding drm, the user space may still owns the drm dev fd,
> and may still be able to call drm ioctl.
> 
> We're using an unplugged state to prevent something like that, so
> let's reuse it here.
> 
> Signed-off-by: Jeffy Chen <jeffy.chen@...k-chips.com>
> ---
> 
> Changes in v6:
> Address Daniel Vetter <daniel@...ll.ch>'s comments.
> 
> Changes in v5:
> Fix wrong git account.
> 
> Changes in v2:
> Fix some commit messages.
> 
>  drivers/gpu/drm/drm_drv.c     | 6 +++---
>  drivers/gpu/drm/udl/udl_drv.c | 2 +-
>  include/drm/drmP.h            | 6 ++++++
>  3 files changed, 10 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
> index b5c6bb4..f38de26 100644
> --- a/drivers/gpu/drm/drm_drv.c
> +++ b/drivers/gpu/drm/drm_drv.c
> @@ -357,9 +357,6 @@ EXPORT_SYMBOL(drm_put_dev);
>  
>  void drm_unplug_dev(struct drm_device *dev)
>  {
> -	/* for a USB device */
> -	drm_dev_unregister(dev);
> -
>  	mutex_lock(&drm_global_mutex);
>  
>  	drm_device_set_unplugged(dev);
> @@ -787,6 +784,8 @@ int drm_dev_register(struct drm_device *dev, unsigned long flags)
>  	if (drm_core_check_feature(dev, DRIVER_MODESET))
>  		drm_modeset_register_all(dev);
>  
> +	drm_device_set_plugged(dev);
> +
>  	ret = 0;
>  
>  	DRM_INFO("Initialized %s %d.%d.%d %s for %s on minor %d\n",
> @@ -826,6 +825,7 @@ void drm_dev_unregister(struct drm_device *dev)
>  	drm_lastclose(dev);
>  
>  	dev->registered = false;
> +	drm_unplug_dev(dev);
>  
>  	if (drm_core_check_feature(dev, DRIVER_MODESET))
>  		drm_modeset_unregister_all(dev);
> diff --git a/drivers/gpu/drm/udl/udl_drv.c b/drivers/gpu/drm/udl/udl_drv.c
> index cd8b017..5dbd916 100644
> --- a/drivers/gpu/drm/udl/udl_drv.c
> +++ b/drivers/gpu/drm/udl/udl_drv.c
> @@ -108,7 +108,7 @@ static void udl_usb_disconnect(struct usb_interface *interface)
>  	drm_kms_helper_poll_disable(dev);
>  	udl_fbdev_unplug(dev);
>  	udl_drop_usb(dev);
> -	drm_unplug_dev(dev);
> +	drm_dev_unregister(dev);
>  }
>  
>  /*
> diff --git a/include/drm/drmP.h b/include/drm/drmP.h
> index 3bfafcd..c930a77 100644
> --- a/include/drm/drmP.h
> +++ b/include/drm/drmP.h
> @@ -488,6 +488,12 @@ static __inline__ int drm_core_check_feature(struct drm_device *dev,
>  	return ((dev->driver->driver_features & feature) ? 1 : 0);
>  }
>  
> +static inline void drm_device_set_plugged(struct drm_device *dev)
> +{
> +	smp_wmb();
> +	atomic_set(&dev->unplugged, 0);
> +}
> +
>  static inline void drm_device_set_unplugged(struct drm_device *dev)

Instead of introducing a new function, just rename this to
drm_device_set_plug_state(struct drm_device *dev, bool plugged)

and call it from both plug and unplug

With that nit, this is

Reviewed-by: Sean Paul <seanpaul@...omium.org>

>  {
>  	smp_wmb();
> -- 
> 2.1.4
> 

-- 
Sean Paul, Software Engineer, Google / Chromium OS