linux-kernel - Re: [PATCH v7 1/2] drm: Unplug drm device when unregistering it

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Message-ID: <20170412063318.mzijyktw6kp7e4uo@phenom.ffwll.local>
Date:   Wed, 12 Apr 2017 08:33:18 +0200
From:   Daniel Vetter <daniel@...ll.ch>
To:     Jeffy Chen <jeffy.chen@...k-chips.com>
Cc:     linux-kernel@...r.kernel.org, Dave Airlie <airlied@...hat.com>,
        briannorris@...omium.org, dianders@...omium.org,
        tfiga@...omium.org, dri-devel@...ts.freedesktop.org,
        Daniel Vetter <daniel.vetter@...el.com>, zyw@...k-chips.com,
        marcheu@...omium.org, hshi@...omium.org
Subject: Re: [PATCH v7 1/2] drm: Unplug drm device when unregistering it

On Tue, Apr 11, 2017 at 11:31:41AM +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>
> Reviewed-by: Sean Paul <seanpaul@...omium.org>
> 
> ---
> 
> Changes in v7:
> Address Sean Paul <seanpaul@...omium.org>'s comments.
> 
> Changes in v6:
> Address Daniel Vetter <daniel@...ll.ch>'s comments.

Please don't just list the names, but what you've changed. As-is this
isn't very informative ... Also, in drm we prefer the patch changelog
above the --- line, for more credit to the review process.

A few questions below.
-Daniel

> 
> Changes in v5:
> Fix wrong git account.
> 
> Changes in v2:
> Fix some commit messages.
> 
>  drivers/gpu/drm/drm_drv.c     | 8 ++++----
>  drivers/gpu/drm/udl/udl_drv.c | 2 +-
>  include/drm/drmP.h            | 5 +++--
>  3 files changed, 8 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
> index b5c6bb4..ad13e20 100644
> --- a/drivers/gpu/drm/drm_drv.c
> +++ b/drivers/gpu/drm/drm_drv.c
> @@ -357,12 +357,9 @@ EXPORT_SYMBOL(drm_put_dev);
>  
>  void drm_unplug_dev(struct drm_device *dev)

I think this function can now be unexported and made static?

>  {
> -	/* for a USB device */
> -	drm_dev_unregister(dev);
> -
>  	mutex_lock(&drm_global_mutex);
>  
> -	drm_device_set_unplugged(dev);
> +	drm_device_set_plug_state(dev, false);
>  
>  	if (dev->open_count == 0) {
>  		drm_put_dev(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_plug_state(dev, true);
> +
>  	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..a9a5a64 100644
> --- a/include/drm/drmP.h
> +++ b/include/drm/drmP.h
> @@ -488,10 +488,11 @@ 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_unplugged(struct drm_device *dev)
> +static inline void drm_device_set_plug_state(struct drm_device *dev,
> +					     bool plugged)

Why this change here? I thought the plan was to just unplug _all_ devices
at unregister time? Also, I think we want to make this into a static
function in drm_drv.c

>  {
>  	smp_wmb();
> -	atomic_set(&dev->unplugged, 1);
> +	atomic_set(&dev->unplugged, !plugged);
>  }
>  
>  static inline int drm_device_is_unplugged(struct drm_device *dev)
> -- 
> 2.1.4
> 
> 
> _______________________________________________
> dri-devel mailing list
> dri-devel@...ts.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

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

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