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

[jeffy <jeffy.chen@rock-chips.com>]

Hi Daniel,

On 04/12/2017 02:33 PM, Daniel Vetter wrote:
> 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@rock-chips.com>
>> Reviewed-by: Sean Paul <seanpaul@chromium.org>
>>
>> ---
>>
>> Changes in v7:
>> Address Sean Paul <seanpaul@chromium.org>'s comments.
>>
>> Changes in v6:
>> Address Daniel Vetter <daniel@ffwll.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
calling drm_unplug_dev when unregistering drm device may cause 
hang(drm_unplug_dev will try to put drm dev when open_count is 0).

so i think we only need to update the unplug state at that time?

maybe put drm_device_set_plug_state into drm_drv.c(because no one else 
would use it)?
>
>>   {
>>   	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
>>
>>
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>