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

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

Hi Daniel,

missed some questions...

On 04/12/2017 04:17 PM, jeffy wrote:
> 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.
>>
oops, sorry, the --- line and changelogs are ordered by patman tool, 
i'll try to check did i config that wrong.

>> 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?
there's a patch v8, which removed this function :)
>>
>>>   {
>>> -    /* 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
>>>
>>>
>>> _______________________________________________
>>> dri-devel mailing list
>>> dri-devel@lists.freedesktop.org
>>> https://lists.freedesktop.org/mailman/listinfo/dri-devel
>>
>