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Re: [PATCH v11] drm: Unplug drm device when unregistering it (v8)

Started byChris Wilson <chris@chris-wilson.co.uk>
First post2017-05-29 22:30 +0200
Last post2017-06-01 14:30 +0200
Articles 8 — 4 participants

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  Re: [PATCH v11] drm: Unplug drm device when unregistering it (v8) Chris Wilson <chris@chris-wilson.co.uk> - 2017-05-29 22:30 +0200
    Re: [PATCH v11] drm: Unplug drm device when unregistering it (v8) Marco Diego Aurélio Mesquita          <marcodiegomesquita@gmail.com> - 2017-05-29 23:20 +0200
    Re: [PATCH v11] drm: Unplug drm device when unregistering it (v8) Hans de Goede <hdegoede@redhat.com> - 2017-05-30 09:10 +0200
      Re: [PATCH v11] drm: Unplug drm device when unregistering it (v8) jeffy <jeffy.chen@rock-chips.com> - 2017-05-31 04:50 +0200
        Re: [PATCH v11] drm: Unplug drm device when unregistering it (v8) Hans de Goede <hdegoede@redhat.com> - 2017-06-01 14:20 +0200
          Re: [PATCH v11] drm: Unplug drm device when unregistering it (v8) Hans de Goede <hdegoede@redhat.com> - 2017-06-01 14:30 +0200
            Re: [PATCH v11] drm: Unplug drm device when unregistering it (v8) Chris Wilson <chris@chris-wilson.co.uk> - 2017-06-01 15:10 +0200
          Re: [PATCH v11] drm: Unplug drm device when unregistering it (v8) Chris Wilson <chris@chris-wilson.co.uk> - 2017-06-01 14:30 +0200

#1652707 — Re: [PATCH v11] drm: Unplug drm device when unregistering it (v8)

FromChris Wilson <chris@chris-wilson.co.uk>
Date2017-05-29 22:30 +0200
SubjectRe: [PATCH v11] drm: Unplug drm device when unregistering it (v8)
Message-ID<tMzsB-58C-9@gated-at.bofh.it>
On Fri, Apr 14, 2017 at 11:15:04AM -0400, Sean Paul wrote:
> On Thu, Apr 13, 2017 at 03:32:44PM +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.
> > 
> > Also drop drm_unplug_dev, because it would be unused after other changes.
> > 
> > Verified on rk3399 chromebook kevin(with cros 4.4 kernel), no more crashes
> > when unbinding drm with ui service still running.
> > 
> > v2: Fix some commit messages.
> > v3: Reuse unplug status.
> > v4: Add drm_device_set_plug_state helper.
> > v5: Fix hang when unregistering drm dev with open_count 0.
> > v6: Move drm_device_set_plug_state into drm_drv.
> > v7: Add missing drm_dev_unref in udl_drv.
> > v8: Fix compiler errors after enable udl.
> > 
> > Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
> > 
> > ---
> 
> Hi Jeffy,
> Given the trouble we've had with this patch already, coupled with the fact that
> unbinding while userspace is active is a contrived/pathological case, I don't
> think it's worth picking this patch upstream.
> 
> If it's really causing issues downstream, you can add my Reviewed-by for a CHROMIUM
> patch, but I'd rather not carry patches in the CrOS repo if we don't need to.

Would a

Fixes: a39be606f99d ("drm: Do a full device unregister when unplugging")
Reported-by: Marco Diego Aurélio Mesquita <marcodiegomesquita@gmail.com>
Cc: Hans de Goede <hdegoede@redhat.com>

convince us to look into this patch again?
-Chris

> > 
> >  drivers/gpu/drm/drm_drv.c     | 26 ++++++++++----------------
> >  drivers/gpu/drm/udl/udl_drv.c |  3 ++-
> >  include/drm/drmP.h            |  6 ------
> >  include/drm/drm_drv.h         |  1 -
> >  4 files changed, 12 insertions(+), 24 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
> > index b5c6bb4..e1da4d1 100644
> > --- a/drivers/gpu/drm/drm_drv.c
> > +++ b/drivers/gpu/drm/drm_drv.c
> > @@ -355,22 +355,6 @@ void drm_put_dev(struct drm_device *dev)
> >  }
> >  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);
> > -
> > -	if (dev->open_count == 0) {
> > -		drm_put_dev(dev);
> > -	}
> > -	mutex_unlock(&drm_global_mutex);
> > -}
> > -EXPORT_SYMBOL(drm_unplug_dev);
> > -
> >  /*
> >   * DRM internal mount
> >   * We want to be able to allocate our own "struct address_space" to control
> > @@ -733,6 +717,13 @@ static void remove_compat_control_link(struct drm_device *dev)
> >  	kfree(name);
> >  }
> >  
> > +static inline void drm_device_set_plug_state(struct drm_device *dev,
> > +					     bool plugged)
> > +{
> > +	smp_wmb();
> > +	atomic_set(&dev->unplugged, !plugged);
> > +}
> > +
> >  /**
> >   * drm_dev_register - Register DRM device
> >   * @dev: Device to register
> > @@ -787,6 +778,8 @@ 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 +819,7 @@ void drm_dev_unregister(struct drm_device *dev)
> >  	drm_lastclose(dev);
> >  
> >  	dev->registered = false;
> > +	drm_device_set_plug_state(dev, false);
> >  
> >  	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..fc73e24 100644
> > --- a/drivers/gpu/drm/udl/udl_drv.c
> > +++ b/drivers/gpu/drm/udl/udl_drv.c
> > @@ -108,7 +108,8 @@ 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);
> > +	drm_dev_unref(dev);
> >  }
> >  
> >  /*
> > diff --git a/include/drm/drmP.h b/include/drm/drmP.h
> > index 3bfafcd..980a204 100644
> > --- a/include/drm/drmP.h
> > +++ b/include/drm/drmP.h
> > @@ -488,12 +488,6 @@ 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)
> > -{
> > -	smp_wmb();
> > -	atomic_set(&dev->unplugged, 1);
> > -}
> > -
> >  static inline int drm_device_is_unplugged(struct drm_device *dev)
> >  {
> >  	int ret = atomic_read(&dev->unplugged);
> > diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h
> > index 0fefc3f..eb63078 100644
> > --- a/include/drm/drm_drv.h
> > +++ b/include/drm/drm_drv.h
> > @@ -544,7 +544,6 @@ void drm_dev_unregister(struct drm_device *dev);
> >  void drm_dev_ref(struct drm_device *dev);
> >  void drm_dev_unref(struct drm_device *dev);
> >  void drm_put_dev(struct drm_device *dev);
> > -void drm_unplug_dev(struct drm_device *dev);
> >  
> >  int drm_dev_set_unique(struct drm_device *dev, const char *name);

-- 
Chris Wilson, Intel Open Source Technology Centre

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#1652716

FromMarco Diego Aurélio Mesquita <marcodiegomesquita@gmail.com>
Date2017-05-29 23:20 +0200
Message-ID<tMAf0-5J1-21@gated-at.bofh.it>
In reply to#1652707
On Mon, May 29, 2017 at 5:25 PM, Chris Wilson <chris@chris-wilson.co.uk> wrote:
> convince us to look into this patch again?
> -Chris
>
>> >
>> >  drivers/gpu/drm/drm_drv.c     | 26 ++++++++++----------------
>> >  drivers/gpu/drm/udl/udl_drv.c |  3 ++-
>> >  include/drm/drmP.h            |  6 ------
>> >  include/drm/drm_drv.h         |  1 -
>> >  4 files changed, 12 insertions(+), 24 deletions(-)
>> >
>> > diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
>> > index b5c6bb4..e1da4d1 100644
>> > --- a/drivers/gpu/drm/drm_drv.c
>> > +++ b/drivers/gpu/drm/drm_drv.c
>> > @@ -355,22 +355,6 @@ void drm_put_dev(struct drm_device *dev)
>> >  }
>> >  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);
>> > -
>> > -   if (dev->open_count == 0) {
>> > -           drm_put_dev(dev);
>> > -   }
>> > -   mutex_unlock(&drm_global_mutex);
>> > -}
>> > -EXPORT_SYMBOL(drm_unplug_dev);
>> > -
>> >  /*
>> >   * DRM internal mount
>> >   * We want to be able to allocate our own "struct address_space" to control
>> > @@ -733,6 +717,13 @@ static void remove_compat_control_link(struct drm_device *dev)
>> >     kfree(name);
>> >  }
>> >
>> > +static inline void drm_device_set_plug_state(struct drm_device *dev,
>> > +                                        bool plugged)
>> > +{
>> > +   smp_wmb();
>> > +   atomic_set(&dev->unplugged, !plugged);
>> > +}
>> > +
>> >  /**
>> >   * drm_dev_register - Register DRM device
>> >   * @dev: Device to register
>> > @@ -787,6 +778,8 @@ 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 +819,7 @@ void drm_dev_unregister(struct drm_device *dev)
>> >     drm_lastclose(dev);
>> >
>> >     dev->registered = false;
>> > +   drm_device_set_plug_state(dev, false);
>> >
>> >     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..fc73e24 100644
>> > --- a/drivers/gpu/drm/udl/udl_drv.c
>> > +++ b/drivers/gpu/drm/udl/udl_drv.c
>> > @@ -108,7 +108,8 @@ 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);
>> > +   drm_dev_unref(dev);
>> >  }
>> >
>> >  /*
>> > diff --git a/include/drm/drmP.h b/include/drm/drmP.h
>> > index 3bfafcd..980a204 100644
>> > --- a/include/drm/drmP.h
>> > +++ b/include/drm/drmP.h
>> > @@ -488,12 +488,6 @@ 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)
>> > -{
>> > -   smp_wmb();
>> > -   atomic_set(&dev->unplugged, 1);
>> > -}
>> > -
>> >  static inline int drm_device_is_unplugged(struct drm_device *dev)
>> >  {
>> >     int ret = atomic_read(&dev->unplugged);
>> > diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h
>> > index 0fefc3f..eb63078 100644
>> > --- a/include/drm/drm_drv.h
>> > +++ b/include/drm/drm_drv.h
>> > @@ -544,7 +544,6 @@ void drm_dev_unregister(struct drm_device *dev);
>> >  void drm_dev_ref(struct drm_device *dev);
>> >  void drm_dev_unref(struct drm_device *dev);
>> >  void drm_put_dev(struct drm_device *dev);
>> > -void drm_unplug_dev(struct drm_device *dev);
>> >
>> >  int drm_dev_set_unique(struct drm_device *dev, const char *name);
>

I have no experience writing drivers. So, feel free to disregard my
suggestion if it does not makes sense. I'm trying to update a driver
for a USB device and Hans is helping me with it. I had some problems
when plugging and unplugging the device and ended finding Jeffy's
patch. I made the same changes to the driver I was working on and it
behaved a bit better. When I told Hans about it, he found the problem
with the calls in drm_release.

I'm not sure what is the best way to fix/improve the situation but,
wouldn't it be a good idea to guard dangerous calls like unregister or
unplug so that there are no side effects if they are called more times
then they should? I mean, if a driver does so, it is already broken,
but I think that keeping the kernel safe is a better choice, no?

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#1652875

FromHans de Goede <hdegoede@redhat.com>
Date2017-05-30 09:10 +0200
Message-ID<tMJrX-44F-13@gated-at.bofh.it>
In reply to#1652707
Hi,

On 29-05-17 22:25, Chris Wilson wrote:
> On Fri, Apr 14, 2017 at 11:15:04AM -0400, Sean Paul wrote:
>> On Thu, Apr 13, 2017 at 03:32:44PM +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.
>>>
>>> Also drop drm_unplug_dev, because it would be unused after other changes.
>>>
>>> Verified on rk3399 chromebook kevin(with cros 4.4 kernel), no more crashes
>>> when unbinding drm with ui service still running.
>>>
>>> v2: Fix some commit messages.
>>> v3: Reuse unplug status.
>>> v4: Add drm_device_set_plug_state helper.
>>> v5: Fix hang when unregistering drm dev with open_count 0.
>>> v6: Move drm_device_set_plug_state into drm_drv.
>>> v7: Add missing drm_dev_unref in udl_drv.
>>> v8: Fix compiler errors after enable udl.
>>>
>>> Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
>>>
>>> ---
>>
>> Hi Jeffy,
>> Given the trouble we've had with this patch already, coupled with the fact that
>> unbinding while userspace is active is a contrived/pathological case, I don't
>> think it's worth picking this patch upstream.
>>
>> If it's really causing issues downstream, you can add my Reviewed-by for a CHROMIUM
>> patch, but I'd rather not carry patches in the CrOS repo if we don't need to.
> 
> Would a
> 
> Fixes: a39be606f99d ("drm: Do a full device unregister when unplugging")
> Reported-by: Marco Diego Aurélio Mesquita <marcodiegomesquita@gmail.com>
> Cc: Hans de Goede <hdegoede@redhat.com>
> 
> convince us to look into this patch again?

The problem is this patch is wrong, see below.

>>>   drivers/gpu/drm/drm_drv.c     | 26 ++++++++++----------------
>>>   drivers/gpu/drm/udl/udl_drv.c |  3 ++-
>>>   include/drm/drmP.h            |  6 ------
>>>   include/drm/drm_drv.h         |  1 -
>>>   4 files changed, 12 insertions(+), 24 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
>>> index b5c6bb4..e1da4d1 100644
>>> --- a/drivers/gpu/drm/drm_drv.c
>>> +++ b/drivers/gpu/drm/drm_drv.c
>>> @@ -355,22 +355,6 @@ void drm_put_dev(struct drm_device *dev)
>>>   }
>>>   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);
>>> -
>>> -	if (dev->open_count == 0) {
>>> -		drm_put_dev(dev);
>>> -	}
>>> -	mutex_unlock(&drm_global_mutex);
>>> -}
>>> -EXPORT_SYMBOL(drm_unplug_dev);
>>> -
>>>   /*
>>>    * DRM internal mount
>>>    * We want to be able to allocate our own "struct address_space" to control
>>> @@ -733,6 +717,13 @@ static void remove_compat_control_link(struct drm_device *dev)
>>>   	kfree(name);
>>>   }
>>>   
>>> +static inline void drm_device_set_plug_state(struct drm_device *dev,
>>> +					     bool plugged)
>>> +{
>>> +	smp_wmb();
>>> +	atomic_set(&dev->unplugged, !plugged);
>>> +}
>>> +
>>>   /**
>>>    * drm_dev_register - Register DRM device
>>>    * @dev: Device to register
>>> @@ -787,6 +778,8 @@ 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 +819,7 @@ void drm_dev_unregister(struct drm_device *dev)
>>>   	drm_lastclose(dev);
>>>   
>>>   	dev->registered = false;
>>> +	drm_device_set_plug_state(dev, false);
>>>   
>>>   	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..fc73e24 100644
>>> --- a/drivers/gpu/drm/udl/udl_drv.c
>>> +++ b/drivers/gpu/drm/udl/udl_drv.c
>>> @@ -108,7 +108,8 @@ 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);
>>> +	drm_dev_unref(dev);

The unref here will cause the device struct to get free-ed even if
userspace still holds references to it through the drm_dev. To fix
this we would need to call drm_dev_ref on a open from userspace and
drm_dev_unref from drm_release.

Regards,

Hans




>>>   }
>>>   
>>>   /*
>>> diff --git a/include/drm/drmP.h b/include/drm/drmP.h
>>> index 3bfafcd..980a204 100644
>>> --- a/include/drm/drmP.h
>>> +++ b/include/drm/drmP.h
>>> @@ -488,12 +488,6 @@ 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)
>>> -{
>>> -	smp_wmb();
>>> -	atomic_set(&dev->unplugged, 1);
>>> -}
>>> -
>>>   static inline int drm_device_is_unplugged(struct drm_device *dev)
>>>   {
>>>   	int ret = atomic_read(&dev->unplugged);
>>> diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h
>>> index 0fefc3f..eb63078 100644
>>> --- a/include/drm/drm_drv.h
>>> +++ b/include/drm/drm_drv.h
>>> @@ -544,7 +544,6 @@ void drm_dev_unregister(struct drm_device *dev);
>>>   void drm_dev_ref(struct drm_device *dev);
>>>   void drm_dev_unref(struct drm_device *dev);
>>>   void drm_put_dev(struct drm_device *dev);
>>> -void drm_unplug_dev(struct drm_device *dev);
>>>   
>>>   int drm_dev_set_unique(struct drm_device *dev, const char *name);
>

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#1653793

Fromjeffy <jeffy.chen@rock-chips.com>
Date2017-05-31 04:50 +0200
Message-ID<tN1RT-7cZ-5@gated-at.bofh.it>
In reply to#1652875
Hi Hans,

thanx for investigating :)

On 05/30/2017 03:06 PM, Hans de Goede wrote:
> Hi,
>
> On 29-05-17 22:25, Chris Wilson wrote:
>> On Fri, Apr 14, 2017 at 11:15:04AM -0400, Sean Paul wrote:
>>> On Thu, Apr 13, 2017 at 03:32:44PM +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.
>>>>
>>>> Also drop drm_unplug_dev, because it would be unused after other
>>>> changes.
>>>>
>>>> Verified on rk3399 chromebook kevin(with cros 4.4 kernel), no more
>>>> crashes
>>>> when unbinding drm with ui service still running.
>>>>
>>>> v2: Fix some commit messages.
>>>> v3: Reuse unplug status.
>>>> v4: Add drm_device_set_plug_state helper.
>>>> v5: Fix hang when unregistering drm dev with open_count 0.
>>>> v6: Move drm_device_set_plug_state into drm_drv.
>>>> v7: Add missing drm_dev_unref in udl_drv.
>>>> v8: Fix compiler errors after enable udl.
>>>>
>>>> Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
>>>>
>>>> ---
>>>
>>> Hi Jeffy,
>>> Given the trouble we've had with this patch already, coupled with the
>>> fact that
>>> unbinding while userspace is active is a contrived/pathological case,
>>> I don't
>>> think it's worth picking this patch upstream.
>>>
>>> If it's really causing issues downstream, you can add my Reviewed-by
>>> for a CHROMIUM
>>> patch, but I'd rather not carry patches in the CrOS repo if we don't
>>> need to.
>>
>> Would a
>>
>> Fixes: a39be606f99d ("drm: Do a full device unregister when unplugging")
>> Reported-by: Marco Diego Aurélio Mesquita <marcodiegomesquita@gmail.com>
>> Cc: Hans de Goede <hdegoede@redhat.com>
>>
>> convince us to look into this patch again?
>
> The problem is this patch is wrong, see below.
>
>>>>   drivers/gpu/drm/drm_drv.c     | 26 ++++++++++----------------
>>>>   drivers/gpu/drm/udl/udl_drv.c |  3 ++-
>>>>   include/drm/drmP.h            |  6 ------
>>>>   include/drm/drm_drv.h         |  1 -
>>>>   4 files changed, 12 insertions(+), 24 deletions(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
>>>> index b5c6bb4..e1da4d1 100644
>>>> --- a/drivers/gpu/drm/drm_drv.c
>>>> +++ b/drivers/gpu/drm/drm_drv.c
>>>> @@ -355,22 +355,6 @@ void drm_put_dev(struct drm_device *dev)
>>>>   }
>>>>   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);
>>>> -
>>>> -    if (dev->open_count == 0) {
>>>> -        drm_put_dev(dev);
>>>> -    }
>>>> -    mutex_unlock(&drm_global_mutex);
>>>> -}
>>>> -EXPORT_SYMBOL(drm_unplug_dev);
>>>> -
>>>>   /*
>>>>    * DRM internal mount
>>>>    * We want to be able to allocate our own "struct address_space"
>>>> to control
>>>> @@ -733,6 +717,13 @@ static void remove_compat_control_link(struct
>>>> drm_device *dev)
>>>>       kfree(name);
>>>>   }
>>>> +static inline void drm_device_set_plug_state(struct drm_device *dev,
>>>> +                         bool plugged)
>>>> +{
>>>> +    smp_wmb();
>>>> +    atomic_set(&dev->unplugged, !plugged);
>>>> +}
>>>> +
>>>>   /**
>>>>    * drm_dev_register - Register DRM device
>>>>    * @dev: Device to register
>>>> @@ -787,6 +778,8 @@ 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 +819,7 @@ void drm_dev_unregister(struct drm_device *dev)
>>>>       drm_lastclose(dev);
>>>>       dev->registered = false;
>>>> +    drm_device_set_plug_state(dev, false);
>>>>       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..fc73e24 100644
>>>> --- a/drivers/gpu/drm/udl/udl_drv.c
>>>> +++ b/drivers/gpu/drm/udl/udl_drv.c
>>>> @@ -108,7 +108,8 @@ 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);
>>>> +    drm_dev_unref(dev);
>
> The unref here will cause the device struct to get free-ed even if
> userspace still holds references to it through the drm_dev. To fix
> this we would need to call drm_dev_ref on a open from userspace and
> drm_dev_unref from drm_release.

right, but i think we are already did the ref/unref in the open/release 
through drm_minor_acquire/drm_minor_release.

i think the problem would be:
1/ we are trying to unregister&unref when disconnected

2/ the drm_release would try to unregister&unref(by calling drm_put_dev) 
when found it unplugged.

and your patch "drm: Do not call drm_dev_unregister twice on 
drm_unplug_dev" looks like a good way to fix this(to me), maybe we can 
place this patch after yours, and check for open_count here?

-    drm_unplug_dev(dev);
+    if (dev->open_count == 0)
+        drm_dev_unref(dev);


>
> Regards,
>
> Hans
>
>
>
>
>>>>   }
>>>>   /*
>>>> diff --git a/include/drm/drmP.h b/include/drm/drmP.h
>>>> index 3bfafcd..980a204 100644
>>>> --- a/include/drm/drmP.h
>>>> +++ b/include/drm/drmP.h
>>>> @@ -488,12 +488,6 @@ 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)
>>>> -{
>>>> -    smp_wmb();
>>>> -    atomic_set(&dev->unplugged, 1);
>>>> -}
>>>> -
>>>>   static inline int drm_device_is_unplugged(struct drm_device *dev)
>>>>   {
>>>>       int ret = atomic_read(&dev->unplugged);
>>>> diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h
>>>> index 0fefc3f..eb63078 100644
>>>> --- a/include/drm/drm_drv.h
>>>> +++ b/include/drm/drm_drv.h
>>>> @@ -544,7 +544,6 @@ void drm_dev_unregister(struct drm_device *dev);
>>>>   void drm_dev_ref(struct drm_device *dev);
>>>>   void drm_dev_unref(struct drm_device *dev);
>>>>   void drm_put_dev(struct drm_device *dev);
>>>> -void drm_unplug_dev(struct drm_device *dev);
>>>>   int drm_dev_set_unique(struct drm_device *dev, const char *name);
>>
>
>
>

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#1655082

FromHans de Goede <hdegoede@redhat.com>
Date2017-06-01 14:20 +0200
Message-ID<tNxf4-2qB-19@gated-at.bofh.it>
In reply to#1653793
Hi,

On 31-05-17 04:39, jeffy wrote:
> Hi Hans,
> 
> thanx for investigating :)
> 
> On 05/30/2017 03:06 PM, Hans de Goede wrote:
>> Hi,
>>
>> On 29-05-17 22:25, Chris Wilson wrote:
>>> On Fri, Apr 14, 2017 at 11:15:04AM -0400, Sean Paul wrote:
>>>> On Thu, Apr 13, 2017 at 03:32:44PM +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.
>>>>>
>>>>> Also drop drm_unplug_dev, because it would be unused after other
>>>>> changes.
>>>>>
>>>>> Verified on rk3399 chromebook kevin(with cros 4.4 kernel), no more
>>>>> crashes
>>>>> when unbinding drm with ui service still running.
>>>>>
>>>>> v2: Fix some commit messages.
>>>>> v3: Reuse unplug status.
>>>>> v4: Add drm_device_set_plug_state helper.
>>>>> v5: Fix hang when unregistering drm dev with open_count 0.
>>>>> v6: Move drm_device_set_plug_state into drm_drv.
>>>>> v7: Add missing drm_dev_unref in udl_drv.
>>>>> v8: Fix compiler errors after enable udl.
>>>>>
>>>>> Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
>>>>>
>>>>> ---
>>>>
>>>> Hi Jeffy,
>>>> Given the trouble we've had with this patch already, coupled with the
>>>> fact that
>>>> unbinding while userspace is active is a contrived/pathological case,
>>>> I don't
>>>> think it's worth picking this patch upstream.
>>>>
>>>> If it's really causing issues downstream, you can add my Reviewed-by
>>>> for a CHROMIUM
>>>> patch, but I'd rather not carry patches in the CrOS repo if we don't
>>>> need to.
>>>
>>> Would a
>>>
>>> Fixes: a39be606f99d ("drm: Do a full device unregister when unplugging")
>>> Reported-by: Marco Diego Aurélio Mesquita <marcodiegomesquita@gmail.com>
>>> Cc: Hans de Goede <hdegoede@redhat.com>
>>>
>>> convince us to look into this patch again?
>>
>> The problem is this patch is wrong, see below.
>>
>>>>>   drivers/gpu/drm/drm_drv.c     | 26 ++++++++++----------------
>>>>>   drivers/gpu/drm/udl/udl_drv.c |  3 ++-
>>>>>   include/drm/drmP.h            |  6 ------
>>>>>   include/drm/drm_drv.h         |  1 -
>>>>>   4 files changed, 12 insertions(+), 24 deletions(-)
>>>>>
>>>>> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
>>>>> index b5c6bb4..e1da4d1 100644
>>>>> --- a/drivers/gpu/drm/drm_drv.c
>>>>> +++ b/drivers/gpu/drm/drm_drv.c
>>>>> @@ -355,22 +355,6 @@ void drm_put_dev(struct drm_device *dev)
>>>>>   }
>>>>>   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);
>>>>> -
>>>>> -    if (dev->open_count == 0) {
>>>>> -        drm_put_dev(dev);
>>>>> -    }
>>>>> -    mutex_unlock(&drm_global_mutex);
>>>>> -}
>>>>> -EXPORT_SYMBOL(drm_unplug_dev);
>>>>> -
>>>>>   /*
>>>>>    * DRM internal mount
>>>>>    * We want to be able to allocate our own "struct address_space"
>>>>> to control
>>>>> @@ -733,6 +717,13 @@ static void remove_compat_control_link(struct
>>>>> drm_device *dev)
>>>>>       kfree(name);
>>>>>   }
>>>>> +static inline void drm_device_set_plug_state(struct drm_device *dev,
>>>>> +                         bool plugged)
>>>>> +{
>>>>> +    smp_wmb();
>>>>> +    atomic_set(&dev->unplugged, !plugged);
>>>>> +}
>>>>> +
>>>>>   /**
>>>>>    * drm_dev_register - Register DRM device
>>>>>    * @dev: Device to register
>>>>> @@ -787,6 +778,8 @@ 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 +819,7 @@ void drm_dev_unregister(struct drm_device *dev)
>>>>>       drm_lastclose(dev);
>>>>>       dev->registered = false;
>>>>> +    drm_device_set_plug_state(dev, false);
>>>>>       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..fc73e24 100644
>>>>> --- a/drivers/gpu/drm/udl/udl_drv.c
>>>>> +++ b/drivers/gpu/drm/udl/udl_drv.c
>>>>> @@ -108,7 +108,8 @@ 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);
>>>>> +    drm_dev_unref(dev);
>>
>> The unref here will cause the device struct to get free-ed even if
>> userspace still holds references to it through the drm_dev. To fix
>> this we would need to call drm_dev_ref on a open from userspace and
>> drm_dev_unref from drm_release.
> 
> right, but i think we are already did the ref/unref in the open/release through drm_minor_acquire/drm_minor_release.

Ah yes, I see. Still calling drm_dev_unregister() directly from
udl_usb_disconnect() is not going to work, see the patch titled
"drm: Fix oops + Xserver hang when unplugging USB drm devices"

The problem is that drm_dev_unregister() probably should be
split into a drm_dev_unregister() and drm_dev_cleanup()
function with the cleanup part getting called by the last unref,
and at least calling drm_lastclose and the driver->unload call
needs to be moved to the new drm_dev_cleanup.

However splitting drm_dev_unregister() into drm_dev_unregister()
and drm_dev_cleanup() is easier said then done because that
would change the teardown order (e.g. calling driver->unload
later) which may very well cause problems in various places
and drivers.

Regards,

Hans



>>>>>   }
>>>>>   /*
>>>>> diff --git a/include/drm/drmP.h b/include/drm/drmP.h
>>>>> index 3bfafcd..980a204 100644
>>>>> --- a/include/drm/drmP.h
>>>>> +++ b/include/drm/drmP.h
>>>>> @@ -488,12 +488,6 @@ 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)
>>>>> -{
>>>>> -    smp_wmb();
>>>>> -    atomic_set(&dev->unplugged, 1);
>>>>> -}
>>>>> -
>>>>>   static inline int drm_device_is_unplugged(struct drm_device *dev)
>>>>>   {
>>>>>       int ret = atomic_read(&dev->unplugged);
>>>>> diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h
>>>>> index 0fefc3f..eb63078 100644
>>>>> --- a/include/drm/drm_drv.h
>>>>> +++ b/include/drm/drm_drv.h
>>>>> @@ -544,7 +544,6 @@ void drm_dev_unregister(struct drm_device *dev);
>>>>>   void drm_dev_ref(struct drm_device *dev);
>>>>>   void drm_dev_unref(struct drm_device *dev);
>>>>>   void drm_put_dev(struct drm_device *dev);
>>>>> -void drm_unplug_dev(struct drm_device *dev);
>>>>>   int drm_dev_set_unique(struct drm_device *dev, const char *name);
>>>
>>
>>
>>
> 
>

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#1655087

FromHans de Goede <hdegoede@redhat.com>
Date2017-06-01 14:30 +0200
Message-ID<tNxoK-2tN-13@gated-at.bofh.it>
In reply to#1655082
Hi,

On 01-06-17 14:22, Chris Wilson wrote:
> On Thu, Jun 01, 2017 at 02:13:28PM +0200, Hans de Goede wrote:
>> Hi,
>>
>> On 31-05-17 04:39, jeffy wrote:
>>> Hi Hans,
>>>
>>> thanx for investigating :)
>>>
>>> On 05/30/2017 03:06 PM, Hans de Goede wrote:
>>>> Hi,
>>>>
>>>> On 29-05-17 22:25, Chris Wilson wrote:
>>>>> On Fri, Apr 14, 2017 at 11:15:04AM -0400, Sean Paul wrote:
>>>>>> On Thu, Apr 13, 2017 at 03:32:44PM +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.
>>>>>>>
>>>>>>> Also drop drm_unplug_dev, because it would be unused after other
>>>>>>> changes.
>>>>>>>
>>>>>>> Verified on rk3399 chromebook kevin(with cros 4.4 kernel), no more
>>>>>>> crashes
>>>>>>> when unbinding drm with ui service still running.
>>>>>>>
>>>>>>> v2: Fix some commit messages.
>>>>>>> v3: Reuse unplug status.
>>>>>>> v4: Add drm_device_set_plug_state helper.
>>>>>>> v5: Fix hang when unregistering drm dev with open_count 0.
>>>>>>> v6: Move drm_device_set_plug_state into drm_drv.
>>>>>>> v7: Add missing drm_dev_unref in udl_drv.
>>>>>>> v8: Fix compiler errors after enable udl.
>>>>>>>
>>>>>>> Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
>>>>>>>
>>>>>>> ---
>>>>>>
>>>>>> Hi Jeffy,
>>>>>> Given the trouble we've had with this patch already, coupled with the
>>>>>> fact that
>>>>>> unbinding while userspace is active is a contrived/pathological case,
>>>>>> I don't
>>>>>> think it's worth picking this patch upstream.
>>>>>>
>>>>>> If it's really causing issues downstream, you can add my Reviewed-by
>>>>>> for a CHROMIUM
>>>>>> patch, but I'd rather not carry patches in the CrOS repo if we don't
>>>>>> need to.
>>>>>
>>>>> Would a
>>>>>
>>>>> Fixes: a39be606f99d ("drm: Do a full device unregister when unplugging")
>>>>> Reported-by: Marco Diego Aurélio Mesquita <marcodiegomesquita@gmail.com>
>>>>> Cc: Hans de Goede <hdegoede@redhat.com>
>>>>>
>>>>> convince us to look into this patch again?
>>>>
>>>> The problem is this patch is wrong, see below.
>>>>
>>>>>>>   drivers/gpu/drm/drm_drv.c     | 26 ++++++++++----------------
>>>>>>>   drivers/gpu/drm/udl/udl_drv.c |  3 ++-
>>>>>>>   include/drm/drmP.h            |  6 ------
>>>>>>>   include/drm/drm_drv.h         |  1 -
>>>>>>>   4 files changed, 12 insertions(+), 24 deletions(-)
>>>>>>>
>>>>>>> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
>>>>>>> index b5c6bb4..e1da4d1 100644
>>>>>>> --- a/drivers/gpu/drm/drm_drv.c
>>>>>>> +++ b/drivers/gpu/drm/drm_drv.c
>>>>>>> @@ -355,22 +355,6 @@ void drm_put_dev(struct drm_device *dev)
>>>>>>>   }
>>>>>>>   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);
>>>>>>> -
>>>>>>> -    if (dev->open_count == 0) {
>>>>>>> -        drm_put_dev(dev);
>>>>>>> -    }
>>>>>>> -    mutex_unlock(&drm_global_mutex);
>>>>>>> -}
>>>>>>> -EXPORT_SYMBOL(drm_unplug_dev);
>>>>>>> -
>>>>>>>   /*
>>>>>>>    * DRM internal mount
>>>>>>>    * We want to be able to allocate our own "struct address_space"
>>>>>>> to control
>>>>>>> @@ -733,6 +717,13 @@ static void remove_compat_control_link(struct
>>>>>>> drm_device *dev)
>>>>>>>       kfree(name);
>>>>>>>   }
>>>>>>> +static inline void drm_device_set_plug_state(struct drm_device *dev,
>>>>>>> +                         bool plugged)
>>>>>>> +{
>>>>>>> +    smp_wmb();
>>>>>>> +    atomic_set(&dev->unplugged, !plugged);
>>>>>>> +}
>>>>>>> +
>>>>>>>   /**
>>>>>>>    * drm_dev_register - Register DRM device
>>>>>>>    * @dev: Device to register
>>>>>>> @@ -787,6 +778,8 @@ 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 +819,7 @@ void drm_dev_unregister(struct drm_device *dev)
>>>>>>>       drm_lastclose(dev);
>>>>>>>       dev->registered = false;
>>>>>>> +    drm_device_set_plug_state(dev, false);
>>>>>>>       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..fc73e24 100644
>>>>>>> --- a/drivers/gpu/drm/udl/udl_drv.c
>>>>>>> +++ b/drivers/gpu/drm/udl/udl_drv.c
>>>>>>> @@ -108,7 +108,8 @@ 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);
>>>>>>> +    drm_dev_unref(dev);
>>>>
>>>> The unref here will cause the device struct to get free-ed even if
>>>> userspace still holds references to it through the drm_dev. To fix
>>>> this we would need to call drm_dev_ref on a open from userspace and
>>>> drm_dev_unref from drm_release.
>>>
>>> right, but i think we are already did the ref/unref in the open/release through drm_minor_acquire/drm_minor_release.
>>
>> Ah yes, I see. Still calling drm_dev_unregister() directly from
>> udl_usb_disconnect() is not going to work, see the patch titled
>> "drm: Fix oops + Xserver hang when unplugging USB drm devices"
>>
>> The problem is that drm_dev_unregister() probably should be
>> split into a drm_dev_unregister() and drm_dev_cleanup()
>> function with the cleanup part getting called by the last unref,
>> and at least calling drm_lastclose and the driver->unload call
>> needs to be moved to the new drm_dev_cleanup.
> 
> It already is. driver->unload() has been deprecated for a while, in
> spirit at least, we probably should add a warning to it, and is
> not meant to be used anymore.

Ok, what about drm_lastclose ? Calling that while userspace still
has fds open seems wrong too. Same for this part of drm_dev_unregister():

         list_for_each_entry_safe(r_list, list_temp, &dev->maplist, head)
                 drm_legacy_rmmap(dev, r_list->map);

Removing mmapping backing data (if I understand correctly) while
it may still be used seems like a bad idea too, so I do believe that
drm_dev_unregister needs some love / some bits moved to the last
drm_dev_put call before it will be safe to call it directly
on usb-disconnect.

Regards,

Hans

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#1655122

FromChris Wilson <chris@chris-wilson.co.uk>
Date2017-06-01 15:10 +0200
Message-ID<tNy1s-2YH-11@gated-at.bofh.it>
In reply to#1655087
On Thu, Jun 01, 2017 at 02:26:01PM +0200, Hans de Goede wrote:
> Hi,
> 
> On 01-06-17 14:22, Chris Wilson wrote:
> >On Thu, Jun 01, 2017 at 02:13:28PM +0200, Hans de Goede wrote:
> >>Hi,
> >>
> >>On 31-05-17 04:39, jeffy wrote:
> >>>Hi Hans,
> >>>
> >>>thanx for investigating :)
> >>>
> >>>On 05/30/2017 03:06 PM, Hans de Goede wrote:
> >>>>Hi,
> >>>>
> >>>>On 29-05-17 22:25, Chris Wilson wrote:
> >>>>>On Fri, Apr 14, 2017 at 11:15:04AM -0400, Sean Paul wrote:
> >>>>>>On Thu, Apr 13, 2017 at 03:32:44PM +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.
> >>>>>>>
> >>>>>>>Also drop drm_unplug_dev, because it would be unused after other
> >>>>>>>changes.
> >>>>>>>
> >>>>>>>Verified on rk3399 chromebook kevin(with cros 4.4 kernel), no more
> >>>>>>>crashes
> >>>>>>>when unbinding drm with ui service still running.
> >>>>>>>
> >>>>>>>v2: Fix some commit messages.
> >>>>>>>v3: Reuse unplug status.
> >>>>>>>v4: Add drm_device_set_plug_state helper.
> >>>>>>>v5: Fix hang when unregistering drm dev with open_count 0.
> >>>>>>>v6: Move drm_device_set_plug_state into drm_drv.
> >>>>>>>v7: Add missing drm_dev_unref in udl_drv.
> >>>>>>>v8: Fix compiler errors after enable udl.
> >>>>>>>
> >>>>>>>Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
> >>>>>>>
> >>>>>>>---
> >>>>>>
> >>>>>>Hi Jeffy,
> >>>>>>Given the trouble we've had with this patch already, coupled with the
> >>>>>>fact that
> >>>>>>unbinding while userspace is active is a contrived/pathological case,
> >>>>>>I don't
> >>>>>>think it's worth picking this patch upstream.
> >>>>>>
> >>>>>>If it's really causing issues downstream, you can add my Reviewed-by
> >>>>>>for a CHROMIUM
> >>>>>>patch, but I'd rather not carry patches in the CrOS repo if we don't
> >>>>>>need to.
> >>>>>
> >>>>>Would a
> >>>>>
> >>>>>Fixes: a39be606f99d ("drm: Do a full device unregister when unplugging")
> >>>>>Reported-by: Marco Diego Aurélio Mesquita <marcodiegomesquita@gmail.com>
> >>>>>Cc: Hans de Goede <hdegoede@redhat.com>
> >>>>>
> >>>>>convince us to look into this patch again?
> >>>>
> >>>>The problem is this patch is wrong, see below.
> >>>>
> >>>>>>>  drivers/gpu/drm/drm_drv.c     | 26 ++++++++++----------------
> >>>>>>>  drivers/gpu/drm/udl/udl_drv.c |  3 ++-
> >>>>>>>  include/drm/drmP.h            |  6 ------
> >>>>>>>  include/drm/drm_drv.h         |  1 -
> >>>>>>>  4 files changed, 12 insertions(+), 24 deletions(-)
> >>>>>>>
> >>>>>>>diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
> >>>>>>>index b5c6bb4..e1da4d1 100644
> >>>>>>>--- a/drivers/gpu/drm/drm_drv.c
> >>>>>>>+++ b/drivers/gpu/drm/drm_drv.c
> >>>>>>>@@ -355,22 +355,6 @@ void drm_put_dev(struct drm_device *dev)
> >>>>>>>  }
> >>>>>>>  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);
> >>>>>>>-
> >>>>>>>-    if (dev->open_count == 0) {
> >>>>>>>-        drm_put_dev(dev);
> >>>>>>>-    }
> >>>>>>>-    mutex_unlock(&drm_global_mutex);
> >>>>>>>-}
> >>>>>>>-EXPORT_SYMBOL(drm_unplug_dev);
> >>>>>>>-
> >>>>>>>  /*
> >>>>>>>   * DRM internal mount
> >>>>>>>   * We want to be able to allocate our own "struct address_space"
> >>>>>>>to control
> >>>>>>>@@ -733,6 +717,13 @@ static void remove_compat_control_link(struct
> >>>>>>>drm_device *dev)
> >>>>>>>      kfree(name);
> >>>>>>>  }
> >>>>>>>+static inline void drm_device_set_plug_state(struct drm_device *dev,
> >>>>>>>+                         bool plugged)
> >>>>>>>+{
> >>>>>>>+    smp_wmb();
> >>>>>>>+    atomic_set(&dev->unplugged, !plugged);
> >>>>>>>+}
> >>>>>>>+
> >>>>>>>  /**
> >>>>>>>   * drm_dev_register - Register DRM device
> >>>>>>>   * @dev: Device to register
> >>>>>>>@@ -787,6 +778,8 @@ 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 +819,7 @@ void drm_dev_unregister(struct drm_device *dev)
> >>>>>>>      drm_lastclose(dev);
> >>>>>>>      dev->registered = false;
> >>>>>>>+    drm_device_set_plug_state(dev, false);
> >>>>>>>      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..fc73e24 100644
> >>>>>>>--- a/drivers/gpu/drm/udl/udl_drv.c
> >>>>>>>+++ b/drivers/gpu/drm/udl/udl_drv.c
> >>>>>>>@@ -108,7 +108,8 @@ 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);
> >>>>>>>+    drm_dev_unref(dev);
> >>>>
> >>>>The unref here will cause the device struct to get free-ed even if
> >>>>userspace still holds references to it through the drm_dev. To fix
> >>>>this we would need to call drm_dev_ref on a open from userspace and
> >>>>drm_dev_unref from drm_release.
> >>>
> >>>right, but i think we are already did the ref/unref in the open/release through drm_minor_acquire/drm_minor_release.
> >>
> >>Ah yes, I see. Still calling drm_dev_unregister() directly from
> >>udl_usb_disconnect() is not going to work, see the patch titled
> >>"drm: Fix oops + Xserver hang when unplugging USB drm devices"
> >>
> >>The problem is that drm_dev_unregister() probably should be
> >>split into a drm_dev_unregister() and drm_dev_cleanup()
> >>function with the cleanup part getting called by the last unref,
> >>and at least calling drm_lastclose and the driver->unload call
> >>needs to be moved to the new drm_dev_cleanup.
> >
> >It already is. driver->unload() has been deprecated for a while, in
> >spirit at least, we probably should add a warning to it, and is
> >not meant to be used anymore.
> 
> Ok, what about drm_lastclose ? Calling that while userspace still
> has fds open seems wrong too. Same for this part of drm_dev_unregister():

lastclose should not be a part of unregister, or it is spectacularly
misnamed.

>         list_for_each_entry_safe(r_list, list_temp, &dev->maplist, head)
>                 drm_legacy_rmmap(dev, r_list->map);

Just give Daniel some more fuel for killing legacy, he'll be thankful.
> 
> Removing mmapping backing data (if I understand correctly) while
> it may still be used seems like a bad idea too, so I do believe that
> drm_dev_unregister needs some love / some bits moved to the last
> drm_dev_put call before it will be safe to call it directly
> on usb-disconnect.

True, it needs more love, and the usb devices are the best test cases
for this unless we write some hw independent selftests.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre

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#1655091

FromChris Wilson <chris@chris-wilson.co.uk>
Date2017-06-01 14:30 +0200
Message-ID<tNxoK-2tN-15@gated-at.bofh.it>
In reply to#1655082
On Thu, Jun 01, 2017 at 02:13:28PM +0200, Hans de Goede wrote:
> Hi,
> 
> On 31-05-17 04:39, jeffy wrote:
> >Hi Hans,
> >
> >thanx for investigating :)
> >
> >On 05/30/2017 03:06 PM, Hans de Goede wrote:
> >>Hi,
> >>
> >>On 29-05-17 22:25, Chris Wilson wrote:
> >>>On Fri, Apr 14, 2017 at 11:15:04AM -0400, Sean Paul wrote:
> >>>>On Thu, Apr 13, 2017 at 03:32:44PM +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.
> >>>>>
> >>>>>Also drop drm_unplug_dev, because it would be unused after other
> >>>>>changes.
> >>>>>
> >>>>>Verified on rk3399 chromebook kevin(with cros 4.4 kernel), no more
> >>>>>crashes
> >>>>>when unbinding drm with ui service still running.
> >>>>>
> >>>>>v2: Fix some commit messages.
> >>>>>v3: Reuse unplug status.
> >>>>>v4: Add drm_device_set_plug_state helper.
> >>>>>v5: Fix hang when unregistering drm dev with open_count 0.
> >>>>>v6: Move drm_device_set_plug_state into drm_drv.
> >>>>>v7: Add missing drm_dev_unref in udl_drv.
> >>>>>v8: Fix compiler errors after enable udl.
> >>>>>
> >>>>>Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
> >>>>>
> >>>>>---
> >>>>
> >>>>Hi Jeffy,
> >>>>Given the trouble we've had with this patch already, coupled with the
> >>>>fact that
> >>>>unbinding while userspace is active is a contrived/pathological case,
> >>>>I don't
> >>>>think it's worth picking this patch upstream.
> >>>>
> >>>>If it's really causing issues downstream, you can add my Reviewed-by
> >>>>for a CHROMIUM
> >>>>patch, but I'd rather not carry patches in the CrOS repo if we don't
> >>>>need to.
> >>>
> >>>Would a
> >>>
> >>>Fixes: a39be606f99d ("drm: Do a full device unregister when unplugging")
> >>>Reported-by: Marco Diego Aurélio Mesquita <marcodiegomesquita@gmail.com>
> >>>Cc: Hans de Goede <hdegoede@redhat.com>
> >>>
> >>>convince us to look into this patch again?
> >>
> >>The problem is this patch is wrong, see below.
> >>
> >>>>>  drivers/gpu/drm/drm_drv.c     | 26 ++++++++++----------------
> >>>>>  drivers/gpu/drm/udl/udl_drv.c |  3 ++-
> >>>>>  include/drm/drmP.h            |  6 ------
> >>>>>  include/drm/drm_drv.h         |  1 -
> >>>>>  4 files changed, 12 insertions(+), 24 deletions(-)
> >>>>>
> >>>>>diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
> >>>>>index b5c6bb4..e1da4d1 100644
> >>>>>--- a/drivers/gpu/drm/drm_drv.c
> >>>>>+++ b/drivers/gpu/drm/drm_drv.c
> >>>>>@@ -355,22 +355,6 @@ void drm_put_dev(struct drm_device *dev)
> >>>>>  }
> >>>>>  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);
> >>>>>-
> >>>>>-    if (dev->open_count == 0) {
> >>>>>-        drm_put_dev(dev);
> >>>>>-    }
> >>>>>-    mutex_unlock(&drm_global_mutex);
> >>>>>-}
> >>>>>-EXPORT_SYMBOL(drm_unplug_dev);
> >>>>>-
> >>>>>  /*
> >>>>>   * DRM internal mount
> >>>>>   * We want to be able to allocate our own "struct address_space"
> >>>>>to control
> >>>>>@@ -733,6 +717,13 @@ static void remove_compat_control_link(struct
> >>>>>drm_device *dev)
> >>>>>      kfree(name);
> >>>>>  }
> >>>>>+static inline void drm_device_set_plug_state(struct drm_device *dev,
> >>>>>+                         bool plugged)
> >>>>>+{
> >>>>>+    smp_wmb();
> >>>>>+    atomic_set(&dev->unplugged, !plugged);
> >>>>>+}
> >>>>>+
> >>>>>  /**
> >>>>>   * drm_dev_register - Register DRM device
> >>>>>   * @dev: Device to register
> >>>>>@@ -787,6 +778,8 @@ 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 +819,7 @@ void drm_dev_unregister(struct drm_device *dev)
> >>>>>      drm_lastclose(dev);
> >>>>>      dev->registered = false;
> >>>>>+    drm_device_set_plug_state(dev, false);
> >>>>>      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..fc73e24 100644
> >>>>>--- a/drivers/gpu/drm/udl/udl_drv.c
> >>>>>+++ b/drivers/gpu/drm/udl/udl_drv.c
> >>>>>@@ -108,7 +108,8 @@ 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);
> >>>>>+    drm_dev_unref(dev);
> >>
> >>The unref here will cause the device struct to get free-ed even if
> >>userspace still holds references to it through the drm_dev. To fix
> >>this we would need to call drm_dev_ref on a open from userspace and
> >>drm_dev_unref from drm_release.
> >
> >right, but i think we are already did the ref/unref in the open/release through drm_minor_acquire/drm_minor_release.
> 
> Ah yes, I see. Still calling drm_dev_unregister() directly from
> udl_usb_disconnect() is not going to work, see the patch titled
> "drm: Fix oops + Xserver hang when unplugging USB drm devices"
> 
> The problem is that drm_dev_unregister() probably should be
> split into a drm_dev_unregister() and drm_dev_cleanup()
> function with the cleanup part getting called by the last unref,
> and at least calling drm_lastclose and the driver->unload call
> needs to be moved to the new drm_dev_cleanup.

It already is. driver->unload() has been deprecated for a while, in
spirit at least, we probably should add a warning to it, and is
not meant to be used anymore.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre

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