linux-kernel - Re: [PATCH v8 1/2] drm: Unplug drm device when unregistering it

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Message-ID: <20170426203609.2ezdzad54rgnotnr@art_vandelay>
Date:   Wed, 26 Apr 2017 16:36:09 -0400
From:   Sean Paul <seanpaul@...omium.org>
To:     Ville Syrjälä <ville.syrjala@...ux.intel.com>
Cc:     Jeffy Chen <jeffy.chen@...k-chips.com>,
        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 v8 1/2] drm: Unplug drm device when unregistering it

On Wed, Apr 26, 2017 at 10:43:31PM +0300, Ville Syrjälä wrote:
> On Wed, Apr 12, 2017 at 10:55:29AM +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.
> > 
> > Signed-off-by: Jeffy Chen <jeffy.chen@...k-chips.com>
> > Reviewed-by: Sean Paul <seanpaul@...omium.org>
> > 
> > ---
> > 
> > Changes in v8:
> > Fix hang when unregistering drm dev with open_count 0
> > 
> > Changes in v7:
> > Address Sean Paul <seanpaul@...omium.org>'s comments.
> > 
> > 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     | 19 +++----------------
> >  drivers/gpu/drm/udl/udl_drv.c |  2 +-
> >  include/drm/drmP.h            |  5 +++--
> >  include/drm/drm_drv.h         |  1 -
> >  4 files changed, 7 insertions(+), 20 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
> > index b5c6bb4..cc2d018 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
> > @@ -787,6 +771,8 @@ 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);
> 
> This makes me think this has something to do with actual plugs, be
> they the bath tub kind or some *ahem* other kind.
> 
> /methinks this should at least be called set_plugged_state or
> something like that. Or maybe there's an even better name that
> could be used?

thanks for reviewing this, Ville. fwiw, we decided this patch wasn't
worth carrying upstream (see my response to v11 in
<20170414151503.lmpp3udfuycavfki@..._vandelay>).

Sean

> 
> > +
> >  	ret = 0;
> >  
> >  	DRM_INFO("Initialized %s %d.%d.%d %s for %s on minor %d\n",
> > @@ -826,6 +812,7 @@ 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..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)
> >  {
> >  	smp_wmb();
> > -	atomic_set(&dev->unplugged, 1);
> > +	atomic_set(&dev->unplugged, !plugged);
> >  }
> >  
> >  static inline int drm_device_is_unplugged(struct drm_device *dev)
> > 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);
> >  
> > -- 
> > 2.1.4
> > 
> > 
> > _______________________________________________
> > dri-devel mailing list
> > dri-devel@...ts.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/dri-devel
> 
> -- 
> Ville Syrjälä
> Intel OTC

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

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