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

[jeffy]

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@xxxxxxxxxxxxxx>
> > > Reviewed-by: Sean Paul <seanpaul@xxxxxxxxxxxx>
> > >
> > > ---
> > >
> > > Changes in v7:
> > > Address Sean Paul <seanpaul@xxxxxxxxxxxx>'s comments.
> > >
> > > Changes in v6:
> > > Address Daniel Vetter <daniel@xxxxxxxx>'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
> > >
> > >
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