On Mon, May 29, 2017 at 5:25 PM, Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> 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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