Re: [PATCH 2/2] drm: make unplugged flag specific to udl driver

[Haixia Shi <hshi@xxxxxxxxxxxx>]

> +       if (udl_device_is_unplugged(dev) &&
> +               nr != DRM_IOCTL_NR(DRM_IOCTL_MODE_SETCRTC) &&
> +               nr != DRM_IOCTL_NR(DRM_IOCTL_MODE_RMFB) &&
> +               nr != DRM_IOCTL_NR(DRM_IOCTL_MODE_DESTROY_DUMB))
> +               return -ENODEV;
>
>Why?
>
>Just do:
>
>        if (udl_device_is_unplugged(dev))
>                return -ENODEV;
>
>Why this complex logic here?

Because there are legitimate ioctl calls after UDL is unplugged. See crbug.com/583508 and crbug.com/583758 for some background.

The userspace (Chrome in this case) has allocated FBs and Dumb buffers on the drm device and needs to be given a chance to properly deallocate them (via RMFB and DESTROY_DUMB). In addition, it needs to call SETCRTC with fb_id = 0 to properly release the last refcount on the primary fb.

I initially proposed adding an "UNPLUG_DISALLOW" flag to ioctls so that we can whitelist them on a case-by-case basis but that proposal got shot down as being unnecessary, but you can see my original patch at https://chromium-review.googlesource.com/#/c/326160/

On Wed, Feb 10, 2016 at 4:24 AM, David Herrmann <dh.herrmann@xxxxxxxxx> wrote:

Hi

On Tue, Feb 9, 2016 at 10:05 PM, Haixia Shi <hshi@xxxxxxxxxxxx> wrote:
> Remove the general drm_device_is_unplugged() checks, and move the unplugged
> flag handling logic into drm/udl. In general we want to keep driver-specific
> logic out of common drm code.
>
> Signed-off-by: Haixia Shi <hshi@xxxxxxxxxxxx>
> Reviewed-by: Stéphane Marchesin <marcheu@xxxxxxxxxxxx>
> ---
>  drivers/gpu/drm/drm_drv.c           |  6 ----
>  drivers/gpu/drm/drm_fops.c          |  2 --
>  drivers/gpu/drm/drm_gem.c           |  3 --
>  drivers/gpu/drm/drm_ioctl.c         |  3 --
>  drivers/gpu/drm/drm_vm.c            |  3 --
>  drivers/gpu/drm/udl/udl_connector.c |  2 +-
>  drivers/gpu/drm/udl/udl_drv.c       |  7 +++--
>  drivers/gpu/drm/udl/udl_drv.h       |  6 ++++
>  drivers/gpu/drm/udl/udl_fb.c        |  2 +-
>  drivers/gpu/drm/udl/udl_gem.c       |  5 +++
>  drivers/gpu/drm/udl/udl_main.c      | 61 +++++++++++++++++++++++++++++++++++++
>  include/drm/drmP.h                  | 14 ---------
>  12 files changed, 78 insertions(+), 36 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
> index 167c8d3..f93ee12 100644
> --- a/drivers/gpu/drm/drm_drv.c
> +++ b/drivers/gpu/drm/drm_drv.c
> @@ -376,9 +376,6 @@ struct drm_minor *drm_minor_acquire(unsigned int minor_id)
>
>         if (!minor) {
>                 return ERR_PTR(-ENODEV);
> -       } else if (drm_device_is_unplugged(minor->dev)) {
> -               drm_dev_unref(minor->dev);
> -               return ERR_PTR(-ENODEV);
>         }
>
>         return minor;
> @@ -464,9 +461,6 @@ void drm_unplug_dev(struct drm_device *dev)
>         drm_minor_unregister(dev, DRM_MINOR_CONTROL);
>
>         mutex_lock(&drm_global_mutex);
> -
> -       drm_device_set_unplugged(dev);
> -
>         if (dev->open_count == 0) {
>                 drm_put_dev(dev);
>         }
> diff --git a/drivers/gpu/drm/drm_fops.c b/drivers/gpu/drm/drm_fops.c
> index 1ea8790..b4332d4 100644
> --- a/drivers/gpu/drm/drm_fops.c
> +++ b/drivers/gpu/drm/drm_fops.c
> @@ -497,8 +497,6 @@ int drm_release(struct inode *inode, struct file *filp)
>
>         if (!--dev->open_count) {
>                 retcode = drm_lastclose(dev);
> -               if (drm_device_is_unplugged(dev))
> -                       drm_put_dev(dev);
>         }
>         mutex_unlock(&drm_global_mutex);
>
> diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
> index 2e8c77e..c622e32 100644
> --- a/drivers/gpu/drm/drm_gem.c
> +++ b/drivers/gpu/drm/drm_gem.c
> @@ -900,9 +900,6 @@ int drm_gem_mmap(struct file *filp, struct vm_area_struct *vma)
>         struct drm_vma_offset_node *node;
>         int ret;
>
> -       if (drm_device_is_unplugged(dev))
> -               return -ENODEV;
> -
>         drm_vma_offset_lock_lookup(dev->vma_offset_manager);
>         node = drm_vma_offset_exact_lookup_locked(dev->vma_offset_manager,
>                                                   vma->vm_pgoff,
> diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c
> index 8ce2a0c..f959074 100644
> --- a/drivers/gpu/drm/drm_ioctl.c
> +++ b/drivers/gpu/drm/drm_ioctl.c
> @@ -695,9 +695,6 @@ long drm_ioctl(struct file *filp,
>
>         dev = file_priv->minor->dev;
>
> -       if (drm_device_is_unplugged(dev))
> -               return -ENODEV;
> -
>         is_driver_ioctl = nr >= DRM_COMMAND_BASE && nr < DRM_COMMAND_END;
>
>         if (is_driver_ioctl) {
> diff --git a/drivers/gpu/drm/drm_vm.c b/drivers/gpu/drm/drm_vm.c
> index f90bd5f..3a68be4 100644
> --- a/drivers/gpu/drm/drm_vm.c
> +++ b/drivers/gpu/drm/drm_vm.c
> @@ -657,9 +657,6 @@ int drm_legacy_mmap(struct file *filp, struct vm_area_struct *vma)
>         struct drm_device *dev = priv->minor->dev;
>         int ret;
>
> -       if (drm_device_is_unplugged(dev))
> -               return -ENODEV;
> -
>         mutex_lock(&dev->struct_mutex);
>         ret = drm_mmap_locked(filp, vma);
>         mutex_unlock(&dev->struct_mutex);
> diff --git a/drivers/gpu/drm/udl/udl_connector.c b/drivers/gpu/drm/udl/udl_connector.c
> index 4709b54..b168f2c 100644
> --- a/drivers/gpu/drm/udl/udl_connector.c
> +++ b/drivers/gpu/drm/udl/udl_connector.c
> @@ -96,7 +96,7 @@ static int udl_mode_valid(struct drm_connector *connector,
>  static enum drm_connector_status
>  udl_detect(struct drm_connector *connector, bool force)
>  {
> -       if (drm_device_is_unplugged(connector->dev))
> +       if (udl_device_is_unplugged(connector->dev))
>                 return connector_status_disconnected;
>         return connector_status_connected;
>  }
> diff --git a/drivers/gpu/drm/udl/udl_drv.c b/drivers/gpu/drm/udl/udl_drv.c
> index d5728ec..f5c2a97 100644
> --- a/drivers/gpu/drm/udl/udl_drv.c
> +++ b/drivers/gpu/drm/udl/udl_drv.c
> @@ -24,12 +24,12 @@ static const struct vm_operations_struct udl_gem_vm_ops = {
>
>  static const struct file_operations udl_driver_fops = {
>         .owner = THIS_MODULE,
> -       .open = drm_open,
> +       .open = udl_drm_open,
>         .mmap = udl_drm_gem_mmap,
>         .poll = drm_poll,
>         .read = drm_read,
> -       .unlocked_ioctl = drm_ioctl,
> -       .release = drm_release,
> +       .unlocked_ioctl = udl_drm_ioctl,
> +       .release = udl_drm_release,
>  #ifdef CONFIG_COMPAT
>         .compat_ioctl = drm_compat_ioctl,
>  #endif
> @@ -97,6 +97,7 @@ static void udl_usb_disconnect(struct usb_interface *interface)
>         drm_connector_unplug_all(dev);
>         udl_fbdev_unplug(dev);
>         udl_drop_usb(dev);
> +       udl_device_set_unplugged(dev);
>         drm_unplug_dev(dev);
>  }
>
> diff --git a/drivers/gpu/drm/udl/udl_drv.h b/drivers/gpu/drm/udl/udl_drv.h
> index 4a064ef..75aa91c 100644
> --- a/drivers/gpu/drm/udl/udl_drv.h
> +++ b/drivers/gpu/drm/udl/udl_drv.h
> @@ -65,6 +65,7 @@ struct udl_device {
>         atomic_t bytes_identical; /* saved effort with backbuffer comparison */
>         atomic_t bytes_sent; /* to usb, after compression including overhead */
>         atomic_t cpu_kcycles_used; /* transpired during pixel processing */
> +       atomic_t unplugged; /* device has been unplugged or gone away */
>  };
>
>  struct udl_gem_object {
> @@ -133,6 +134,9 @@ int udl_gem_get_pages(struct udl_gem_object *obj);
>  void udl_gem_put_pages(struct udl_gem_object *obj);
>  int udl_gem_vmap(struct udl_gem_object *obj);
>  void udl_gem_vunmap(struct udl_gem_object *obj);
> +int udl_drm_open(struct inode *inode, struct file *filp);
> +int udl_drm_release(struct inode *inode, struct file *filp);
> +int udl_drm_ioctl(struct file *filp, unsigned int cmd, unsigned long arg);
>  int udl_drm_gem_mmap(struct file *filp, struct vm_area_struct *vma);
>  int udl_gem_fault(struct vm_area_struct *vma, struct vm_fault *vmf);
>
> @@ -140,6 +144,8 @@ int udl_handle_damage(struct udl_framebuffer *fb, int x, int y,
>                       int width, int height);
>
>  int udl_drop_usb(struct drm_device *dev);
> +void udl_device_set_unplugged(struct drm_device *dev);
> +int udl_device_is_unplugged(struct drm_device *dev);
>
>  #define CMD_WRITE_RAW8   "\xAF\x60" /**< 8 bit raw write command. */
>  #define CMD_WRITE_RL8    "\xAF\x61" /**< 8 bit run length command. */
> diff --git a/drivers/gpu/drm/udl/udl_fb.c b/drivers/gpu/drm/udl/udl_fb.c
> index 200419d..df1d53e 100644
> --- a/drivers/gpu/drm/udl/udl_fb.c
> +++ b/drivers/gpu/drm/udl/udl_fb.c
> @@ -325,7 +325,7 @@ static int udl_fb_open(struct fb_info *info, int user)
>         struct udl_device *udl = dev->dev_private;
>
>         /* If the USB device is gone, we don't accept new opens */
> -       if (drm_device_is_unplugged(udl->ddev))
> +       if (udl_device_is_unplugged(udl->ddev))
>                 return -ENODEV;
>
>         ufbdev->fb_count++;
> diff --git a/drivers/gpu/drm/udl/udl_gem.c b/drivers/gpu/drm/udl/udl_gem.c
> index 2a0a784..33c302f 100644
> --- a/drivers/gpu/drm/udl/udl_gem.c
> +++ b/drivers/gpu/drm/udl/udl_gem.c
> @@ -86,8 +86,13 @@ int udl_dumb_create(struct drm_file *file,
>
>  int udl_drm_gem_mmap(struct file *filp, struct vm_area_struct *vma)
>  {
> +       struct drm_file *priv = filp->private_data;
> +       struct drm_device *dev = priv->minor->dev;
>         int ret;
>
> +       if (udl_device_is_unplugged(dev))
> +               return -ENODEV;
> +
>         ret = drm_gem_mmap(filp, vma);
>         if (ret)
>                 return ret;
> diff --git a/drivers/gpu/drm/udl/udl_main.c b/drivers/gpu/drm/udl/udl_main.c
> index 33dbfb2..2ba3ee3 100644
> --- a/drivers/gpu/drm/udl/udl_main.c
> +++ b/drivers/gpu/drm/udl/udl_main.c
> @@ -350,3 +350,64 @@ int udl_driver_unload(struct drm_device *dev)
>         kfree(udl);
>         return 0;
>  }
> +
> +int udl_drm_open(struct inode *inode, struct file *filp)
> +{
> +       struct drm_file *file_priv;
> +       struct drm_minor *minor;
> +
> +       int ret = drm_open(inode, filp);
> +       if (ret)
> +               return ret;
> +
> +       file_priv = filp->private_data;
> +       minor = file_priv->minor;
> +       if (udl_device_is_unplugged(minor->dev)) {
> +               drm_dev_unref(minor->dev);
> +               return -ENODEV;
> +       }

This doesn't make sense to me. You're called here with global-mutex
held, so you can just check udl_device_is_unplugged() before calling
into drm_open().

> +
> +       return 0;
> +}
> +
> +int udl_drm_release(struct inode *inode, struct file *filp)
> +{
> +       struct drm_file *file_priv = filp->private_data;
> +       struct drm_device *dev = file_priv->minor->dev;
> +
> +       int ret = drm_release(inode, filp);
> +       if (!dev->open_count && udl_device_is_unplugged(dev))
> +               drm_put_dev(dev);

This should rather be:

        drm_release(inode, filp);
        mutex_lock(&drm_global_mutex);
        if (!dev->open_count && udl_device_is_unplugged(dev))
                drm_put_dev(dev);
        mutex_unlock(&drm_global_mutex);

        return 0;

There is no reason to look at the return code of drm_release(), ever.

> +
> +       return ret;
> +}
> +
> +int udl_drm_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
> +{
> +       struct drm_file *file_priv = filp->private_data;
> +       struct drm_device *dev = file_priv->minor->dev;
> +       unsigned int nr = DRM_IOCTL_NR(cmd);
> +
> +       if (udl_device_is_unplugged(dev) &&
> +               nr != DRM_IOCTL_NR(DRM_IOCTL_MODE_SETCRTC) &&
> +               nr != DRM_IOCTL_NR(DRM_IOCTL_MODE_RMFB) &&
> +               nr != DRM_IOCTL_NR(DRM_IOCTL_MODE_DESTROY_DUMB))
> +               return -ENODEV;

Why?

Just do:

        if (udl_device_is_unplugged(dev))
                return -ENODEV;

Why this complex logic here?

Thanks
David

> +
> +       return drm_ioctl(filp, cmd, arg);
> +}
> +
> +void udl_device_set_unplugged(struct drm_device *dev)
> +{
> +       struct udl_device *udl = dev->dev_private;
> +       smp_wmb();
> +       atomic_set(&udl->unplugged, 1);
> +}
> +
> +int udl_device_is_unplugged(struct drm_device *dev)
> +{
> +       struct udl_device *udl = dev->dev_private;
> +       int ret = atomic_read(&udl->unplugged);
> +       smp_rmb();
> +       return ret;
> +}
> diff --git a/include/drm/drmP.h b/include/drm/drmP.h
> index d7162cf..40c6099 100644
> --- a/include/drm/drmP.h
> +++ b/include/drm/drmP.h
> @@ -748,7 +748,6 @@ struct drm_device {
>         struct drm_minor *control;              /**< Control node */
>         struct drm_minor *primary;              /**< Primary node */
>         struct drm_minor *render;               /**< Render node */
> -       atomic_t unplugged;                     /**< Flag whether dev is dead */
>         struct inode *anon_inode;               /**< inode for private address-space */
>         char *unique;                           /**< unique name of the device */
>         /*@} */
> @@ -879,19 +878,6 @@ 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);
> -       smp_rmb();
> -       return ret;
> -}
> -
>  static inline bool drm_is_render_client(const struct drm_file *file_priv)
>  {
>         return file_priv->minor->type == DRM_MINOR_RENDER;
> --
> 2.7.0.rc3.207.g0ac5344
>

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