[PATCH 11/14] drm: Remove locking for legacy ioctls and DRM_UNLOCKED

[Alex Deucher]

On Wed, Nov 22, 2023 at 7:25 AM Thomas Zimmermann <tzimmermann at suse.de> wrote:
>
> Modern DRM drivers acquire ioctl locks by themselves. Legacy ioctls
> for user-space mode setting used to acquire drm_global_mutex. After
> removing the ioctl entry points, also remove the locking code. The only
> legacy ioctl without global locking was VBLANK_WAIT, which has been
> removed as well. Hence remove the related DRM_UNLOCKED flag.
>
> Signed-off-by: Thomas Zimmermann <tzimmermann at suse.de>

Acked-by: Alex Deucher <alexander.deucher at amd.com>

> ---
>  drivers/gpu/drm/drm_ioc32.c |  2 +-
>  drivers/gpu/drm/drm_ioctl.c | 23 +++++++----------------
>  include/drm/drm_ioctl.h     | 11 -----------
>  3 files changed, 8 insertions(+), 28 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_ioc32.c b/drivers/gpu/drm/drm_ioc32.c
> index 910cadf14756e..129e2b91dbfe7 100644
> --- a/drivers/gpu/drm/drm_ioc32.c
> +++ b/drivers/gpu/drm/drm_ioc32.c
> @@ -273,7 +273,7 @@ static int compat_drm_wait_vblank(struct file *file, unsigned int cmd,
>         req.request.type = req32.request.type;
>         req.request.sequence = req32.request.sequence;
>         req.request.signal = req32.request.signal;
> -       err = drm_ioctl_kernel(file, drm_wait_vblank_ioctl, &req, DRM_UNLOCKED);
> +       err = drm_ioctl_kernel(file, drm_wait_vblank_ioctl, &req, 0);
>
>         req32.reply.type = req.reply.type;
>         req32.reply.sequence = req.reply.sequence;
> diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c
> index 9c6326b908e74..1cf1de342d6aa 100644
> --- a/drivers/gpu/drm/drm_ioctl.c
> +++ b/drivers/gpu/drm/drm_ioctl.c
> @@ -583,7 +583,7 @@ static const struct drm_ioctl_desc drm_ioctls[] = {
>
>         DRM_IOCTL_DEF(DRM_IOCTL_FINISH, drm_noop, DRM_AUTH),
>
> -       DRM_IOCTL_DEF(DRM_IOCTL_WAIT_VBLANK, drm_wait_vblank_ioctl, DRM_UNLOCKED),
> +       DRM_IOCTL_DEF(DRM_IOCTL_WAIT_VBLANK, drm_wait_vblank_ioctl, 0),
>
>         DRM_IOCTL_DEF(DRM_IOCTL_UPDATE_DRAW, drm_noop, DRM_AUTH|DRM_MASTER|DRM_ROOT_ONLY),
>
> @@ -716,7 +716,7 @@ long drm_ioctl_kernel(struct file *file, drm_ioctl_t *func, void *kdata,
>  {
>         struct drm_file *file_priv = file->private_data;
>         struct drm_device *dev = file_priv->minor->dev;
> -       int retcode;
> +       int ret;
>
>         /* Update drm_file owner if fd was passed along. */
>         drm_file_update_pid(file_priv);
> @@ -724,20 +724,11 @@ long drm_ioctl_kernel(struct file *file, drm_ioctl_t *func, void *kdata,
>         if (drm_dev_is_unplugged(dev))
>                 return -ENODEV;
>
> -       retcode = drm_ioctl_permit(flags, file_priv);
> -       if (unlikely(retcode))
> -               return retcode;
> -
> -       /* Enforce sane locking for modern driver ioctls. */
> -       if (likely(!drm_core_check_feature(dev, DRIVER_LEGACY)) ||
> -           (flags & DRM_UNLOCKED))
> -               retcode = func(dev, kdata, file_priv);
> -       else {
> -               mutex_lock(&drm_global_mutex);
> -               retcode = func(dev, kdata, file_priv);
> -               mutex_unlock(&drm_global_mutex);
> -       }
> -       return retcode;
> +       ret = drm_ioctl_permit(flags, file_priv);
> +       if (unlikely(ret))
> +               return ret;
> +
> +       return func(dev, kdata, file_priv);
>  }
>  EXPORT_SYMBOL(drm_ioctl_kernel);
>
> diff --git a/include/drm/drm_ioctl.h b/include/drm/drm_ioctl.h
> index 6ed61c371f6ce..171760b6c4a14 100644
> --- a/include/drm/drm_ioctl.h
> +++ b/include/drm/drm_ioctl.h
> @@ -109,17 +109,6 @@ enum drm_ioctl_flags {
>          * This is equivalent to callers with the SYSADMIN capability.
>          */
>         DRM_ROOT_ONLY           = BIT(2),
> -       /**
> -        * @DRM_UNLOCKED:
> -        *
> -        * Whether &drm_ioctl_desc.func should be called with the DRM BKL held
> -        * or not. Enforced as the default for all modern drivers, hence there
> -        * should never be a need to set this flag.
> -        *
> -        * Do not use anywhere else than for the VBLANK_WAIT IOCTL, which is the
> -        * only legacy IOCTL which needs this.
> -        */
> -       DRM_UNLOCKED            = BIT(4),
>         /**
>          * @DRM_RENDER_ALLOW:
>          *
> --
> 2.42.1
>