[PATCH] drm: Take mode_config.mutex in setcrtc ioctl

[Alex Deucher]

On Thu, Apr 6, 2017 at 3:06 PM, Daniel Vetter <daniel.vetter at ffwll.ch> wrote:
> Legacy drivers insist that we really take all the locks in this path,
> and the harm in doing so is minimal.
>
> v2: Like git add, it exists :(
>
> Fixes: 2ceb585a956c ("drm: Add explicit acquire ctx handling around ->set_config")
> Cc: Harry Wentland <harry.wentland at amd.com>
> Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
> Cc: Daniel Vetter <daniel.vetter at intel.com>
> Cc: Jani Nikula <jani.nikula at linux.intel.com>
> Cc: Sean Paul <seanpaul at chromium.org>
> Cc: David Airlie <airlied at linux.ie>
> Cc: dri-devel at lists.freedesktop.org
> Cc: Alex Deucher <alexdeucher at gmail.com>
> Reported-by: Alex Deucher <alexdeucher at gmail.com>
> Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>

This actually matches what I tested locally.

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

> ---
>  drivers/gpu/drm/drm_crtc.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
> index d69e180fc563..5af25ce5bf7c 100644
> --- a/drivers/gpu/drm/drm_crtc.c
> +++ b/drivers/gpu/drm/drm_crtc.c
> @@ -576,6 +576,7 @@ int drm_mode_setcrtc(struct drm_device *dev, void *data,
>         }
>         DRM_DEBUG_KMS("[CRTC:%d:%s]\n", crtc->base.id, crtc->name);
>
> +       mutex_lock(&crtc->dev->mode_config.mutex);
>         drm_modeset_acquire_init(&ctx, 0);
>  retry:
>         ret = drm_modeset_lock_all_ctx(crtc->dev, &ctx);
> @@ -721,6 +722,7 @@ int drm_mode_setcrtc(struct drm_device *dev, void *data,
>         }
>         drm_modeset_drop_locks(&ctx);
>         drm_modeset_acquire_fini(&ctx);
> +       mutex_unlock(&crtc->dev->mode_config.mutex);
>
>         return ret;
>  }
> --
> 2.11.0
>