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

[Daniel Vetter]

Legacy drivers insist that we really take all the locks in this path,
and the harm in doing so is minimal.

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>
---
 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..42257f373c59 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