[PATCH 4.9 038/116] drm/nouveau/ltc: protect clearing of comptags with mutex

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ben Skeggs <bskeggs@xxxxxxxxxx>

commit f4e65efc88b64c1dbca275d42a188edccedb56c6 upstream.

Signed-off-by: Ben Skeggs <bskeggs@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/gpu/drm/nouveau/nvkm/subdev/ltc/base.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/gpu/drm/nouveau/nvkm/subdev/ltc/base.c
+++ b/drivers/gpu/drm/nouveau/nvkm/subdev/ltc/base.c
@@ -47,8 +47,10 @@ nvkm_ltc_tags_clear(struct nvkm_ltc *ltc
 
 	BUG_ON((first > limit) || (limit >= ltc->num_tags));
 
+	mutex_lock(&ltc->subdev.mutex);
 	ltc->func->cbc_clear(ltc, first, limit);
 	ltc->func->cbc_wait(ltc);
+	mutex_unlock(&ltc->subdev.mutex);
 }
 
 int