Nouveau - Jul 2013 - [PATCH 10/11] drm/nvc0/fb: Take lock in nvc0_ram_put()

Kernel panic caused by list corruption in ltcg seems to indicate a concurrency
issue. Take mutex of pfb like nv50_ram_put() to eliminate concurrency.

Signed-off-by: Roy Spliet <r.spliet at student.tudelft.nl>
---
 drivers/gpu/drm/nouveau/core/subdev/fb/ramnvc0.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/core/subdev/fb/ramnvc0.c
b/drivers/gpu/drm/nouveau/core/subdev/fb/ramnvc0.c
index 9c3634a..abe0b61 100644
--- a/drivers/gpu/drm/nouveau/core/subdev/fb/ramnvc0.c
+++ b/drivers/gpu/drm/nouveau/core/subdev/fb/ramnvc0.c
@@ -33,11 +33,18 @@ void
 nvc0_ram_put(struct nouveau_fb *pfb, struct nouveau_mem **pmem)
 {
 	struct nouveau_ltcg *ltcg = nouveau_ltcg(pfb);
+	struct nouveau_mem *mem = *pmem;
 
-	if ((*pmem)->tag)
-		ltcg->tags_free(ltcg, &(*pmem)->tag);
+	*pmem = NULL;
+	if(unlikely(mem == NULL))
+		return;
 
-	nv50_ram_put(pfb, pmem);
+	mutex_lock(&pfb->base.mutex);
+	if (mem->tag)
+		ltcg->tags_free(ltcg, &mem->tag);
+	mutex_unlock(&pfb->base.mutex);
+
+	nv50_ram_put(pfb, &mem);
 }
 
 int
-- 
1.8.3.1