drm/omap: gem: Fix mm_list locking

- None of the list walkings where protected.

- Switch to a mutex since the list walking at device resume time can
  sleep when pinning buffers through the tiler.

Only thing we need to be careful with here is that while we walk the
list we can't unreference any gem objects, since the final unref would
result in a recursive deadlock. But the only functions that walk the
list is the device resume and debugfs dumping, so all safe.

Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>

1 files changed, 9 insertions, 6 deletions

diff --git a/drivers/gpu/drm/omapdrm/omap_gem.c b/drivers/gpu/drm/omapdrm/omap_gem.c
index cebbdf081e5d..4ba5d035c590 100644
--- a/drivers/gpu/drm/omapdrm/omap_gem.c
+++ b/drivers/gpu/drm/omapdrm/omap_gem.c
@@ -1000,6 +1000,7 @@ int omap_gem_resume(struct drm_device *dev)
 	struct omap_gem_object *omap_obj;
 	int ret = 0;
 
+	mutex_lock(&priv->list_lock);
 	list_for_each_entry(omap_obj, &priv->obj_list, mm_list) {
 		if (omap_obj->block) {
 			struct drm_gem_object *obj = &omap_obj->base;
@@ -1011,12 +1012,14 @@ int omap_gem_resume(struct drm_device *dev)
 					omap_obj->roll, true);
 			if (ret) {
 				dev_err(dev->dev, "could not repin: %d\n", ret);
-				return ret;
+				goto done;
 			}
 		}
 	}
 
-	return 0;
+done:
+	mutex_unlock(&priv->list_lock);
+	return ret;
 }
 #endif
 
@@ -1086,9 +1089,9 @@ void omap_gem_free_object(struct drm_gem_object *obj)
 
 	omap_gem_evict(obj);
 
-	spin_lock(&priv->list_lock);
+	mutex_lock(&priv->list_lock);
 	list_del(&omap_obj->mm_list);
-	spin_unlock(&priv->list_lock);
+	mutex_unlock(&priv->list_lock);
 
 	/*
 	 * We own the sole reference to the object at this point, but to keep
@@ -1218,9 +1221,9 @@ struct drm_gem_object *omap_gem_new(struct drm_device *dev,
 			goto err_release;
 	}
 
-	spin_lock(&priv->list_lock);
+	mutex_lock(&priv->list_lock);
 	list_add(&omap_obj->mm_list, &priv->obj_list);
-	spin_unlock(&priv->list_lock);
+	mutex_unlock(&priv->list_lock);
 
 	return obj;