Patch "drm: Wrap direct calls to driver->gem_free_object from CMA" has been added to the 4.6-stable tree

This is a note to let you know that I've just added the patch titled

    drm: Wrap direct calls to driver->gem_free_object from CMA

to the 4.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
drm-wrap-direct-calls-to-driver-gem_free_object-from-cma.patch
and it can be found in the queue-4.6 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Chris Wilson <[email protected]>
Date: Tue, 31 May 2016 22:25:52 +0100
Subject: drm: Wrap direct calls to driver->gem_free_object from CMA

From: Chris Wilson <[email protected]>

commit afe705be38f1e65b173868486944377186b9f206 upstream.

Since the introduction of (struct_mutex) lockless GEM bo freeing, there are a pair of driver vfuncs for freeing the GEM bo, of which the driver may choose to only implement driver->gem_object_free_unlocked (and so avoid taking the struct_mutex along the free path). However, the CMA GEM helpers were still calling driver->gem_free_object directly, now NULL, and promptly dying on the fancy new lockless drivers. Oops.

Robert Foss bisected this to b82caafcf2303 (drm/vc4: Use lockless gem BO free callback) on his vc4 device, but that just serves as an enabler for 9f0ba539d13ae (drm/gem: support BO freeing without dev->struct_mutex).

---
 drivers/gpu/drm/drm_fb_cma_helper.c  |    2 +-
 drivers/gpu/drm/drm_gem_cma_helper.c |   12 +++---------
 2 files changed, 4 insertions(+), 10 deletions(-)

@@ -301,7 +301,7 @@ static int drm_fbdev_cma_create(struct d
 err_fb_info_destroy:
 	drm_fb_helper_release_fbi(helper);
 err_gem_free_object:
-	dev->driver->gem_free_object(&obj->base);
+	drm_gem_object_unreference_unlocked(&obj->base);
 	return ret;
 }
 

@@ -121,7 +121,7 @@ struct drm_gem_cma_object *drm_gem_cma_c
 	return cma_obj;
 
 error:
-	drm->driver->gem_free_object(&cma_obj->base);
+	drm_gem_object_unreference_unlocked(&cma_obj->base);
 	return ERR_PTR(ret);
 }
 EXPORT_SYMBOL_GPL(drm_gem_cma_create);

@@ -162,18 +162,12 @@ drm_gem_cma_create_with_handle(struct dr
 	 * and handle has the id what user can see.
 	 */
 	ret = drm_gem_handle_create(file_priv, gem_obj, handle);
-	if (ret)
-		goto err_handle_create;
-
 	/* drop reference from allocate - handle holds it now. */
 	drm_gem_object_unreference_unlocked(gem_obj);
+	if (ret)
+		return ERR_PTR(ret);
 
 	return cma_obj;
-
-err_handle_create:
-	drm->driver->gem_free_object(gem_obj);
-
-	return ERR_PTR(ret);
 }
 
 /**

Patches currently in stable-queue which might be from [email protected] are

queue-4.6/sched-fair-fix-cfs_rq-avg-tracking-underflow.patch queue-4.6/drm-i915-update-ifdeffery-for-mutex-owner.patch queue-4.6/drm-wrap-direct-calls-to-driver-gem_free_object-from-cma.patch queue-4.6/locking-ww_mutex-report-recursive-ww_mutex-locking-early.patch