Merge branch 'drm-ttm-next' into drm-core-next

* drm-ttm-next:
  drm/radeon: Use the ttm execbuf utilities
  drm/ttm: Fix up io_mem_reserve / io_mem_free calling
  drm/ttm/vmwgfx: Have TTM manage the validation sequence.
  drm/ttm: Improved fencing of buffer object lists
  drm/ttm/radeon/nouveau: Kill the bo lock in favour of a bo device fence_lock
  drm/ttm: Don't deadlock on recursive multi-bo reservations
  drm/ttm: Optimize ttm_eu_backoff_reservation
  drm/ttm: Use kref_sub instead of repeatedly calling kref_put
  kref: Add a kref_sub function
  drm/ttm: Add a bo list reserve fastpath (v2)

1 files changed, 30 insertions, 0 deletions

diff --git a/lib/kref.c b/lib/kref.c
index d3d227a08a4..3efb882b11d 100644
--- a/lib/kref.c
+++ b/lib/kref.c
@@ -62,6 +62,36 @@ int kref_put(struct kref *kref, void (*release)(struct kref *kref))
 	return 0;
 }
 
+
+/**
+ * kref_sub - subtract a number of refcounts for object.
+ * @kref: object.
+ * @count: Number of recounts to subtract.
+ * @release: pointer to the function that will clean up the object when the
+ *	     last reference to the object is released.
+ *	     This pointer is required, and it is not acceptable to pass kfree
+ *	     in as this function.
+ *
+ * Subtract @count from the refcount, and if 0, call release().
+ * Return 1 if the object was removed, otherwise return 0.  Beware, if this
+ * function returns 0, you still can not count on the kref from remaining in
+ * memory.  Only use the return value if you want to see if the kref is now
+ * gone, not present.
+ */
+int kref_sub(struct kref *kref, unsigned int count,
+	     void (*release)(struct kref *kref))
+{
+	WARN_ON(release == NULL);
+	WARN_ON(release == (void (*)(struct kref *))kfree);
+
+	if (atomic_sub_and_test((int) count, &kref->refcount)) {
+		release(kref);
+		return 1;
+	}
+	return 0;
+}
+
 EXPORT_SYMBOL(kref_init);
 EXPORT_SYMBOL(kref_get);
 EXPORT_SYMBOL(kref_put);
+EXPORT_SYMBOL(kref_sub);