dma-buf/fence: add fence_is_later()

Return true when fence 1 is later than fence 2 without
checking if any of them are signaled.

Useful for driver specific resource handling based on fences.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>

diff --git a/include/linux/fence.h b/include/linux/fence.h
index a4084d6bb851c7f86ba8b3b777c484b60ff399de..bb522011383bca52ba248110a2a4c1e86d1f5aa3 100644 (file)
--- a/include/linux/fence.h
+++ b/include/linux/fence.h
@@ -279,6 +279,22 @@ fence_is_signaled(struct fence *fence)
        return false;
 }
 
+/**
+ * fence_is_later - return if f1 is chronologically later than f2
+ * @f1:        [in]    the first fence from the same context
+ * @f2:        [in]    the second fence from the same context
+ *
+ * Returns true if f1 is chronologically later than f2. Both fences must be
+ * from the same context, since a seqno is not re-used across contexts.
+ */
+static inline bool fence_is_later(struct fence *f1, struct fence *f2)
+{
+       if (WARN_ON(f1->context != f2->context))
+               return false;
+
+       return f1->seqno - f2->seqno < INT_MAX;
+}
+
 /**
  * fence_later - return the chronologically later fence
  * @f1:        [in]    the first fence from the same context
@@ -298,10 +314,10 @@ static inline struct fence *fence_later(struct fence *f1, struct fence *f2)
         * set if enable_signaling wasn't called, and enabling that here is
         * overkill.
         */
-       if (f2->seqno - f1->seqno <= INT_MAX)
-               return fence_is_signaled(f2) ? NULL : f2;
-       else
+       if (fence_is_later(f1, f2))
                return fence_is_signaled(f1) ? NULL : f1;
+       else
+               return fence_is_signaled(f2) ? NULL : f2;
 }
 
 signed long fence_wait_timeout(struct fence *, bool intr, signed long timeout);