1 files changed, 21 insertions, 2 deletions

diff --git a/include/uapi/linux/membarrier.h b/include/uapi/linux/membarrier.h
index e0b108bd2624..6d47b3249d8a 100644
--- a/include/uapi/linux/membarrier.h
+++ b/include/uapi/linux/membarrier.h
@@ -40,14 +40,33 @@
  *                          (non-running threads are de facto in such a
  *                          state). This covers threads from all processes
  *                          running on the system. This command returns 0.
+ * @MEMBARRIER_CMD_PRIVATE_EXPEDITED:
+ *                          Execute a memory barrier on each running
+ *                          thread belonging to the same process as the current
+ *                          thread. Upon return from system call, the
+ *                          caller thread is ensured that all its running
+ *                          threads siblings have passed through a state
+ *                          where all memory accesses to user-space
+ *                          addresses match program order between entry
+ *                          to and return from the system call
+ *                          (non-running threads are de facto in such a
+ *                          state). This only covers threads from the
+ *                          same processes as the caller thread. This
+ *                          command returns 0. The "expedited" commands
+ *                          complete faster than the non-expedited ones,
+ *                          they never block, but have the downside of
+ *                          causing extra overhead.
  *
  * Command to be passed to the membarrier system call. The commands need to
  * be a single bit each, except for MEMBARRIER_CMD_QUERY which is assigned to
  * the value 0.
  */
 enum membarrier_cmd {
-        MEMBARRIER_CMD_QUERY = 0,
-        MEMBARRIER_CMD_SHARED = (1 << 0),
+        MEMBARRIER_CMD_QUERY                    = 0,
+        MEMBARRIER_CMD_SHARED                   = (1 << 0),
+        /* reserved for MEMBARRIER_CMD_SHARED_EXPEDITED (1 << 1) */
+        /* reserved for MEMBARRIER_CMD_PRIVATE (1 << 2) */
+        MEMBARRIER_CMD_PRIVATE_EXPEDITED        = (1 << 3),
 };
 
 #endif /* _UAPI_LINUX_MEMBARRIER_H */