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-rw-r--r--include/uapi/linux/membarrier.h23
1 files changed, 16 insertions, 7 deletions
diff --git a/include/uapi/linux/membarrier.h b/include/uapi/linux/membarrier.h
index 6d47b3249d8a..4e01ad7ffe98 100644
--- a/include/uapi/linux/membarrier.h
+++ b/include/uapi/linux/membarrier.h
@@ -52,21 +52,30 @@
* (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 returns 0 on success. The
+ * "expedited" commands complete faster than
+ * the non-expedited ones, they never block,
+ * but have the downside of causing extra
+ * overhead. A process needs to register its
+ * intent to use the private expedited command
+ * prior to using it, otherwise this command
+ * returns -EPERM.
+ * @MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED:
+ * Register the process intent to use
+ * MEMBARRIER_CMD_PRIVATE_EXPEDITED. Always
+ * returns 0.
*
* 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),
+ MEMBARRIER_CMD_PRIVATE_EXPEDITED = (1 << 3),
+ MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED = (1 << 4),
};
#endif /* _UAPI_LINUX_MEMBARRIER_H */