@@ -92,16 +92,29 @@ struct srcu_struct {
struct lockdep_map dep_map;
};
-/* Values for size state variable (->srcu_size_state). */
-#define SRCU_SIZE_SMALL 0
-#define SRCU_SIZE_ALLOC 1
-#define SRCU_SIZE_WAIT_BARRIER 2
-#define SRCU_SIZE_WAIT_CALL 3
-#define SRCU_SIZE_WAIT_CBS1 4
-#define SRCU_SIZE_WAIT_CBS2 5
-#define SRCU_SIZE_WAIT_CBS3 6
-#define SRCU_SIZE_WAIT_CBS4 7
-#define SRCU_SIZE_BIG 8
+// Values for size state variable (->srcu_size_state). Once the state
+// has been set to SRCU_SIZE_ALLOC, the grace-period code advances through
+// this state machine one step per grace period until the SRCU_SIZE_BIG state
+// is reached. Otherwise, the state machine remains in the SRCU_SIZE_SMALL
+// state indefinitely.
+#define SRCU_SIZE_SMALL 0 // No srcu_node combining tree, ->node == NULL
+#define SRCU_SIZE_ALLOC 1 // An srcu_node tree is being allocated, initialized,
+ // and then referenced by ->node. It will not be used.
+#define SRCU_SIZE_WAIT_BARRIER 2 // The srcu_node tree starts being used by everything
+ // except call_srcu(), especially by srcu_barrier().
+ // By the end of this state, all CPUs and threads
+ // are aware of this tree's existence.
+#define SRCU_SIZE_WAIT_CALL 3 // The srcu_node tree starts being used by call_srcu().
+ // By the end of this state, all of the call_srcu()
+ // invocations that were running on a non-boot CPU
+ // and using the boot CPU's callback queue will have
+ // completed.
+#define SRCU_SIZE_WAIT_CBS1 4 // Don't trust the ->srcu_have_cbs[] grace-period
+#define SRCU_SIZE_WAIT_CBS2 5 // sequence elements or the ->srcu_data_have_cbs[]
+#define SRCU_SIZE_WAIT_CBS3 6 // CPU-bitmask elements until all four elements of
+#define SRCU_SIZE_WAIT_CBS4 7 // each array have been initialized.
+#define SRCU_SIZE_BIG 8 // The srcu_node combining tree is fully initialized
+ // and all aspects of it are being put to use.
/* Values for state variable (bottom bits of ->srcu_gp_seq). */
#define SRCU_STATE_IDLE 0