rcu: Move gp_state_names[] and gp_state_getname() to tree_stall.h

Only tree_stall.h needs to get name from GP state, so this commit
moves the gp_state_names[] array and the gp_state_getname()
from kernel/rcu/tree.h and kernel/rcu/tree.c, respectively, to
kernel/rcu/tree_stall.h.  While moving gp_state_names[], this commit
uses the GCC syntax to ensure that the right string is associated with
the right CPP macro.
Signed-off-by: Lai Jiangshan <jiangshanlai@gmail.com>
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

kernel/rcu/tree.c

@@ -528,16 +528,6 @@ static struct rcu_node *rcu_get_root(void)
 	return &rcu_state.node[0];
 }
 
-/*
- * Convert a ->gp_state value to a character string.
- */
-static const char *gp_state_getname(short gs)
-{
-	if (gs < 0 || gs >= ARRAY_SIZE(gp_state_names))
-		return "???";
-	return gp_state_names[gs];
-}
-
 /*
  * Send along grace-period-related data for rcutorture diagnostics.
  */

kernel/rcu/tree.h

@@ -368,18 +368,6 @@ struct rcu_state {
 #define RCU_GP_CLEANUP   7	/* Grace-period cleanup started. */
 #define RCU_GP_CLEANED   8	/* Grace-period cleanup complete. */
 
-static const char * const gp_state_names[] = {
-	"RCU_GP_IDLE",
-	"RCU_GP_WAIT_GPS",
-	"RCU_GP_DONE_GPS",
-	"RCU_GP_ONOFF",
-	"RCU_GP_INIT",
-	"RCU_GP_WAIT_FQS",
-	"RCU_GP_DOING_FQS",
-	"RCU_GP_CLEANUP",
-	"RCU_GP_CLEANED",
-};
-
 /*
  * In order to export the rcu_state name to the tracing tools, it
  * needs to be added in the __tracepoint_string section.

kernel/rcu/tree_stall.h

@@ -279,6 +279,28 @@ static void print_cpu_stall_fast_no_hz(char *cp, int cpu)
 
 #endif /* #else #ifdef CONFIG_RCU_FAST_NO_HZ */
 
+static const char * const gp_state_names[] = {
+	[RCU_GP_IDLE] = "RCU_GP_IDLE",
+	[RCU_GP_WAIT_GPS] = "RCU_GP_WAIT_GPS",
+	[RCU_GP_DONE_GPS] = "RCU_GP_DONE_GPS",
+	[RCU_GP_ONOFF] = "RCU_GP_ONOFF",
+	[RCU_GP_INIT] = "RCU_GP_INIT",
+	[RCU_GP_WAIT_FQS] = "RCU_GP_WAIT_FQS",
+	[RCU_GP_DOING_FQS] = "RCU_GP_DOING_FQS",
+	[RCU_GP_CLEANUP] = "RCU_GP_CLEANUP",
+	[RCU_GP_CLEANED] = "RCU_GP_CLEANED",
+};
+
+/*
+ * Convert a ->gp_state value to a character string.
+ */
+static const char *gp_state_getname(short gs)
+{
+	if (gs < 0 || gs >= ARRAY_SIZE(gp_state_names))
+		return "???";
+	return gp_state_names[gs];
+}
+
 /*
  * Print out diagnostic information for the specified stalled CPU.
  *