rcu: Move rcu_nmi_{enter,exit}() to prepare for consolidation

This is a code-motion-only commit that prepares to define rcu_irq_enter()
in terms of rcu_nmi_enter() and rcu_irq_exit() in terms of rcu_irq_exit().
Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com>

kernel/rcu/tree.c

@@ -866,6 +866,44 @@ void rcu_user_enter(void)
 }
 #endif /* CONFIG_NO_HZ_FULL */
 
+/**
+ * rcu_nmi_exit - inform RCU of exit from NMI context
+ *
+ * If we are returning from the outermost NMI handler that interrupted an
+ * RCU-idle period, update rdtp->dynticks and rdtp->dynticks_nmi_nesting
+ * to let the RCU grace-period handling know that the CPU is back to
+ * being RCU-idle.
+ *
+ * If you add or remove a call to rcu_nmi_exit(), be sure to test
+ * with CONFIG_RCU_EQS_DEBUG=y.
+ */
+void rcu_nmi_exit(void)
+{
+	struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);
+
+	/*
+	 * Check for ->dynticks_nmi_nesting underflow and bad ->dynticks.
+	 * (We are exiting an NMI handler, so RCU better be paying attention
+	 * to us!)
+	 */
+	WARN_ON_ONCE(rdtp->dynticks_nmi_nesting <= 0);
+	WARN_ON_ONCE(rcu_dynticks_curr_cpu_in_eqs());
+
+	/*
+	 * If the nesting level is not 1, the CPU wasn't RCU-idle, so
+	 * leave it in non-RCU-idle state.
+	 */
+	if (rdtp->dynticks_nmi_nesting != 1) {
+		WRITE_ONCE(rdtp->dynticks_nmi_nesting, /* No store tearing. */
+			   rdtp->dynticks_nmi_nesting - 2);
+		return;
+	}
+
+	/* This NMI interrupted an RCU-idle CPU, restore RCU-idleness. */
+	WRITE_ONCE(rdtp->dynticks_nmi_nesting, 0); /* Avoid store tearing. */
+	rcu_dynticks_eqs_enter();
+}
+
 /**
  * rcu_irq_exit - inform RCU that current CPU is exiting irq towards idle
  *
@@ -1012,6 +1050,43 @@ void rcu_user_exit(void)
 }
 #endif /* CONFIG_NO_HZ_FULL */
 
+/**
+ * rcu_nmi_enter - inform RCU of entry to NMI context
+ *
+ * If the CPU was idle from RCU's viewpoint, update rdtp->dynticks and
+ * rdtp->dynticks_nmi_nesting to let the RCU grace-period handling know
+ * that the CPU is active.  This implementation permits nested NMIs, as
+ * long as the nesting level does not overflow an int.  (You will probably
+ * run out of stack space first.)
+ *
+ * If you add or remove a call to rcu_nmi_enter(), be sure to test
+ * with CONFIG_RCU_EQS_DEBUG=y.
+ */
+void rcu_nmi_enter(void)
+{
+	struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);
+	int incby = 2;
+
+	/* Complain about underflow. */
+	WARN_ON_ONCE(rdtp->dynticks_nmi_nesting < 0);
+
+	/*
+	 * If idle from RCU viewpoint, atomically increment ->dynticks
+	 * to mark non-idle and increment ->dynticks_nmi_nesting by one.
+	 * Otherwise, increment ->dynticks_nmi_nesting by two.  This means
+	 * if ->dynticks_nmi_nesting is equal to one, we are guaranteed
+	 * to be in the outermost NMI handler that interrupted an RCU-idle
+	 * period (observation due to Andy Lutomirski).
+	 */
+	if (rcu_dynticks_curr_cpu_in_eqs()) {
+		rcu_dynticks_eqs_exit();
+		incby = 1;
+	}
+	WRITE_ONCE(rdtp->dynticks_nmi_nesting, /* Prevent store tearing. */
+		   rdtp->dynticks_nmi_nesting + incby);
+	barrier();
+}
+
 /**
  * rcu_irq_enter - inform RCU that current CPU is entering irq away from idle
  *
@@ -1070,81 +1145,6 @@ void rcu_irq_enter_irqson(void)
 	local_irq_restore(flags);
 }
 
-/**
- * rcu_nmi_enter - inform RCU of entry to NMI context
- *
- * If the CPU was idle from RCU's viewpoint, update rdtp->dynticks and
- * rdtp->dynticks_nmi_nesting to let the RCU grace-period handling know
- * that the CPU is active.  This implementation permits nested NMIs, as
- * long as the nesting level does not overflow an int.  (You will probably
- * run out of stack space first.)
- *
- * If you add or remove a call to rcu_nmi_enter(), be sure to test
- * with CONFIG_RCU_EQS_DEBUG=y.
- */
-void rcu_nmi_enter(void)
-{
-	struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);
-	int incby = 2;
-
-	/* Complain about underflow. */
-	WARN_ON_ONCE(rdtp->dynticks_nmi_nesting < 0);
-
-	/*
-	 * If idle from RCU viewpoint, atomically increment ->dynticks
-	 * to mark non-idle and increment ->dynticks_nmi_nesting by one.
-	 * Otherwise, increment ->dynticks_nmi_nesting by two.  This means
-	 * if ->dynticks_nmi_nesting is equal to one, we are guaranteed
-	 * to be in the outermost NMI handler that interrupted an RCU-idle
-	 * period (observation due to Andy Lutomirski).
-	 */
-	if (rcu_dynticks_curr_cpu_in_eqs()) {
-		rcu_dynticks_eqs_exit();
-		incby = 1;
-	}
-	WRITE_ONCE(rdtp->dynticks_nmi_nesting, /* Prevent store tearing. */
-		   rdtp->dynticks_nmi_nesting + incby);
-	barrier();
-}
-
-/**
- * rcu_nmi_exit - inform RCU of exit from NMI context
- *
- * If we are returning from the outermost NMI handler that interrupted an
- * RCU-idle period, update rdtp->dynticks and rdtp->dynticks_nmi_nesting
- * to let the RCU grace-period handling know that the CPU is back to
- * being RCU-idle.
- *
- * If you add or remove a call to rcu_nmi_exit(), be sure to test
- * with CONFIG_RCU_EQS_DEBUG=y.
- */
-void rcu_nmi_exit(void)
-{
-	struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);
-
-	/*
-	 * Check for ->dynticks_nmi_nesting underflow and bad ->dynticks.
-	 * (We are exiting an NMI handler, so RCU better be paying attention
-	 * to us!)
-	 */
-	WARN_ON_ONCE(rdtp->dynticks_nmi_nesting <= 0);
-	WARN_ON_ONCE(rcu_dynticks_curr_cpu_in_eqs());
-
-	/*
-	 * If the nesting level is not 1, the CPU wasn't RCU-idle, so
-	 * leave it in non-RCU-idle state.
-	 */
-	if (rdtp->dynticks_nmi_nesting != 1) {
-		WRITE_ONCE(rdtp->dynticks_nmi_nesting, /* No store tearing. */
-			   rdtp->dynticks_nmi_nesting - 2);
-		return;
-	}
-
-	/* This NMI interrupted an RCU-idle CPU, restore RCU-idleness. */
-	WRITE_ONCE(rdtp->dynticks_nmi_nesting, 0); /* Avoid store tearing. */
-	rcu_dynticks_eqs_enter();
-}
-
 /**
  * rcu_is_watching - see if RCU thinks that the current CPU is idle
  *