[PATCH tip/core/rcu 04/15] rcu: Tell the compiler that rcu_state_p is immutable

From: Paul E. McKenney
Date: Tue May 12 2015 - 17:39:52 EST

From: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>

This commit adds a "const" tag to the declarations of rcu_state_p,
which should allow the compiler to generate better code and also to
catch erroneous assignments to this variable.

Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
kernel/rcu/tree.c | 2 +-
kernel/rcu/tree_plugin.h | 4 ++--
2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 4d3299577d7b..bacba943a6da 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -110,7 +110,7 @@ struct rcu_state sname##_state = { \
RCU_STATE_INITIALIZER(rcu_sched, 's', call_rcu_sched);
RCU_STATE_INITIALIZER(rcu_bh, 'b', call_rcu_bh);

-static struct rcu_state *rcu_state_p;
+static struct rcu_state *const rcu_state_p;

/* Increase (but not decrease) the CONFIG_RCU_FANOUT_LEAF at boot time. */
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index 8f8142778684..18b057adc21a 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -100,7 +100,7 @@ static void __init rcu_bootup_announce_oddness(void)

RCU_STATE_INITIALIZER(rcu_preempt, 'p', call_rcu);
-static struct rcu_state *rcu_state_p = &rcu_preempt_state;
+static struct rcu_state *const rcu_state_p = &rcu_preempt_state;

static int rcu_preempted_readers_exp(struct rcu_node *rnp);
static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp,
@@ -834,7 +834,7 @@ void exit_rcu(void)

#else /* #ifdef CONFIG_PREEMPT_RCU */

-static struct rcu_state *rcu_state_p = &rcu_sched_state;
+static struct rcu_state *const rcu_state_p = &rcu_sched_state;

* Tell them what RCU they are running.

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