rcu: Add const annotation to char * for RCU tracepoints and functions

All the RCU tracepoints and functions that reference char pointers do
so with just 'char *' even though they do not modify the contents of
the string itself. This will cause warnings if a const char * is used
in one of these functions.

The RCU tracepoints store the pointer to the string to refer back to them
when the trace output is displayed. As this can be minutes, hours or
even days later, those strings had better be constant.

This change also opens the door to allow the RCU tracepoint strings and
their addresses to be exported so that userspace tracing tools can
translate the contents of the pointers of the RCU tracepoints.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 068de3a93606..30201494560b 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -1032,7 +1032,7 @@ static unsigned long rcu_cbs_completed(struct rcu_state *rsp,
  * rcu_nocb_wait_gp().
  */
 static void trace_rcu_future_gp(struct rcu_node *rnp, struct rcu_data *rdp,
-                                unsigned long c, char *s)
+                                unsigned long c, const char *s)
 {
         trace_rcu_future_grace_period(rdp->rsp->name, rnp->gpnum,
                                       rnp->completed, c, rnp->level,
@@ -2720,7 +2720,7 @@ static int rcu_cpu_has_callbacks(int cpu, bool *all_lazy)
  * Helper function for _rcu_barrier() tracing.  If tracing is disabled,
  * the compiler is expected to optimize this away.
  */
-static void _rcu_barrier_trace(struct rcu_state *rsp, char *s,
+static void _rcu_barrier_trace(struct rcu_state *rsp, const char *s,
                                int cpu, unsigned long done)
 {
         trace_rcu_barrier(rsp->name, s, cpu,