ftrace/rcu: Do not trace debug_lockdep_rcu_enabled()

The function debug_lockdep_rcu_enabled() is part of the RCU lockdep
debugging, and is called very frequently. I found that if I enable
a lot of debugging and run the function graph tracer, this
function can cause a live lock of the system.

We don't usually trace lockdep infrastructure, no need to trace
this either.

Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c
index cce6ba8..4f20c6c 100644 (file)
--- a/kernel/rcupdate.c
+++ b/kernel/rcupdate.c
@@ -122,7 +122,7 @@ struct lockdep_map rcu_sched_lock_map =
        STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_sched", &rcu_sched_lock_key);
 EXPORT_SYMBOL_GPL(rcu_sched_lock_map);
 
-int debug_lockdep_rcu_enabled(void)
+int notrace debug_lockdep_rcu_enabled(void)
 {
        return rcu_scheduler_active && debug_locks &&
               current->lockdep_recursion == 0;