rcu: Add event tracing to dyntick_save_progress_counter().

This patch adds event tracing to dyntick_save_progress_counter() in the case
where it returns 1. I used the tracepoint string "dti" because this function
returns 1 in case the CPU is in dynticks idle mode.

Signed-off-by: Andreea-Cristina Bernat <bernat.ada@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

1 files changed, 6 insertions, 1 deletions

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index fca911b6b29c..c6fd0f15425c 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -772,7 +772,12 @@ static int dyntick_save_progress_counter(struct rcu_data *rdp,
 {
         rdp->dynticks_snap = atomic_add_return(0, &rdp->dynticks->dynticks);
         rcu_sysidle_check_cpu(rdp, isidle, maxj);
-        return (rdp->dynticks_snap & 0x1) == 0;
+        if ((rdp->dynticks_snap & 0x1) == 0) {
+                trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, TPS("dti"));
+                return 1;
+        } else {
+                return 0;
+        }
 }
 
 /*