rcu: Add tracing for RCU_FAST_NO_HZ

[deliverable/linux.git] / kernel / rcutree_plugin.h

diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index b70ca8cc52e17fc3d22940f546f7afb66debe394..6467f5669ab71c2b68996490ab0a2a2926cf7466 100644 (file)
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -2031,10 +2031,13 @@ static void rcu_prepare_for_idle(int cpu)
        /* If no callbacks or in the holdoff period, enter dyntick-idle. */
        if (!rcu_cpu_has_callbacks(cpu)) {
                per_cpu(rcu_dyntick_holdoff, cpu) = jiffies - 1;
+               trace_rcu_prep_idle("No callbacks");
                return;
        }
-       if (per_cpu(rcu_dyntick_holdoff, cpu) == jiffies)
+       if (per_cpu(rcu_dyntick_holdoff, cpu) == jiffies) {
+               trace_rcu_prep_idle("In holdoff");
                return;
+       }
 
        /* Check and update the rcu_dyntick_drain sequencing. */
        if (per_cpu(rcu_dyntick_drain, cpu) <= 0) {
@@ -2044,9 +2047,11 @@ static void rcu_prepare_for_idle(int cpu)
                /* We have hit the limit, so time to give up. */
                per_cpu(rcu_dyntick_holdoff, cpu) = jiffies;
                if (!rcu_pending(cpu)) {
+                       trace_rcu_prep_idle("Dyntick with callbacks");
                        per_cpu(rcu_awake_at_gp_end, cpu) = 1;
                        return;  /* Nothing to do immediately. */
                }
+               trace_rcu_prep_idle("Begin holdoff");
                invoke_rcu_core();  /* Force the CPU out of dyntick-idle. */
                return;
        }
@@ -2073,9 +2078,15 @@ static void rcu_prepare_for_idle(int cpu)
                c = c || per_cpu(rcu_bh_data, cpu).nxtlist;
        }
 
-       /* If RCU callbacks are still pending, RCU still needs this CPU. */
-       if (c)
+       /*
+        * If RCU callbacks are still pending, RCU still needs this CPU.
+        * So try forcing the callbacks through the grace period.
+        */
+       if (c) {
+               trace_rcu_prep_idle("More callbacks");
                invoke_rcu_core();
+       } else
+               trace_rcu_prep_idle("Callbacks drained");
 }
 
 /*
@@ -2085,6 +2096,7 @@ static void rcu_prepare_for_idle(int cpu)
  */
 static void rcu_wake_cpu(void *unused)
 {
+       trace_rcu_prep_idle("CPU awakened at GP end");
        invoke_rcu_core();
 }