2 files changed, 36 insertions, 4 deletions

diff --git a/include/trace/events/timer.h b/include/trace/events/timer.h
index 425bcfe56c62..f5eb53eb658f 100644
--- a/include/trace/events/timer.h
+++ b/include/trace/events/timer.h
@@ -323,6 +323,27 @@ TRACE_EVENT(itimer_expire,
                   (int) __entry->pid, (unsigned long long)__entry->now)
 );
 
+#ifdef CONFIG_NO_HZ_FULL
+TRACE_EVENT(tick_stop,
+
+        TP_PROTO(int success, char *error_msg),
+
+        TP_ARGS(success, error_msg),
+
+        TP_STRUCT__entry(
+                __field( int ,          success )
+                __string( msg,          error_msg )
+        ),
+
+        TP_fast_assign(
+                __entry->success        = success;
+                __assign_str(msg, error_msg);
+        ),
+
+        TP_printk("success=%s msg=%s",  __entry->success ? "yes" : "no", __get_str(msg))
+);
+#endif
+
 #endif /*  _TRACE_TIMER_H */
 
 /* This part must be outside protection */
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 12a900dbb819..85e05ab98253 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -28,6 +28,8 @@
 
 #include "tick-internal.h"
 
+#include <trace/events/timer.h>
+
 /*
  * Per cpu nohz control structure
  */
@@ -153,14 +155,20 @@ static bool can_stop_full_tick(void)
 {
         WARN_ON_ONCE(!irqs_disabled());
 
-        if (!sched_can_stop_tick())
+        if (!sched_can_stop_tick()) {
+                trace_tick_stop(0, "more than 1 task in runqueue\n");
                 return false;
+        }
 
-        if (!posix_cpu_timers_can_stop_tick(current))
+        if (!posix_cpu_timers_can_stop_tick(current)) {
+                trace_tick_stop(0, "posix timers running\n");
                 return false;
+        }
 
-        if (!perf_event_can_stop_tick())
+        if (!perf_event_can_stop_tick()) {
+                trace_tick_stop(0, "perf events running\n");
                 return false;
+        }
 
         /* sched_clock_tick() needs us? */
 #ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
@@ -168,8 +176,10 @@ static bool can_stop_full_tick(void)
          * TODO: kick full dynticks CPUs when
          * sched_clock_stable is set.
          */
-        if (!sched_clock_stable)
+        if (!sched_clock_stable) {
+                trace_tick_stop(0, "unstable sched clock\n");
                 return false;
+        }
 #endif
 
         return true;
@@ -631,6 +641,7 @@ static ktime_t tick_nohz_stop_sched_tick(struct tick_sched *ts,
 
                         ts->last_tick = hrtimer_get_expires(&ts->sched_timer);
                         ts->tick_stopped = 1;
+                        trace_tick_stop(1, " ");
                 }
 
                 /*