nohz: Add basic tracing

It's not obvious to find out why the full dynticks subsystem
doesn't always stop the tick: whether this is due to kthreads,
posix timers, perf events, etc...

These new tracepoints are here to help the user diagnose
the failures and test this feature.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Gilad Ben Yossef <gilad@benyossef.com>
Cc: Hakan Akkan <hakanakkan@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Kevin Hilman <khilman@linaro.org>
Cc: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 21 insertions, 0 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 */