tracing: do not update tracing_max_latency when tracer is stopped

The state of the function pair tracing_stop()/tracing_start() is
correctly considered when tracer data are updated. However, the global
and externally accessible variable tracing_max_latency is always updated
- even when tracing is stopped.

The update should only occur, if tracing was not stopped.

Signed-off-by: Carsten Emde <C.Emde@osadl.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 4 insertions, 2 deletions

diff --git a/kernel/trace/trace_sched_wakeup.c b/kernel/trace/trace_sched_wakeup.c
index 6e1529bc6172..26185d727676 100644
--- a/kernel/trace/trace_sched_wakeup.c
+++ b/kernel/trace/trace_sched_wakeup.c
@@ -162,8 +162,10 @@ probe_wakeup_sched_switch(struct rq *rq, struct task_struct *prev,
         if (!report_latency(delta))
                 goto out_unlock;
 
-        tracing_max_latency = delta;
-        update_max_tr(wakeup_trace, wakeup_task, wakeup_cpu);
+        if (likely(!is_tracing_stopped())) {
+                tracing_max_latency = delta;
+                update_max_tr(wakeup_trace, wakeup_task, wakeup_cpu);
+        }
 
 out_unlock:
         __wakeup_reset(wakeup_trace);