1 files changed, 78 insertions, 23 deletions

diff --git a/kernel/trace/trace_osnoise.c b/kernel/trace/trace_osnoise.c
index 5e832e3edf1f..eb617ccb81f1 100644
--- a/kernel/trace/trace_osnoise.c
+++ b/kernel/trace/trace_osnoise.c
@@ -65,6 +65,24 @@ static bool osnoise_has_registered_instances(void)
 }
 
 /*
+ * osnoise_instance_registered - check if a tr is already registered
+ */
+static int osnoise_instance_registered(struct trace_array *tr)
+{
+	struct osnoise_instance *inst;
+	int found = 0;
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(inst, &osnoise_instances, list) {
+		if (inst->tr == tr)
+			found = 1;
+	}
+	rcu_read_unlock();
+
+	return found;
+}
+
+/*
  * osnoise_register_instance - register a new trace instance
  *
  * Register a trace_array *tr in the list of instances running
@@ -2102,6 +2120,16 @@ static int osnoise_workload_start(void)
 {
 	int retval;
 
+	/*
+	 * Instances need to be registered after calling workload
+	 * start. Hence, if there is already an instance, the
+	 * workload was already registered. Otherwise, this
+	 * code is on the way to register the first instance,
+	 * and the workload will start.
+	 */
+	if (osnoise_has_registered_instances())
+		return 0;
+
 	osn_var_reset_all();
 
 	retval = osnoise_hook_events();
@@ -2129,6 +2157,13 @@ static int osnoise_workload_start(void)
  */
 static void osnoise_workload_stop(void)
 {
+	/*
+	 * Instances need to be unregistered before calling
+	 * stop. Hence, if there is a registered instance, more
+	 * than one instance is running, and the workload will not
+	 * yet stop. Otherwise, this code is on the way to disable
+	 * the last instance, and the workload can stop.
+	 */
 	if (osnoise_has_registered_instances())
 		return;
 
@@ -2150,7 +2185,11 @@ static void osnoise_tracer_start(struct trace_array *tr)
 {
 	int retval;
 
-	if (osnoise_has_registered_instances())
+	/*
+	 * If the instance is already registered, there is no need to
+	 * register it again.
+	 */
+	if (osnoise_instance_registered(tr))
 		return;
 
 	retval = osnoise_workload_start();
@@ -2162,18 +2201,17 @@ static void osnoise_tracer_start(struct trace_array *tr)
 
 static void osnoise_tracer_stop(struct trace_array *tr)
 {
-	if (!osnoise_has_registered_instances())
-		return;
-
 	osnoise_unregister_instance(tr);
 	osnoise_workload_stop();
 }
 
 static int osnoise_tracer_init(struct trace_array *tr)
 {
-
-	/* Only allow one instance to enable this */
-	if (osnoise_has_registered_instances())
+	/*
+	 * Only allow osnoise tracer if timerlat tracer is not running
+	 * already.
+	 */
+	if (timerlat_enabled())
 		return -EBUSY;
 
 	tr->max_latency = 0;
@@ -2202,45 +2240,55 @@ static void timerlat_tracer_start(struct trace_array *tr)
 {
 	int retval;
 
-	if (osnoise_has_registered_instances())
+	/*
+	 * If the instance is already registered, there is no need to
+	 * register it again.
+	 */
+	if (osnoise_instance_registered(tr))
 		return;
 
-	osnoise_data.timerlat_tracer = 1;
-
 	retval = osnoise_workload_start();
 	if (retval)
-		goto out_err;
+		pr_err(BANNER "Error starting timerlat tracer\n");
 
 	osnoise_register_instance(tr);
 
 	return;
-out_err:
-	pr_err(BANNER "Error starting timerlat tracer\n");
 }
 
 static void timerlat_tracer_stop(struct trace_array *tr)
 {
 	int cpu;
 
-	if (!osnoise_has_registered_instances())
-		return;
-
-	for_each_online_cpu(cpu)
-		per_cpu(per_cpu_osnoise_var, cpu).sampling = 0;
+	osnoise_unregister_instance(tr);
 
-	osnoise_tracer_stop(tr);
+	/*
+	 * Instruct the threads to stop only if this is the last instance.
+	 */
+	if (!osnoise_has_registered_instances()) {
+		for_each_online_cpu(cpu)
+			per_cpu(per_cpu_osnoise_var, cpu).sampling = 0;
+	}
 
-	osnoise_data.timerlat_tracer = 0;
+	osnoise_workload_stop();
 }
 
 static int timerlat_tracer_init(struct trace_array *tr)
 {
-	/* Only allow one instance to enable this */
-	if (osnoise_has_registered_instances())
+	/*
+	 * Only allow timerlat tracer if osnoise tracer is not running already.
+	 */
+	if (osnoise_has_registered_instances() && !osnoise_data.timerlat_tracer)
 		return -EBUSY;
 
-	tr->max_latency = 0;
+	/*
+	 * If this is the first instance, set timerlat_tracer to block
+	 * osnoise tracer start.
+	 */
+	if (!osnoise_has_registered_instances())
+		osnoise_data.timerlat_tracer = 1;
 
+	tr->max_latency = 0;
 	timerlat_tracer_start(tr);
 
 	return 0;
@@ -2249,6 +2297,13 @@ static int timerlat_tracer_init(struct trace_array *tr)
 static void timerlat_tracer_reset(struct trace_array *tr)
 {
 	timerlat_tracer_stop(tr);
+
+	/*
+	 * If this is the last instance, reset timerlat_tracer allowing
+	 * osnoise to be started.
+	 */
+	if (!osnoise_has_registered_instances())
+		osnoise_data.timerlat_tracer = 0;
 }
 
 static struct tracer timerlat_tracer __read_mostly = {