tracing: Use one prologue for the wakeup tracer function tracers

The wakeup tracer has three types of function tracers. Normal
function tracer, function graph entry, and function graph return.
Each of these use a complex dance to prevent recursion and whether
to trace the data or not (depending on the wake_task variable).

This patch moves the duplicate code into a single routine, to
prevent future mistakes with modifying duplicate complex code.

Cc: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

kernel/trace/trace_sched_wakeup.c

@@ -56,43 +56,73 @@ static struct tracer_flags tracer_flags = {
 #define is_graph() (tracer_flags.val & TRACE_DISPLAY_GRAPH)
 
 #ifdef CONFIG_FUNCTION_TRACER
+
 /*
- * wakeup uses its own tracer function to keep the overhead down:
+ * Prologue for the wakeup function tracers.
+ *
+ * Returns 1 if it is OK to continue, and preemption
+ *            is disabled and data->disabled is incremented.
+ *         0 if the trace is to be ignored, and preemption
+ *            is not disabled and data->disabled is
+ *            kept the same.
+ *
+ * Note, this function is also used outside this ifdef but
+ *  inside the #ifdef of the function graph tracer below.
+ *  This is OK, since the function graph tracer is
+ *  dependent on the function tracer.
  */
-static void
-wakeup_tracer_call(unsigned long ip, unsigned long parent_ip)
+static int
+func_prolog_preempt_disable(struct trace_array *tr,
+			    struct trace_array_cpu **data,
+			    int *pc)
 {
-	struct trace_array *tr = wakeup_trace;
-	struct trace_array_cpu *data;
-	unsigned long flags;
 	long disabled;
 	int cpu;
-	int pc;
 
 	if (likely(!wakeup_task))
-		return;
+		return 0;
 
-	pc = preempt_count();
+	*pc = preempt_count();
 	preempt_disable_notrace();
 
 	cpu = raw_smp_processor_id();
 	if (cpu != wakeup_current_cpu)
 		goto out_enable;
 
-	data = tr->data[cpu];
-	disabled = atomic_inc_return(&data->disabled);
+	*data = tr->data[cpu];
+	disabled = atomic_inc_return(&(*data)->disabled);
 	if (unlikely(disabled != 1))
 		goto out;
 
-	local_irq_save(flags);
+	return 1;
 
-	trace_function(tr, ip, parent_ip, flags, pc);
+out:
+	atomic_dec(&(*data)->disabled);
+
+out_enable:
+	preempt_enable_notrace();
+	return 0;
+}
+
+/*
+ * wakeup uses its own tracer function to keep the overhead down:
+ */
+static void
+wakeup_tracer_call(unsigned long ip, unsigned long parent_ip)
+{
+	struct trace_array *tr = wakeup_trace;
+	struct trace_array_cpu *data;
+	unsigned long flags;
+	int pc;
+
+	if (!func_prolog_preempt_disable(tr, &data, &pc))
+		return;
 
+	local_irq_save(flags);
+	trace_function(tr, ip, parent_ip, flags, pc);
 	local_irq_restore(flags);
 
- out:
 	atomic_dec(&data->disabled);
- out_enable:
 	preempt_enable_notrace();
 }
 
@@ -154,32 +184,16 @@ static int wakeup_graph_entry(struct ftrace_graph_ent *trace)
 	struct trace_array *tr = wakeup_trace;
 	struct trace_array_cpu *data;
 	unsigned long flags;
-	long disabled;
-	int cpu, pc, ret = 0;
+	int pc, ret = 0;
 
-	if (likely(!wakeup_task))
+	if (!func_prolog_preempt_disable(tr, &data, &pc))
 		return 0;
 
-	pc = preempt_count();
-	preempt_disable_notrace();
-
-	cpu = raw_smp_processor_id();
-	if (cpu != wakeup_current_cpu)
-		goto out_enable;
-
-	data = tr->data[cpu];
-	disabled = atomic_inc_return(&data->disabled);
-	if (unlikely(disabled != 1))
-		goto out;
-
 	local_save_flags(flags);
 	ret = __trace_graph_entry(tr, trace, flags, pc);
-
-out:
 	atomic_dec(&data->disabled);
-
-out_enable:
 	preempt_enable_notrace();
+
 	return ret;
 }
 
@@ -188,31 +202,15 @@ static void wakeup_graph_return(struct ftrace_graph_ret *trace)
 	struct trace_array *tr = wakeup_trace;
 	struct trace_array_cpu *data;
 	unsigned long flags;
-	long disabled;
-	int cpu, pc;
+	int pc;
 
-	if (likely(!wakeup_task))
+	if (!func_prolog_preempt_disable(tr, &data, &pc))
 		return;
 
-	pc = preempt_count();
-	preempt_disable_notrace();
-
-	cpu = raw_smp_processor_id();
-	if (cpu != wakeup_current_cpu)
-		goto out_enable;
-
-	data = tr->data[cpu];
-	disabled = atomic_inc_return(&data->disabled);
-	if (unlikely(disabled != 1))
-		goto out;
-
 	local_save_flags(flags);
 	__trace_graph_return(tr, trace, flags, pc);
-
-out:
 	atomic_dec(&data->disabled);
 
-out_enable:
 	preempt_enable_notrace();
 	return;
 }