tracing: Allow benchmark to be enabled at early_initcall()

The trace event start up selftests fails when the trace benchmark is
enabled, because it is disabled during boot. It really only needs to be
disabled before scheduling is set up, as it creates a thread.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

kernel/trace/trace_benchmark.c

@@ -21,6 +21,8 @@ static u64 bm_stddev;
 static unsigned int bm_avg;
 static unsigned int bm_std;
 
+static bool ok_to_run;
+
 /*
  * This gets called in a loop recording the time it took to write
  * the tracepoint. What it writes is the time statistics of the last
@@ -166,7 +168,7 @@ static int benchmark_event_kthread(void *arg)
  */
 int trace_benchmark_reg(void)
 {
-	if (system_state != SYSTEM_RUNNING) {
+	if (!ok_to_run) {
 		pr_warning("trace benchmark cannot be started via kernel command line\n");
 		return -EBUSY;
 	}
@@ -207,3 +209,12 @@ void trace_benchmark_unreg(void)
 	bm_avg = 0;
 	bm_stddev = 0;
 }
+
+static __init int ok_to_run_trace_benchmark(void)
+{
+	ok_to_run = true;
+
+	return 0;
+}
+
+early_initcall(ok_to_run_trace_benchmark);