ftrace: reset selftests

The tests may leave stuff in the buffers. This resets the buffers
after each test is run. If a test fails, it does not reset the
buffer to avoid touching a buffer that is corrupted.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

kernel/trace/trace.c

@@ -289,6 +289,13 @@ int register_tracer(struct tracer *type)
 			printk(KERN_CONT "FAILED!\n");
 			goto out;
 		}
+		/* Only reset on passing, to avoid touching corrupted buffers */
+		for_each_possible_cpu(i) {
+			data = tr->data[i];
+			if (!head_page(data))
+				continue;
+			tracing_reset(data);
+		}
 		printk(KERN_CONT "PASSED\n");
 	}
 #endif