trace-cmd: add a function to create a top instance

We need a way to allow external applications to create an instance for doing
their tracing, so add a helper function that takes care of creating an instance,
setting it as the main instance and doing the heavy lifting of creating the
instance in the tracing directory.  Thanks,

Link: http://lkml.kernel.org/r/1448053053-24188-4-git-send-email-jbacik@fb.com

Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

2 files changed, 24 insertions, 3 deletions

diff --git a/trace-cmd.h b/trace-cmd.h
index 5c961088..e55513a5 100644
--- a/trace-cmd.h
+++ b/trace-cmd.h
@@ -124,6 +124,8 @@ int tracecmd_buffer_instances(struct tracecmd_input *handle);
 const char *tracecmd_buffer_instance_name(struct tracecmd_input *handle, int indx);
 struct tracecmd_input *tracecmd_buffer_instance_handle(struct tracecmd_input *handle, int indx);
 int tracecmd_is_buffer_instance(struct tracecmd_input *handle);
+void tracecmd_create_top_instance(char *name);
+void tracecmd_remove_instances(void);
 
 void tracecmd_set_ts_offset(struct tracecmd_input *handle, unsigned long long offset);
 void tracecmd_set_ts2secs(struct tracecmd_input *handle, unsigned long long hz);
diff --git a/trace-record.c b/trace-record.c
index 7b7da385..e6c056cf 100644
--- a/trace-record.c
+++ b/trace-record.c
@@ -3669,7 +3669,7 @@ static void make_instances(void)
 	}
 }
 
-static void remove_instances(void)
+void tracecmd_remove_instances(void)
 {
 	struct buffer_instance *instance;
 	char *path;
@@ -3691,6 +3691,25 @@ static void remove_instances(void)
 	}
 }
 
+/**
+ * tracecmd_create_top_instance - create a top named instance
+ * @name: name of the instance to use.
+ *
+ * This is a library function for tools that want to do their tracing inside of
+ * an instance.  All it does is create an instance and set it as a top instance,
+ * you don't want to call this more than once, and you want to call
+ * tracecmd_remove_instances to undo your work.
+ */
+void tracecmd_create_top_instance(char *name)
+{
+	struct buffer_instance *instance;
+
+	instance = create_instance(name);
+	add_instance(instance);
+	update_first_instance(instance, 0);
+	make_instances();
+}
+
 static void check_plugin(const char *plugin)
 {
 	char *buf;
@@ -4319,7 +4338,7 @@ void trace_record (int argc, char **argv)
 		set_buffer_size();
 		clear_filters();
 		clear_triggers();
-		remove_instances();
+		tracecmd_remove_instances();
 		clear_func_filters();
 		exit(0);
 	} else
@@ -4795,7 +4814,7 @@ void trace_record (int argc, char **argv)
 
 	set_plugin("nop");
 
-	remove_instances();
+	tracecmd_remove_instances();
 
 	/* If tracing_on was enabled before we started, set it on now */
 	for_all_instances(instance) {