tracing: let user specify tracing_thresh after selecting function_graph

Currently, tracing_thresh works only if we specify it before selecting
function_graph tracer. If we do the opposite, tracing_thresh will change
it's value, but it will not be applied.
To fix it, we add update_thresh callback which is called whenever
tracing_thresh is updated and for function_graph tracer we register
handler which reinitializes tracer depending on tracing_thresh.

Link: http://lkml.kernel.org/p/20140718111727.GA3206@stfomichev-desktop.yandex.net

Signed-off-by: Stanislav Fomichev <stfomichev@yandex-team.ru>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index 2c944e6c4a9d..74d98820497c 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -475,6 +475,12 @@ static void graph_trace_reset(struct trace_array *tr)
         unregister_ftrace_graph();
 }
 
+int graph_trace_update_thresh(struct trace_array *tr)
+{
+        graph_trace_reset(tr);
+        return graph_trace_init(tr);
+}
+
 static int max_bytes_for_cpu;
 
 static enum print_line_t
@@ -1525,6 +1531,7 @@ static struct trace_event graph_trace_ret_event = {
 
 static struct tracer graph_trace __tracer_data = {
         .name           = "function_graph",
+        .update_thresh  = graph_trace_update_thresh,
         .open           = graph_trace_open,
         .pipe_open      = graph_trace_open,
         .close          = graph_trace_close,