tracing: Add function-trace option to disable function tracing of latency tracers

[~andy/linux] / kernel / trace / trace_sched_wakeup.c

diff --git a/kernel/trace/trace_sched_wakeup.c b/kernel/trace/trace_sched_wakeup.c
index c16f8cd63c3ca9237743a43e6b38667f1055d3a0..fee77e15d8154e5a9a7936824b14b6d805c0dc13 100644 (file)
--- a/kernel/trace/trace_sched_wakeup.c
+++ b/kernel/trace/trace_sched_wakeup.c
@@ -37,6 +37,7 @@ static int wakeup_graph_entry(struct ftrace_graph_ent *trace);
 static void wakeup_graph_return(struct ftrace_graph_ret *trace);
 
 static int save_flags;
+static bool function_enabled;
 
 #define TRACE_DISPLAY_GRAPH     1
 
@@ -134,15 +135,60 @@ static struct ftrace_ops trace_ops __read_mostly =
 };
 #endif /* CONFIG_FUNCTION_TRACER */
 
-static int start_func_tracer(int graph)
+static int register_wakeup_function(int graph, int set)
 {
        int ret;
 
-       if (!graph)
-               ret = register_ftrace_function(&trace_ops);
-       else
+       /* 'set' is set if TRACE_ITER_FUNCTION is about to be set */
+       if (function_enabled || (!set && !(trace_flags & TRACE_ITER_FUNCTION)))
+               return 0;
+
+       if (graph)
                ret = register_ftrace_graph(&wakeup_graph_return,
                                            &wakeup_graph_entry);
+       else
+               ret = register_ftrace_function(&trace_ops);
+
+       if (!ret)
+               function_enabled = true;
+
+       return ret;
+}
+
+static void unregister_wakeup_function(int graph)
+{
+       if (!function_enabled)
+               return;
+
+       if (graph)
+               unregister_ftrace_graph();
+       else
+               unregister_ftrace_function(&trace_ops);
+
+       function_enabled = false;
+}
+
+static void wakeup_function_set(int set)
+{
+       if (set)
+               register_wakeup_function(is_graph(), 1);
+       else
+               unregister_wakeup_function(is_graph());
+}
+
+static int wakeup_flag_changed(struct tracer *tracer, u32 mask, int set)
+{
+       if (mask & TRACE_ITER_FUNCTION)
+               wakeup_function_set(set);
+
+       return trace_keep_overwrite(tracer, mask, set);
+}
+
+static int start_func_tracer(int graph)
+{
+       int ret;
+
+       ret = register_wakeup_function(graph, 0);
 
        if (!ret && tracing_is_enabled())
                tracer_enabled = 1;
@@ -156,10 +202,7 @@ static void stop_func_tracer(int graph)
 {
        tracer_enabled = 0;
 
-       if (!graph)
-               unregister_ftrace_function(&trace_ops);
-       else
-               unregister_ftrace_graph();
+       unregister_wakeup_function(graph);
 }
 
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
@@ -600,7 +643,7 @@ static struct tracer wakeup_tracer __read_mostly =
        .print_line     = wakeup_print_line,
        .flags          = &tracer_flags,
        .set_flag       = wakeup_set_flag,
-       .flag_changed   = trace_keep_overwrite,
+       .flag_changed   = wakeup_flag_changed,
 #ifdef CONFIG_FTRACE_SELFTEST
        .selftest    = trace_selftest_startup_wakeup,
 #endif
@@ -622,7 +665,7 @@ static struct tracer wakeup_rt_tracer __read_mostly =
        .print_line     = wakeup_print_line,
        .flags          = &tracer_flags,
        .set_flag       = wakeup_set_flag,
-       .flag_changed   = trace_keep_overwrite,
+       .flag_changed   = wakeup_flag_changed,
 #ifdef CONFIG_FTRACE_SELFTEST
        .selftest    = trace_selftest_startup_wakeup,
 #endif