[PATCH 3.10 06/56] tracing: Fix graph tracer with stack tracer on other archs

Greg Kroah-Hartman
2014-07-26T19:01:59Z

From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org>

commit 5f8bf2d263a20b986225ae1ed7d6759dc4b93af9 upstream.

Running my ftrace tests on PowerPC, it failed the test that checks
if function_graph tracer is affected by the stack tracer. It was.
Looking into this, I found that the update_function_graph_func()
must be called even if the trampoline function is not changed.
This is because archs like PowerPC do not support ftrace_ops being
passed by assembly and instead uses a helper function (what the
trampoline function points to). Since this function is not changed
even when multiple ftrace_ops are added to the code, the test that
falls out before calling update_function_graph_func() will miss that
the update must still be done.

Call update_function_graph_function() for all calls to
update_ftrace_function()

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
kernel/trace/ftrace.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -331,12 +331,12 @@ static void update_ftrace_function(void)
func = ftrace_ops_list_func;
}

+ update_function_graph_func();
+
/* If there's no change, then do nothing more here */
if (ftrace_trace_function == func)
return;

- update_function_graph_func();
-
/*
* If we are using the list function, it doesn't care
* about the function_trace_ops.