[PATCH 2/4] tracing: Fix graph tracer with stack tracer on other archs

From: Steven Rostedt
Date: Tue Jul 15 2014 - 23:26:44 EST

From: "Steven Rostedt (Red Hat)" <rostedt@xxxxxxxxxxx>

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

Cc: stable@xxxxxxxxxxxxxxx # 3.3+
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
kernel/trace/ftrace.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 5b372e3ed675..ac9d1dad630b 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -265,12 +265,12 @@ 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)

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

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