linux-kernel - [PATCH 3.15 016/109] tracing: Fix graph tracer with stack tracer on other archs

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Message-Id: <20140726190224.324068050@linuxfoundation.org>
Date:	Sat, 26 Jul 2014 12:01:38 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>
Subject: [PATCH 3.15 016/109] tracing: Fix graph tracer with stack tracer on other archs

3.15-stable review patch.  If anyone has any objections, please let me know.

------------------

From: "Steven Rostedt (Red Hat)" <rostedt@...dmis.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@...dmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

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

--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -325,12 +325,12 @@ 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.

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