linux-kernel - [for-next][PATCH 3/5] function_graph: Have selftest also emulate tr->reset() as it did with tr->init()

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Date:   Thu, 25 Apr 2019 12:28:11 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     linux-kernel@...r.kernel.org
Cc:     Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: [for-next][PATCH 3/5] function_graph: Have selftest also emulate tr->reset() as it did with
 tr->init()

From: "Steven Rostedt (VMware)" <rostedt@...dmis.org>

The function_graph boot up self test emulates the tr->init() function in
order to add a wrapper around the function graph tracer entry code to test
for lock ups and such. But it does not emulate the tr->reset(), and just
calls the function_graph tracer tr->reset() function which will use its own
fgraph_ops to unregister function tracing with. As the fgraph_ops is
becoming more meaningful with the register_ftrace_graph() and
unregister_ftrace_graph() functions, the two need to be the same. The
emulated tr->init() uses its own fgraph_ops descriptor, which means the
unregister_ftrace_graph() must use the same ftrace_ops, which the selftest
currently does not do. By emulating the tr->reset() as the selftest does
with the tr->init() it will be able to pass the same fgraph_ops descriptor
to the unregister_ftrace_graph() as it did with the register_ftrace_graph().

Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
---
 kernel/trace/trace_selftest.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/trace_selftest.c b/kernel/trace/trace_selftest.c
index 9d402e7fc949..69ee8ef12cee 100644
--- a/kernel/trace/trace_selftest.c
+++ b/kernel/trace/trace_selftest.c
@@ -792,7 +792,10 @@ trace_selftest_startup_function_graph(struct tracer *trace,
 	/* check the trace buffer */
 	ret = trace_test_buffer(&tr->trace_buffer, &count);

-	trace->reset(tr);
+	/* Need to also simulate the tr->reset to remove this fgraph_ops */
+	tracing_stop_cmdline_record();
+	unregister_ftrace_graph(&fgraph_ops);
+
 	tracing_start();

 	if (!ret && !count) {
-- 
2.20.1