[PATCH v2] ftrace/selftest: Test combination of function_graph tracer and function profiler

[Steven Rostedt <rostedt@goodmis.org>]

From: Steven Rostedt <rostedt@goodmis.org>

Masami reported a bug when running function graph tracing then the
function profiler. The following commands would cause a kernel crash:

  # cd /sys/kernel/tracing/
  # echo function_graph > current_tracer
  # echo 1 > function_profile_enabled

In that order. Create a test to test this two to make sure this does not
come back as a regression.

Link: https://lore.kernel.org/172398528350.293426.8347220120333730248.stgit@devnote2

Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
Changes since v1: https://lore.kernel.org/20240821150903.05c6cf96@gandalf.local.home

- Added comment to why we are doing a sleep 1

- Now that the fix is in mainline, we can add this to the selftests

 .../ftrace/test.d/ftrace/fgraph-profiler.tc   | 31 +++++++++++++++++++
 1 file changed, 31 insertions(+)
 create mode 100644 tools/testing/selftests/ftrace/test.d/ftrace/fgraph-profiler.tc

diff --git a/tools/testing/selftests/ftrace/test.d/ftrace/fgraph-profiler.tc b/tools/testing/selftests/ftrace/test.d/ftrace/fgraph-profiler.tc
new file mode 100644
index 000000000000..1580e4ef9739
--- /dev/null
+++ b/tools/testing/selftests/ftrace/test.d/ftrace/fgraph-profiler.tc
@@ -0,0 +1,31 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+# description: ftrace - function profiler with function graph tracing
+# requires: function_profile_enabled set_ftrace_filter function_graph:tracer
+
+# The function graph tracer can now be run along side of the function
+# profiler. But there was a bug that caused the combination of the two
+# to crash. It also required the function graph tracer to be started
+# first.
+#
+# This test triggers that bug
+#
+# We need function_graph and profiling to to run this test
+
+fail() { # mesg
+    echo $1
+    exit_fail
+}
+
+echo "Enabling function graph tracer:"
+echo function_graph > current_tracer
+echo "enable profiler"
+
+# Older kernels do not allow function_profile to be enabled with
+# function graph tracer. If the below fails, mark it as unsupported
+echo 1 > function_profile_enabled || exit_unsupported
+
+# Let it run for a bit to make sure nothing explodes
+sleep 1
+
+exit 0
-- 
2.45.2