On 8/22/24 07:19, Steven Rostedt wrote:

On Wed, 21 Aug 2024 21:54:42 -0600
Shuah Khan [off-list ref] wrote:

quoted

On 8/21/24 13:09, Steven Rostedt wrote:

quoted

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 (local)

Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
   .../ftrace/test.d/ftrace/fgraph-profiler.tc   | 30 +++++++++++++++++++
   1 file changed, 30 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..62d44a1395da
--- /dev/null
+++ b/tools/testing/selftests/ftrace/test.d/ftrace/fgraph-profiler.tc

@@ -0,0 +1,30 @@
+#!/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
+
+sleep 1

Any specific reason for this sleep 1 - can you add a comment on top?

We add sleep 1 in several locations of the ftrace selftests to let the
tracing run for a bit just to see if it triggers anything. Otherwise the
clean up can happen before anything gets traced. Although, it's highly
unlikely in this case, but still.

I could add a comment if you want of just:

# let it run for a bit
sleep 1

quoted

quoted

+
+exit 0

Reviewed-by: Shuah Khan <skhan@linuxfoundation.org>

Let me know if you would like v2 for this to be taken through my tree.

I'll make a v2 if you want me to.

No need for a v2

thanks,
-- Shuah