On Wed, 13 Dec 2023 17:08:02 +0530 Naveen N Rao naveen@kernel.org wrote:

Add a test to exercize cpu hotplug with the function tracer active to ensure that sensitive functions in idle path are excluded from being traced. This helps catch issues such as the one fixed by commit 4b3338aaa74d ("powerpc/ftrace: Fix stack teardown in ftrace_no_trace").

Looks good to me.

Acked-by: Masami Hiramatsu (Google) mhiramat@kernel.org

Thank you,

Signed-off-by: Naveen N Rao naveen@kernel.org

v2: Add a check for next available online cpu, as suggested by Masami.

.../ftrace/test.d/ftrace/func_hotplug.tc | 42 +++++++++++++++++++ 1 file changed, 42 insertions(+) create mode 100644 tools/testing/selftests/ftrace/test.d/ftrace/func_hotplug.tc

diff --git a/tools/testing/selftests/ftrace/test.d/ftrace/func_hotplug.tc b/tools/testing/selftests/ftrace/test.d/ftrace/func_hotplug.tc new file mode 100644 index 000000000000..ccfbfde3d942 --- /dev/null +++ b/tools/testing/selftests/ftrace/test.d/ftrace/func_hotplug.tc @@ -0,0 +1,42 @@ +#!/bin/sh +# SPDX-License-Identifier: GPL-2.0-or-later +# description: ftrace - function trace across cpu hotplug +# requires: function:tracer

+if ! which nproc ; then

• nproc() {
• ls -d /sys/devices/system/cpu/cpu[0-9]* | wc -l
• }

+fi

+NP=`nproc`

+if [ $NP -eq 1 ] ;then

• echo "We cannot test cpu hotplug in UP environment"
• exit_unresolved

+fi

+# Find online cpu +for i in /sys/devices/system/cpu/cpu[1-9]*; do

• if [ -f $i/online ] && [ "$(cat $i/online)" = "1" ]; then

• cpu=$i
  

• break
  

• fi

+done

+if [ -z "$cpu" ]; then

• echo "We cannot test cpu hotplug with a single cpu online"
• exit_unresolved

+fi

+echo 0 > tracing_on +echo > trace

+: "Set $(basename $cpu) offline/online with function tracer enabled" +echo function > current_tracer +echo 1 > tracing_on +(echo 0 > $cpu/online) +(echo "forked"; sleep 1) +(echo 1 > $cpu/online) +echo 0 > tracing_on +echo nop > current_tracer

base-commit: b85ea95d086471afb4ad062012a4d73cd328fa86

2.43.0