Hi Naveen,

On Tue, 12 Dec 2023 14:26:07 +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").

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

.../ftrace/test.d/ftrace/func_hotplug.tc | 30 +++++++++++++++++++ 1 file changed, 30 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..49731a2b5c23 --- /dev/null +++ b/tools/testing/selftests/ftrace/test.d/ftrace/func_hotplug.tc @@ -0,0 +1,30 @@ +#!/bin/sh +# SPDX-License-Identifier: GPL-2.0 +# 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 can not test cpu hotplug in UP environment"
• exit_unresolved

+fi

This looks good, but can you find the 2nd online CPU before this test? I mean, there is a case that cpu1 is already offlined and others like cpu2 is onlined. So we need to use the 2nd online cpu.

Thank you,

+echo 0 > tracing_on +echo > trace +: "Set CPU1 offline/online with function tracer enabled" +echo function > current_tracer +echo 1 > tracing_on +(echo 0 > /sys/devices/system/cpu/cpu1/online) +(echo "forked"; sleep 1) +(echo 1 > /sys/devices/system/cpu/cpu1/online) +echo 0 > tracing_on

+: "Check CPU1 events are recorded" +grep -q -e "[001]" trace

base-commit: b85ea95d086471afb4ad062012a4d73cd328fa86

2.43.0