2023-12-12 09:04:16

by Naveen N Rao

Subject: [PATCH] selftests/ftrace: Add test to exercize function tracer across cpu hotplug

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 <[email protected]>
---
.../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
+
+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

2023-12-13 00:40:53

by Masami Hiramatsu

Subject: Re: [PATCH] selftests/ftrace: Add test to exercize function tracer across cpu hotplug

Hi Naveen,

On Tue, 12 Dec 2023 14:26:07 +0530
Naveen N Rao <[email protected]> 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 <[email protected]>
> ---
> .../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
>


--
Masami Hiramatsu (Google) <[email protected]>

2023-12-13 11:36:03

by Naveen N Rao

Subject: Re: [PATCH] selftests/ftrace: Add test to exercize function tracer across cpu hotplug

On Wed, Dec 13, 2023 at 09:40:38AM +0900, Masami Hiramatsu wrote:
> Hi Naveen,
>
> On Tue, 12 Dec 2023 14:26:07 +0530
> Naveen N Rao <[email protected]> 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 <[email protected]>
> > ---
> > .../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.

Good point, thanks. I will send a v2.

- Naveen