[PATCH v2] selftests/ftrace: Add test to exercize function tracer across cpu hotplug

[PATCH v2] selftests/ftrace: Add test to exercize function tracer across cpu hotplug

[Naveen N Rao]

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>
---
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

Re: [PATCH v2] selftests/ftrace: Add test to exercize function tracer across cpu hotplug

[Masami Hiramatsu]

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
> 


-- 
Masami Hiramatsu (Google) <mhiramat@kernel.org>

Re: [PATCH v2] selftests/ftrace: Add test to exercize function tracer across cpu hotplug

[Steven Rostedt]

On Wed, 13 Dec 2023 21:54:50 +0900
Masami Hiramatsu (Google) <mhiramat@kernel.org> wrote:

> 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,
> 

Thanks Naveen and Masami!

Shuah, can you take this through your tree?

-- Steve

Re: [PATCH v2] selftests/ftrace: Add test to exercize function tracer across cpu hotplug

[Naveen N Rao]

Hi Shuah,

On Wed, Dec 13, 2023 at 10:06:29AM -0500, Steven Rostedt wrote:
> On Wed, 13 Dec 2023 21:54:50 +0900
> Masami Hiramatsu (Google) <mhiramat@kernel.org> wrote:
> 
> > 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,
> > 
> 
> Thanks Naveen and Masami!
> 
> Shuah, can you take this through your tree?

Can you please pick up this patch?

- Naveen