linux-kernel - Re: [PATCH] ftrace/selftest: Test combination of function

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Message-ID: <3901c521-be69-4824-a571-9182b9af02b6@linuxfoundation.org>
Date: Wed, 21 Aug 2024 21:54:42 -0600
From: Shuah Khan <skhan@...uxfoundation.org>
To: Steven Rostedt <rostedt@...dmis.org>, LKML
 <linux-kernel@...r.kernel.org>,
 Linux Trace Kernel <linux-trace-kernel@...r.kernel.org>
Cc: Masami Hiramatsu <mhiramat@...nel.org>,
 Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Mark Rutland <mark.rutland@....com>, Shuah Khan <shuah@...nel.org>,
 linux-kselftest@...r.kernel.org, Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH] ftrace/selftest: Test combination of function_graph
 tracer and function profiler

On 8/21/24 13:09, Steven Rostedt wrote:
> From: Steven Rostedt <rostedt@...dmis.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
> 
> Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.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?
> +
> +exit 0

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

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

thanks,
-- Shuah