Re: [PATCH v2] ftrace/selftest: Test combination of function_graph tracer and function profiler

[Shuah Khan <skhan@linuxfoundation.org>]

On 10/4/24 12:56, Steven Rostedt wrote:
> From: Steven Rostedt <rostedt@goodmis.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@goodmis.org>
> ---
> Changes since v1: https://lore.kernel.org/20240821150903.05c6cf96@gandalf.local.home
> 
> - Added comment to why we are doing a sleep 1
> 
> - Now that the fix is in mainline, we can add this to the selftests
> 
>   .../ftrace/test.d/ftrace/fgraph-profiler.tc   | 31 +++++++++++++++++++
>   1 file changed, 31 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..1580e4ef9739
> --- /dev/null
> +++ b/tools/testing/selftests/ftrace/test.d/ftrace/fgraph-profiler.tc
> @@ -0,0 +1,31 @@
> +#!/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

"to to" -< "to"

I noticed this during my commit checks. Please fix and send v3.

> +
> +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
> +
> +# Let it run for a bit to make sure nothing explodes
> +sleep 1
> +
> +exit 0