Re: [PATCH v2 3/3] perf test: fix "trace summary" test for musl-based systems

[Ian Rogers]

On Tue, Apr 28, 2026 at 7:39 AM Martin Kaiser <martin@xxxxxxxxx> wrote:
>
> The trace summary test calls /bin/true and filters for open, read and
> close events. These events are coming from shared library loads.
>
> On a musl system, the loader and libc may point to the same file. true
> needs only libc, no further shared libraries are loaded at startup. The
> test fails since no open, read and close events are captured.
>
> root@host:~# ldd /bin/true
>         /lib/ld-musl-riscv64.so.1 (0x3fb8882000)
>         libc.so => /lib/ld-musl-riscv64.so.1 (0x3fb8882000)
>
> root@host:~# file /lib/ld-musl-riscv64.so.1
> /lib/ld-musl-riscv64.so.1: symbolic link to /usr/lib/libc.so
>
> root@host:~# strace -f /bin/true
> execve("/bin/true", ["/bin/true", ...], ... /* 18 vars */) = 1
> set_tid_address(0x3fa1f7bf70)           = 330
> mprotect(0x2ad6b8e000, 12288, PROT_READ) = 0
> exit_group(0)                           = ?
> +++ exited with 0 +++
>
> Run "cat /dev/null" instead of "true". This creates the required events
> regardless of the C library and it works for cat from busybox or from
> coreutils.
>
> Signed-off-by: Martin Kaiser <martin@xxxxxxxxx>
> ---
> v2:
> - use cat /dev/null, this works for busybox and coreutils
>
>  tools/perf/tests/shell/trace_summary.sh | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tools/perf/tests/shell/trace_summary.sh b/tools/perf/tests/shell/trace_summary.sh
> index 22e2651d5919..b80dea77cec6 100755
> --- a/tools/perf/tests/shell/trace_summary.sh
> +++ b/tools/perf/tests/shell/trace_summary.sh
> @@ -14,7 +14,7 @@ OUTPUT=$(mktemp /tmp/perf_trace_test.XXXXX)
>
>  test_perf_trace() {
>      args=$1
> -    workload="true"
> +    workload="cat /dev/null"

Could we capture why the unusual workload in a comment, I know it is
in the commit message.

Acked-by: Ian Rogers <irogers@xxxxxxxxxx>

Thanks,
Ian

>      search="^\s*(open|read|close).*[0-9]+%$"
>
>      echo "testing: perf trace ${args} -- ${workload}"
> --
> 2.43.7
>