netdev - Re: [RFC bpf-next 4/4] selftests/bpf: Add attach bench test

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Date:   Wed, 13 Apr 2022 12:02:22 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Masami Hiramatsu <mhiramat@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...omium.org>
Subject: Re: [RFC bpf-next 4/4] selftests/bpf: Add attach bench test

On Wed, Apr 13, 2022 at 9:59 AM Steven Rostedt <rostedt@...dmis.org> wrote:
>
> On Wed, 13 Apr 2022 09:45:52 -0700
> Andrii Nakryiko <andrii.nakryiko@...il.com> wrote:
>
> > > Did you only use the "notrace" on the prototype? I see the semicolon at
> > > the end of your comment. It only affects the actual function itself,
> > > not the prototype.
> >
> > notrace is both on declaration and on definition, see kernel/bpf/trampoline.c:
>
> OK. Note, it only needs to be on the function, the prototype doesn't do
> anything. But that shouldn't be the issue.
>
> >
> > void notrace __bpf_tramp_exit(struct bpf_tramp_image *tr)
> > {
> >         percpu_ref_put(&tr->pcref);
> > }
> >
>
> What compiler are you using? as this seems to be a compiler bug.
> Because it's not ftrace that picks what functions to trace, but the
> compiler itself.

I build my local kernel with

$ gcc --version
gcc (GCC) 11.1.1 20210623 (Red Hat 11.1.1-6)


But we have the same issue in our production kernels which are most
probably built with some other version of GCC, but I don't know which
one.


>
> -- Steve
>
>