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References: <20230427234833.1576130-1-namhyung@kernel.org>
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From:   Ian Rogers <irogers@google.com>
Date:   Thu, 27 Apr 2023 17:32:08 -0700
Message-ID: <CAP-5=fX3pmozMci+hSSV3Nve6H6RUzusPY2_S7HeEtRJnZH7nA@mail.gmail.com>
Subject: Re: [PATCH 1/2] perf lock contention: Fix struct rq lock access
To:     Namhyung Kim <namhyung@kernel.org>
Cc:     Arnaldo Carvalho de Melo <acme@kernel.org>,
        Jiri Olsa <jolsa@kernel.org>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        linux-perf-users@vger.kernel.org, bpf@vger.kernel.org,
        Andrii Nakryiko <andrii@kernel.org>,
        Hao Luo <haoluo@google.com>, Song Liu <song@kernel.org>
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On Thu, Apr 27, 2023 at 4:48=E2=80=AFPM Namhyung Kim <namhyung@kernel.org> =
wrote:
>
> The BPF CO-RE's ignore suffix rule requires three underscores.
> Otherwise it'd fail like below:
>
>   $ sudo perf lock contention -ab
>   libbpf: prog 'collect_lock_syms': BPF program load failed: Invalid argu=
ment
>   libbpf: prog 'collect_lock_syms': -- BEGIN PROG LOAD LOG --
>   reg type unsupported for arg#0 function collect_lock_syms#380
>   ; int BPF_PROG(collect_lock_syms)
>   0: (b7) r6 =3D 0                        ; R6_w=3D0
>   1: (b7) r7 =3D 0                        ; R7_w=3D0
>   2: (b7) r9 =3D 1                        ; R9_w=3D1
>   3: <invalid CO-RE relocation>
>   failed to resolve CO-RE relocation <byte_off> [381] struct rq__new.__lo=
ck (0:0 @ offset 0)
>
> Fixes: 0c1228486bef ("perf lock contention: Support pre-5.14 kernels")
> Signed-off-by: Namhyung Kim <namhyung@kernel.org>

Acked-by: Ian Rogers <irogers@google.com>

Thanks,
Ian

> ---
>  tools/perf/util/bpf_skel/lock_contention.bpf.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/tools/perf/util/bpf_skel/lock_contention.bpf.c b/tools/perf/=
util/bpf_skel/lock_contention.bpf.c
> index 8911e2a077d8..30c193078bdb 100644
> --- a/tools/perf/util/bpf_skel/lock_contention.bpf.c
> +++ b/tools/perf/util/bpf_skel/lock_contention.bpf.c
> @@ -418,11 +418,11 @@ int contention_end(u64 *ctx)
>
>  extern struct rq runqueues __ksym;
>
> -struct rq__old {
> +struct rq___old {
>         raw_spinlock_t lock;
>  } __attribute__((preserve_access_index));
>
> -struct rq__new {
> +struct rq___new {
>         raw_spinlock_t __lock;
>  } __attribute__((preserve_access_index));
>
> @@ -434,8 +434,8 @@ int BPF_PROG(collect_lock_syms)
>
>         for (int i =3D 0; i < MAX_CPUS; i++) {
>                 struct rq *rq =3D bpf_per_cpu_ptr(&runqueues, i);
> -               struct rq__new *rq_new =3D (void *)rq;
> -               struct rq__old *rq_old =3D (void *)rq;
> +               struct rq___new *rq_new =3D (void *)rq;
> +               struct rq___old *rq_old =3D (void *)rq;
>
>                 if (rq =3D=3D NULL)
>                         break;
> --
> 2.40.1.495.gc816e09b53d-goog
>