linux-kernel - Re: [PATCH bpf-next v3 2/2] selftests/bpf: Add stacktrace map lookup_and_delete

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Message-ID: <CAEf4BzbWOzwmsMhHmk_LbWUFM=Q2DwVsWWtoVD4ZjK672_XV9w@mail.gmail.com>
Date: Mon, 22 Sep 2025 13:59:10 -0700
From: Andrii Nakryiko <andrii.nakryiko@...il.com>
To: Leon Hwang <hffilwlqm@...il.com>
Cc: Tao Chen <chen.dylane@...ux.dev>, ast@...nel.org, daniel@...earbox.net, 
	john.fastabend@...il.com, andrii@...nel.org, martin.lau@...ux.dev, 
	eddyz87@...il.com, song@...nel.org, yonghong.song@...ux.dev, 
	kpsingh@...nel.org, sdf@...ichev.me, haoluo@...gle.com, jolsa@...nel.org, 
	bpf@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH bpf-next v3 2/2] selftests/bpf: Add stacktrace map
 lookup_and_delete_elem test case

On Sun, Sep 21, 2025 at 7:42 PM Leon Hwang <hffilwlqm@...il.com> wrote:
>
>
>
> On 20/9/25 23:52, Tao Chen wrote:
> > ...
> > test_stacktrace_map:PASS:compare_stack_ips stackmap vs. stack_amap 0 nsec
> > test_stacktrace_map:PASS:stack_key_map lookup 0 nsec
> > test_stacktrace_map:PASS:stackmap lookup and detele 0 nsec
> > test_stacktrace_map:PASS:stackmap lookup deleted stack_id 0 nsec
> >  #397     stacktrace_map:OK
> > ...
>
> As they suppose to pass, they are meaningless in the commit log.
>
> Please describe what the test is for and what it is doing instead.
>
> >
> > Signed-off-by: Tao Chen <chen.dylane@...ux.dev>
> > ---
> >  .../selftests/bpf/prog_tests/stacktrace_map.c | 22 ++++++++++++++++++-
> >  .../selftests/bpf/progs/test_stacktrace_map.c |  8 +++++++
> >  2 files changed, 29 insertions(+), 1 deletion(-)
> >
> > diff --git a/tools/testing/selftests/bpf/prog_tests/stacktrace_map.c b/tools/testing/selftests/bpf/prog_tests/stacktrace_map.c
> > index 84a7e405e91..7d38afe5cfc 100644
> > --- a/tools/testing/selftests/bpf/prog_tests/stacktrace_map.c
> > +++ b/tools/testing/selftests/bpf/prog_tests/stacktrace_map.c
> > @@ -3,7 +3,7 @@
> >
> >  void test_stacktrace_map(void)
> >  {
> > -     int control_map_fd, stackid_hmap_fd, stackmap_fd, stack_amap_fd;
> > +     int control_map_fd, stackid_hmap_fd, stackmap_fd, stack_amap_fd, stack_key_map_fd;
> >       const char *prog_name = "oncpu";
> >       int err, prog_fd, stack_trace_len;
> >       const char *file = "./test_stacktrace_map.bpf.o";
> > @@ -11,6 +11,9 @@ void test_stacktrace_map(void)
> >       struct bpf_program *prog;
> >       struct bpf_object *obj;
> >       struct bpf_link *link;
> > +     __u32 stack_id;
> > +     char val_buf[PERF_MAX_STACK_DEPTH *
> > +             sizeof(struct bpf_stack_build_id)];
>
> Nit: minor indentation issue here.
>
> 'val_buf' should stay on a single line, since up to 100 characters per
> line are allowed.
>
> NOTE: keep inverted Christmas tree style.

we don't really enforce this, no need to shift lines around just for
the reverse Christmas tree style

>
> Thanks,
> Leon
>
> >
> >       err = bpf_prog_test_load(file, BPF_PROG_TYPE_TRACEPOINT, &obj, &prog_fd);
> >       if (CHECK(err, "prog_load", "err %d errno %d\n", err, errno))
> > @@ -41,6 +44,10 @@ void test_stacktrace_map(void)
> >       if (CHECK_FAIL(stack_amap_fd < 0))
> >               goto disable_pmu;
> >
> > +     stack_key_map_fd = bpf_find_map(__func__, obj, "stack_key_map");
> > +     if (CHECK_FAIL(stack_key_map_fd < 0))
> > +             goto disable_pmu;
> > +
> >       /* give some time for bpf program run */
> >       sleep(1);
> >
>
> [...]