netdev - Re: [PATCH v2 bpf-next 3/4] selftests/bpf: Add profiler test

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Date:   Tue, 13 Oct 2020 23:59:15 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     Andrii Nakryiko <andrii@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Daniel Borkmann <daniel@...earbox.net>,
        John Fastabend <john.fastabend@...il.com>,
        Network Development <netdev@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>, Kernel Team <kernel-team@...com>
Subject: Re: [PATCH v2 bpf-next 3/4] selftests/bpf: Add profiler test

On Tue, Oct 13, 2020 at 02:03:33PM -0700, Alexei Starovoitov wrote:
> On Tue, Oct 13, 2020 at 12:56 PM Jiri Olsa <jolsa@...hat.com> wrote:
> >
> > On Thu, Oct 08, 2020 at 06:12:39PM -0700, Alexei Starovoitov wrote:
> >
> > SNIP
> >
> > > +
> > > +#ifdef UNROLL
> > > +#pragma unroll
> > > +#endif
> > > +     for (int i = 0; i < MAX_CGROUPS_PATH_DEPTH; i++) {
> > > +             filepart_length =
> > > +                     bpf_probe_read_str(payload, MAX_PATH, BPF_CORE_READ(cgroup_node, name));
> > > +             if (!cgroup_node)
> > > +                     return payload;
> > > +             if (cgroup_node == cgroup_root_node)
> > > +                     *root_pos = payload - payload_start;
> > > +             if (filepart_length <= MAX_PATH) {
> > > +                     barrier_var(filepart_length);
> > > +                     payload += filepart_length;
> > > +             }
> > > +             cgroup_node = BPF_CORE_READ(cgroup_node, parent);
> > > +     }
> > > +     return payload;
> > > +}
> > > +
> > > +static ino_t get_inode_from_kernfs(struct kernfs_node* node)
> > > +{
> > > +     struct kernfs_node___52* node52 = (void*)node;
> > > +
> > > +     if (bpf_core_field_exists(node52->id.ino)) {
> > > +             barrier_var(node52);
> > > +             return BPF_CORE_READ(node52, id.ino);
> > > +     } else {
> > > +             barrier_var(node);
> > > +             return (u64)BPF_CORE_READ(node, id);
> > > +     }
> > > +}
> > > +
> > > +int pids_cgrp_id = 1;
> >
> >
> > hi,
> > I'm getting compilation failure with this:
> >
> >           CLNG-LLC [test_maps] profiler2.o
> >         In file included from progs/profiler2.c:6:
> >         progs/profiler.inc.h:246:5: error: redefinition of 'pids_cgrp_id' as different kind of symbol
> >         int pids_cgrp_id = 1;
> >             ^
> >         /home/jolsa/linux-qemu/tools/testing/selftests/bpf/tools/include/vmlinux.h:14531:2: note: previous definition is here
> >                 pids_cgrp_id = 11,
> 
> Interesting.
> You probably have CONFIG_CGROUP_PIDS in your .config?

yes

jirka


> I don't and bpf CI doesn't have it either, so this issue wasn't spotted earlier.
> 
> I can hard code 11, of course, but
> but maybe Andrii has a cool way to use co-re to deal with this?
> I think
> "extern bool CONFIG_CGROUP_PIDS __kconfig"
> won't work.
> A good opportunity to try to use bpf_core_enum_value_exists() ?
>