netdev - Re: [PATCH v6 bpf-next 1/3] bpf: enable BPF_PROG_TEST_RUN for raw

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Date:   Tue, 29 Sep 2020 11:24:06 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Song Liu <songliubraving@...com>
Cc:     Network Development <netdev@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>, Kernel Team <kernel-team@...com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...omium.org>,
        Andrii Nakryiko <andriin@...com>
Subject: Re: [PATCH v6 bpf-next 1/3] bpf: enable BPF_PROG_TEST_RUN for raw_tracepoint

On Fri, Sep 25, 2020 at 1:55 PM Song Liu <songliubraving@...com> wrote:
> +
> +       if ((kattr->test.flags & BPF_F_TEST_RUN_ON_CPU) == 0 ||
> +           cpu == smp_processor_id()) {
> +               __bpf_prog_test_run_raw_tp(&info);

That's broken:
[   35.874974] BUG: using smp_processor_id() in preemptible [00000000]
code: new_name/87
[   35.893983] caller is bpf_prog_test_run_raw_tp+0xd4/0x1b0
[   35.900124] CPU: 1 PID: 87 Comm: new_name Not tainted 5.9.0-rc6-g615bd02bf #1
[   35.907358] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
BIOS 1.10.2-1ubuntu1 04/01/2014
[   35.916941] Call Trace:
[   35.919660]  dump_stack+0x77/0x9b
[   35.923273]  check_preemption_disabled+0xb4/0xc0
[   35.928376]  bpf_prog_test_run_raw_tp+0xd4/0x1b0
[   35.933872]  ? selinux_bpf+0xd/0x70
[   35.937532]  __do_sys_bpf+0x6bb/0x21e0
[   35.941570]  ? find_held_lock+0x2d/0x90
[   35.945687]  ? vfs_write+0x150/0x220
[   35.949586]  do_syscall_64+0x2d/0x40
[   35.953443]  entry_SYSCALL_64_after_hwframe+0x44/0xa9

Please fix and add debug flags to your .config.