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From:   Alexei Starovoitov <alexei.starovoitov@gmail.com>
Date:   Sat, 15 Jun 2019 16:35:12 -0700
Message-ID: <CAADnVQ+tPkiuYHPAE28OP3BDRgM+JY5DpTLiFP1iUn9fXhCjYQ@mail.gmail.com>
Subject: Re: [PATCH bpf v2] bpf: fix nested bpf tracepoints with per-cpu data
To:     Matt Mullins <mmullins@fb.com>
Cc:     Andrew Hall <hall@fb.com>, Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        bpf <bpf@vger.kernel.org>,
        Network Development <netdev@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Ingo Molnar <mingo@redhat.com>,
        Martin KaFai Lau <kafai@fb.com>,
        Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>
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On Tue, Jun 11, 2019 at 2:54 PM Matt Mullins <mmullins@fb.com> wrote:
>
> BPF_PROG_TYPE_RAW_TRACEPOINTs can be executed nested on the same CPU, as
> they do not increment bpf_prog_active while executing.
>
> This enables three levels of nesting, to support
>   - a kprobe or raw tp or perf event,
>   - another one of the above that irq context happens to call, and
>   - another one in nmi context
> (at most one of which may be a kprobe or perf event).
>
> Fixes: 20b9d7ac4852 ("bpf: avoid excessive stack usage for perf_sample_data")
> Signed-off-by: Matt Mullins <mmullins@fb.com>

Applied. Thanks