Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Thu, 26 Sep 2019 09:20:56 -0700
From:   John Fastabend <john.fastabend@gmail.com>
To:     Allan Zhang <allanzhang@google.com>, daniel@iogearbox.net,
        songliubraving@fb.com, netdev@vger.kernel.org, bpf@vger.kernel.org
Cc:     linux-kernel@vger.kernel.org, Allan Zhang <allanzhang@google.com>,
        Stanislav Fomichev <sdf@google.com>,
        Eric Dumazet <edumazet@google.com>
Message-ID: <5d8ce5686ef9f_34102b0cab5805c4b6@john-XPS-13-9370.notmuch>
In-Reply-To: <20190925234312.94063-2-allanzhang@google.com>
References: <20190925234312.94063-1-allanzhang@google.com>
 <20190925234312.94063-2-allanzhang@google.com>
Subject: RE: [PATCH 1/1] bpf: Fix bpf_event_output re-entry issue
Mime-Version: 1.0
Content-Type: text/plain;
 charset=utf-8
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Allan Zhang wrote:
> BPF_PROG_TYPE_SOCK_OPS program can reenter bpf_event_output because it can
> be called from atomic and non-atomic contexts since we don't have
> bpf_prog_active to prevent it happen.
> 
> This patch enables 3 level of nesting to support normal, irq and nmi
> context.
> 
> We can easily reproduce the issue by running neper crr mode with 100 flows
> and 10 threads from neper client side.
> 
> Here is the whole stack dump:
> 
> [  515.228898] WARNING: CPU: 20 PID: 14686 at kernel/trace/bpf_trace.c:549 bpf_event_output+0x1f9/0x220
> [  515.228903] CPU: 20 PID: 14686 Comm: tcp_crr Tainted: G        W        4.15.0-smp-fixpanic #44
> [  515.228904] Hardware name: Intel TBG,ICH10/Ikaria_QC_1b, BIOS 1.22.0 06/04/2018
> [  515.228905] RIP: 0010:bpf_event_output+0x1f9/0x220

[...]
 
> Fixes: a5a3a828cd00 ("bpf: add perf event notificaton support for sock_ops")
> 
> Effort: BPF
> Signed-off-by: Allan Zhang <allanzhang@google.com>
> Reviewed-by: Stanislav Fomichev <sdf@google.com>
> Reviewed-by: Eric Dumazet <edumazet@google.com>
> ---

LGTM thanks.

Acked-by: John Fastabend <john.fastabend@gmail.com>