netdev - RE: [PATCH 1/1] bpf: Fix bpf_event

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Message-ID: <5d8ce5686ef9f_34102b0cab5805c4b6@john-XPS-13-9370.notmuch>
Date:   Thu, 26 Sep 2019 09:20:56 -0700
From:   John Fastabend <john.fastabend@...il.com>
To:     Allan Zhang <allanzhang@...gle.com>, daniel@...earbox.net,
        songliubraving@...com, netdev@...r.kernel.org, bpf@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, Allan Zhang <allanzhang@...gle.com>,
        Stanislav Fomichev <sdf@...gle.com>,
        Eric Dumazet <edumazet@...gle.com>
Subject: RE: [PATCH 1/1] bpf: Fix bpf_event_output re-entry issue

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@...gle.com>
> Reviewed-by: Stanislav Fomichev <sdf@...gle.com>
> Reviewed-by: Eric Dumazet <edumazet@...gle.com>
> ---

LGTM thanks.

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