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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Jesper Dangaard Brouer <hawk@kernel.org>
Cc: netdev@vger.kernel.org, bpf@vger.kernel.org,
	"David S. Miller" <davem@davemloft.net>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>,
	John Fastabend <john.fastabend@gmail.com>,
	Paolo Abeni <pabeni@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH net v2 0/3] Add missing xdp_do_flush() invocations.
Message-ID: <20230920075418.TdZ0jsM_@linutronix.de>
References: <20230918153611.165722-1-bigeasy@linutronix.de>
 <cb2f7931-5ae5-8583-acff-4a186fed6632@kernel.org>
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On 2023-09-20 09:04:27 [+0200], Jesper Dangaard Brouer wrote:
> Hi Sebastian,

Hi Jesper,

> On 18/09/2023 17.36, Sebastian Andrzej Siewior wrote:
> > Hi,
> >=20
> > I've been looking at the drivers/ XDP users and noticed that some
> > XDP_REDIRECT user don't invoke xdp_do_flush() at the end.
>=20
> I'm wondering if we could detect (and WARN) in the net core e.g.
> net_rx_action() that a driver is missing a flush?
>=20
> The idea could be to check the per CPU (struct) bpf_redirect_info.
> Or check (per CPU) dev_flush_list.
>=20
> If some is worried about performance implications, then we can hide this
> under CONFIG_DEBUG_NET.

I had a WARN_ON in mind since the list has to be empty after the
completion of a NAPI callback. Now that you are bringing it up let me
actually do something=E2=80=A6

> --Jesper

Sebastian