netdev - Re: [PATCH net v2 0/3] Add missing xdp_do

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Date: Wed, 20 Sep 2023 09:54:18 +0200
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: Jesper Dangaard Brouer <hawk@...nel.org>
Cc: netdev@...r.kernel.org, bpf@...r.kernel.org,
	"David S. Miller" <davem@...emloft.net>,
	Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	John Fastabend <john.fastabend@...il.com>,
	Paolo Abeni <pabeni@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH net v2 0/3] Add missing xdp_do_flush() invocations.

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,
> > 
> > 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.
> 
> 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?
> 
> The idea could be to check the per CPU (struct) bpf_redirect_info.
> Or check (per CPU) dev_flush_list.
> 
> 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…

> --Jesper

Sebastian