linux-kernel - Re: [PATCH net-next v2 4/4] selftests: net: add netpoll basic functionality test

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Message-ID: <aF62OJinqv+FVu1z@gmail.com>
Date: Fri, 27 Jun 2025 08:18:16 -0700
From: Breno Leitao <leitao@...ian.org>
To: Simon Horman <horms@...nel.org>
Cc: Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Shuah Khan <shuah@...nel.org>, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org, linux-kselftest@...r.kernel.org,
	Willem de Bruijn <willemdebruijn.kernel@...il.com>,
	bpf@...r.kernel.org, gustavold@...il.com
Subject: Re: [PATCH net-next v2 4/4] selftests: net: add netpoll basic
 functionality test

On Thu, Jun 26, 2025 at 09:25:05AM +0100, Simon Horman wrote:
> On Wed, Jun 25, 2025 at 04:39:49AM -0700, Breno Leitao wrote:
> > Add a basic selftest for the netpoll polling mechanism, specifically
> > targeting the netpoll poll() side.
> > 
> > The test creates a scenario where network transmission is running at
> > maximum speed, and netpoll needs to poll the NIC. This is achieved by:
> > 
> >   1. Configuring a single RX/TX queue to create contention
> >   2. Generating background traffic to saturate the interface
> >   3. Sending netconsole messages to trigger netpoll polling
> >   4. Using dynamic netconsole targets via configfs
> >   5. Delete and create new netconsole targets after some messages
> >   6. Start a bpftrace in parallel to make sure netpoll_poll_dev() is
> >      called
> >   7. If bpftrace exists and netpoll_poll_dev() was called, stop.
> > 
> > The test validates a critical netpoll code path by monitoring traffic
> > flow and ensuring netpoll_poll_dev() is called when the normal TX path
> > is blocked.
> > 
> > This addresses a gap in netpoll test coverage for a path that is
> > tricky for the network stack.
> > 
> > Signed-off-by: Breno Leitao <leitao@...ian.org>
> 
> Hi Breno,
> 
> As it looks like there will be another version,
> could you run pylint over this. The NIPA invocation says:
>
> 
>   ************* Module netpoll_basic
>   .../netpoll_basic.py:323:0: C0301: Line too long (111/100) (line-too-long)
>   .../netpoll_basic.py:27:0: E0611: No name 'bpftrace' in module 'lib.py' (no-name-in-module)
>   .../netpoll_basic.py:79:11: E0606: Possibly using variable 'rx_queue' before assignment (possibly-used-before-assignment)
>   .../netpoll_basic.py:79:21: E0606: Possibly using variable 'tx_queue' before assignment (possibly-used-before-assignment)
>   .../netpoll_basic.py:253:22: W0613: Unused argument 'netdevnl' (unused-argument)

Thanks for the report. I was able to reproduce them here. The next
version should be warning free. I hope. :-)

Thanks for the review,
--breno