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

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Message-ID: <20250626082505.GA183673@horms.kernel.org>
Date: Thu, 26 Jun 2025 09:25:05 +0100
From: Simon Horman <horms@...nel.org>
To: Breno Leitao <leitao@...ian.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 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)