linux-kernel - Re: [PATCH net-next v2 0/4] selftest: net: Add selftest for netpoll

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Message-ID: <20250625184346.GM1562@horms.kernel.org>
Date: Wed, 25 Jun 2025 19:43:46 +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,
	Stanislav Fomichev <sdf@...ichev.me>
Subject: Re: [PATCH net-next v2 0/4] selftest: net: Add selftest for netpoll

+ Stan

On Wed, Jun 25, 2025 at 04:39:45AM -0700, Breno Leitao wrote:
> I am submitting a new selftest for the netpoll subsystem specifically
> targeting the case where the RX is polling in the TX path, which is
> a case that we don't have any test in the tree today. This is done when
> netpoll_poll_dev() called, and this test creates a scenario when that is
> probably.
> 
> The test does the following:
> 
> 1) Configuring a single RX/TX queue to increase contention on the
>    interface.
> 2) Generating background traffic to saturate the network, mimicking
>    real-world congestion.
> 3) Sending netconsole messages to trigger netpoll polling and monitor
>    its behavior.
> 4) Using dynamic netconsole targets via configfs, with the ability to
>    delete and recreate targets during the test.
> 5) Running bpftrace in parallel to verify that netpoll_poll_dev() is
>    called when expected. If it is called, then the test passes,
>    otherwise the test is marked as skipped.
> 
> In order to achieve it, I stole Jakub's bpftrace helper from [1], and
> did some small changes that I found useful to use the helper.
> 
> So, this patchset basically contains:
> 
> 1) The code stolen from Jakub
> 2) Improvements on bpftrace() helper
> 3) The selftest itself
> 
> Link: https://lore.kernel.org/all/20250421222827.283737-22-kuba@kernel.org/ [1]

Jakub, Stan, all,

It looks like bpftrace needs to be installed on the CI workers.
Currently they report something a lot like this:

# timeout set to 180
# selftests: drivers/net: netpoll_basic.py
# Exception in thread Thread-1:
# Traceback (most recent call last):
#   File "/usr/lib64/python3.9/threading.py", line 980, in _bootstrap_inner
#     self.run()
#   File "/usr/lib64/python3.9/threading.py", line 917, in run
#     self._target(*self._args, **self._kwargs)
#   File "/home/virtme/testing-17/tools/testing/selftests/drivers/net/./netpoll_basic.py", line 198, in bpftrace_call
#     MAPS = bpftrace(expr, timeout=BPFTRACE_TIMEOUT, json=True)
#   File "/home/virtme/testing-17/tools/testing/selftests/net/lib/py/utils.py", line 205, in bpftrace
#     cmd_obj = cmd(cmd_arr, ns=ns, host=host, shell=False)
#   File "/home/virtme/testing-17/tools/testing/selftests/net/lib/py/utils.py", line 60, in __init__
#     self.proc = subprocess.Popen(comm, shell=shell, stdout=subprocess.PIPE,
#   File "/usr/lib64/python3.9/subprocess.py", line 951, in __init__
#     self._execute_child(args, executable, preexec_fn, close_fds,
#   File "/usr/lib64/python3.9/subprocess.py", line 1837, in _execute_child
#     raise child_exception_type(errno_num, err_msg, err_filename)
# FileNotFoundError: [Errno 2] No such file or directory: 'bpftrace'
# TAP version 13
# 1..1
# # Exception| Traceback (most recent call last):
# # Exception|   File "/home/virtme/testing-17/tools/testing/selftests/net/lib/py/ksft.py", line 243, in ksft_run
# # Exception|     case(*args)
# # Exception|   File "/home/virtme/testing-17/tools/testing/selftests/drivers/net/./netpoll_basic.py", line 308, in test_netpoll
# # Exception|     do_netpoll_flush_monitored(cfg, netdevnl, ifname, target_name)
# # Exception|   File "/home/virtme/testing-17/tools/testing/selftests/drivers/net/./netpoll_basic.py", line 243, in do_netpoll_flush_monitored
# # Exception|     do_netpoll_flush(cfg, netdevnl, ifname, target_name)
# # Exception|   File "/home/virtme/testing-17/tools/testing/selftests/drivers/net/./netpoll_basic.py", line 278, in do_netpoll_flush
# # Exception|     if bpftrace_any_hit(join=False):
# # Exception|   File "/home/virtme/testing-17/tools/testing/selftests/drivers/net/./netpoll_basic.py", line 230, in bpftrace_any_hit
# # Exception|     raise KsftFailEx(f"bpftrace failed to run!?: {MAPS}")
# # Exception| net.lib.py.ksft.KsftFailEx: bpftrace failed to run!?: {}
# not ok 1 netpoll_basic.test_netpoll
# # Totals: pass:0 fail:1 xfail:0 xpass:0 skip:0 error:0