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]
--- Changes in v5: - Rebased on top of net-next. - Calling bpftrace_stop using the defer helper. (Willem) - Link to v4: https://lore.kernel.org/r/20250702-netpoll_test-v4-0-cec227e85639@debian.org
Changes in v4: - Make the test XFail if it doesn't hit the function we are looking for - Toggle the interface while the traffic is flowing. - Bumped the number of messages from 10 to 40 per iterations. * This is hitting ~15 times per run on my vng test. - Decreased the time from 15 seconds to 10 seconds, given that if it didn't hit the function in 10 seconds, 5 seconds extra will not help. - Link to v3: https://lore.kernel.org/r/20250627-netpoll_test-v3-0-575bd200c8a9@debian.org
Changes in v3: - Make pylint happy (Simon) - Remove the unnecessary patch in bpftrace to raise an exception when it fails. (Jakub) - Improved the bpftrace code (Willem) - Stop sending messages if bpftrace is not alive anymore. - Link to v2: https://lore.kernel.org/r/20250625-netpoll_test-v2-0-47d27775222c@debian.org
Changes in v2: - Stole Jakub's helper to run bpftrace - Removed the DEBUG option and moved logs to logging - Change the code to have a higher chance of calling netpoll_poll_dev(). In my current configuration, it is hitting multiple times during the test. - Save and restore TX/RX queue size (Jakub) - Link to v1: https://lore.kernel.org/r/20250620-netpoll_test-v1-1-5068832f72fc@debian.org
--- Breno Leitao (2): selftests: drv-net: Strip '@' prefix from bpftrace map keys selftests: net: add netpoll basic functionality test
Jakub Kicinski (1): selftests: drv-net: add helper/wrapper for bpftrace
tools/testing/selftests/drivers/net/Makefile | 1 + .../selftests/drivers/net/lib/py/__init__.py | 3 +- .../testing/selftests/drivers/net/netpoll_basic.py | 366 +++++++++++++++++++++ tools/testing/selftests/net/lib/py/utils.py | 35 ++ 4 files changed, 404 insertions(+), 1 deletion(-) --- base-commit: 0234362d0af4649bc2ff745e94d06d0c6f0a46ce change-id: 20250612-netpoll_test-a1324d2057c8
Best regards, -- Breno Leitao leitao@debian.org