linux-kernel - Re: [PATCH net-next v2] selftest: epoll_busy

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Date: Mon, 6 May 2024 18:40:00 -0700
From: Joe Damato <jdamato@...tly.com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: linux-kselftest@...r.kernel.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, nalramli@...tly.com,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>,
	Shuah Khan <shuah@...nel.org>
Subject: Re: [PATCH net-next v2] selftest: epoll_busy_poll: epoll busy poll
 tests

On Mon, May 06, 2024 at 06:12:54PM -0700, Jakub Kicinski wrote:
> On Mon,  6 May 2024 20:53:22 +0000 Joe Damato wrote:
> > Add a simple test for the epoll busy poll ioctls, using the kernel
> > selftest harness.
> > 
> > This test ensures that the ioctls have the expected return codes and
> > that the kernel properly gets and sets epoll busy poll parameters.
> > 
> > The test can be expanded in the future to do real busy polling (provided
> > another machine to act as the client is available).
> 
> Hm, we get:
> 
> # timeout set to 3600
> # selftests: net: epoll_busy_poll
> # TAP version 13
> # 1..5
> # # Starting 5 tests from 2 test cases.
> # #  RUN           invalid_fd.test_invalid_fd ...
> # #            OK  invalid_fd.test_invalid_fd
> # ok 1 invalid_fd.test_invalid_fd
> # #  RUN           epoll_busy_poll.test_get_params ...
> # #            OK  epoll_busy_poll.test_get_params
> # ok 2 epoll_busy_poll.test_get_params
> # #  RUN           epoll_busy_poll.test_set_invalid ...
> # # epoll_busy_poll.c:204:test_set_invalid:Expected -1 (-1) == ret (0)
> # # epoll_busy_poll.c:205:test_set_invalid:EPIOCSPARAMS should error busy_poll_budget > NAPI_POLL_WEIGHT
> # # epoll_busy_poll.c:207:test_set_invalid:Expected EPERM (1) == errno (22)
> # # epoll_busy_poll.c:208:test_set_invalid:EPIOCSPARAMS errno should be EPERM busy_poll_budget > NAPI_POLL_WEIGHT
> # # test_set_invalid: Test failed
> # #          FAIL  epoll_busy_poll.test_set_invalid
> # not ok 3 epoll_busy_poll.test_set_invalid
> # #  RUN           epoll_busy_poll.test_set_and_get_valid ...
> # #            OK  epoll_busy_poll.test_set_and_get_valid
> # ok 4 epoll_busy_poll.test_set_and_get_valid
> # #  RUN           epoll_busy_poll.test_invalid_ioctl ...
> # #            OK  epoll_busy_poll.test_invalid_ioctl
> # ok 5 epoll_busy_poll.test_invalid_ioctl
> 
> https://netdev-3.bots.linux.dev/vmksft-net/results/584001/98-epoll-busy-poll/stdout

Ah, sorry -- this is because I had assumed the test would run without
CAP_NET_ADMIN, but since:

  epoll_busy_poll.c:204:test_set_invalid:Expected -1 (-1) == ret (0)

succeeds (ret = 0), clearly I am mistaken. Sorry about that.

I think I'll spin up a v3 and I'll add a test with and without
CAP_NET_ADMIN to check both cases, which would probably be better anyway.