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[68.197.162.46]) by smtp.gmail.com with ESMTPSA id af79cd13be357-7c096c10bf2sm429397885a.20.2025.02.19.10.39.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 19 Feb 2025 10:39:53 -0800 (PST) Date: Wed, 19 Feb 2025 13:39:51 -0500 From: Joe Damato To: Jakub Kicinski Cc: davem@davemloft.net, netdev@vger.kernel.org, edumazet@google.com, pabeni@redhat.com, andrew+netdev@lunn.ch, horms@kernel.org, shuah@kernel.org, hawk@kernel.org, petrm@nvidia.com, willemdebruijn.kernel@gmail.com Subject: Re: [PATCH net-next 2/4] selftests: drv-net: add a way to wait for a local process Message-ID: Mail-Followup-To: Joe Damato , Jakub Kicinski , davem@davemloft.net, netdev@vger.kernel.org, edumazet@google.com, pabeni@redhat.com, andrew+netdev@lunn.ch, horms@kernel.org, shuah@kernel.org, hawk@kernel.org, petrm@nvidia.com, willemdebruijn.kernel@gmail.com References: <20250218195048.74692-1-kuba@kernel.org> <20250218195048.74692-3-kuba@kernel.org> <20250218150512.282c94eb@kernel.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250218150512.282c94eb@kernel.org> On Tue, Feb 18, 2025 at 03:05:12PM -0800, Jakub Kicinski wrote: > On Tue, 18 Feb 2025 16:52:39 -0500 Joe Damato wrote: > > Removing this check causes a stack trace on my XDP-disabled kernel, > > whereas with the existing code it caused a skip. > > > > Maybe that's OK, though? > > > > The issue is that xdp_helper.c fails and exits with return -1 before > > the call to ksft_ready() which results in the following: > > > > # Exception| Traceback (most recent call last): > > # Exception| File "/home/jdamato/code/net-next/tools/testing/selftests/net/lib/py/ksft.py", line 223, in ksft_run > > # Exception| case(*args) > > # Exception| File "/home/jdamato/code/net-next/./tools/testing/selftests/drivers/net/queues.py", line 27, in check_xsk > > # Exception| with bkg(f'{cfg.rpath("xdp_helper")} {cfg.ifindex} {xdp_queue_id}', > > # Exception| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > > # Exception| File "/home/jdamato/code/net-next/tools/testing/selftests/net/lib/py/utils.py", line 108, in __init__ > > # Exception| super().__init__(comm, background=True, > > # Exception| File "/home/jdamato/code/net-next/tools/testing/selftests/net/lib/py/utils.py", line 63, in __init__ > > # Exception| raise Exception("Did not receive ready message") > > # Exception| Exception: Did not receive ready message > > not ok 4 queues.check_xsk > > # Totals: pass:3 fail:1 xfail:0 xpass:0 skip:0 error:0 > > > > I had originally modified the test so that if XDP is disabled in the > > kernel it would skip, but I think you mentioned in a previous thread > > that this was a "non-goal", IIRC ? > > > > No strong opinion on my side as to what the behavior should be when > > XDP is disabled, but wanted to mention this so that the behavior > > change was known. > > I thought of doing this: > > diff --git a/tools/testing/selftests/drivers/net/xdp_helper.c b/tools/testing/selftests/drivers/net/xdp_helper.c > index 8f77da4f798f..8c34e8915fc4 100644 > --- a/tools/testing/selftests/drivers/net/xdp_helper.c > +++ b/tools/testing/selftests/drivers/net/xdp_helper.c > @@ -53,7 +53,7 @@ int main(int argc, char **argv) > int queue; > char byte; > > - if (argc != 3) { > + if (argc > 1 && argc != 3) { > fprintf(stderr, "Usage: %s ifindex queue_id", argv[0]); > return 1; > } > @@ -69,6 +69,13 @@ int main(int argc, char **argv) > return 1; > } > > + > + if (argc == 1) { > + printf("AF_XDP support detected\n"); > + close(sock_fd); > + return 0; > + } > + > ifindex = atoi(argv[1]); > queue = atoi(argv[2]); > > > Then we can run the helper with no arguments, just to check if af_xdp > is supported. If that returns 0 we go on, otherwise we print your nice > error. > > LMK if that sounds good, assuming a respin is needed I can add that :) That seems to fine; if you do decide to go this route in a re-spin, would you mind also adding a "\n" in the fprintf after "ifindex queue_id" ? Sorry I missed that on my initial implementation. That missing \n was mentioned by Kurt in another thread: https://lore.kernel.org/netdev/878qq22xk3.fsf@kurt.kurt.home/T/#m4d0778b9e849bc72064074105182f4c84ba55eb2 > > Separately: I retested this on a machine with XDP enabled, both with > > and without NETIF set and the test seems to hang because the helper > > is blocked on: > > > > read(STDIN_FILENO, &byte, 1); > > > > according to strace: > > > > strace: Process 14198 attached > > 21:50:02 read(0, > > > > So, I think this patch needs to be tweaked to write a byte to the > > helper so it exits (I assume before the defer was killing it?) or > > the helper needs to be modified in way? > > What Python version do you have? Python 3.12.3 (via Ubuntu 24.04.1 LTS). I can re-test with a different version using pyenv if you'd like? Are there docs which mention which python version tests should be compatible with? If so, could you pass along a link? Sorry if I missed that. > > For me the xdp process doesn't wait at all. Running this under vng > and Python 3.13 the read returns 0 immediately. Interesting, so something changed between 3.12.3 and 3.13, I suppose. > Even if it doesn't we run bkg() with default params, so exit_wait=False > init will set: > > self.terminate = not exit_wait > > and then __exit__ will do: > > return self.process(terminate=self.terminate, fail=self.check_fail) > > which does: > > if self.terminate: > self.proc.terminate() > > so the helper should get a SIGINT, no? (Minor nit, the python docs say terminate delivers a SIGTERM, but please continue reading) I'm not a python programmer but did try a bit to debug this. Looking at strace on my system, it seems that the script forks twice and the SIGTERM is sent to the wrong pid? I suppose it forks twice because the helper is invoked via /bin/sh: 18:27:15 vfork(strace: Process 448303 attached So, pid 448303 is the first forked process, which does an execve: [pid 448303] 18:27:15 execve("/bin/sh", ["/bin/sh", "-c", "/home/jdamato/code/net-next/tools/testing/selftests/drivers/net/xdp_helper 5 0"], 0x7f661511fad0 /* 26 vars */ So /bin/sh runs and that then forks again to run the helper: [pid 448278] 18:27:15 <... vfork resumed>) = 448303 [pid 448303] 18:27:15 vfork(strace: Process 448304 attached [pid 448304] 18:27:15 execve("/home/jdamato/code/net-next/tools/testing/selftests/drivers/net/xdp_helper", ["/home/jdamato/code/net-next/tools/testing/selftests/drivers/net/xdp_helper", "5", "0"], 0x55faf4f81918 /* 26 vars */ So pid 448304 is the process doing the execve to run xdp_helper and would need to be the one getting the SIGTERM/SIGINT We can see it does the read: [pid 448304] 18:27:15 read(0, However, later the python script does the terminate flow you've described in your message but sends the signal to the /bin/sh that was forked off: [pid 448278] 18:27:15 kill(448303, SIGTERM) = 0 [...] [pid 448303] 18:27:15 +++ killed by SIGTERM +++ But pid 448304 is xdp_helper, which is still running and should be the one to get the TERM. I have no idea why this would be different on your system vs mine. Maybe something changed with Python between Python versions? > We shall find out if NIPA agrees with my local system at 4p. Sorry for the noob question, but is there a NIPA url or something I can look at to see if this worked / if future tests I submit work?