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Date: Tue, 8 Aug 2023 10:53:36 +0200
From: Mirsad Todorovac <mirsad.todorovac@....unizg.hr>
To: Kuniyuki Iwashima <kuniyu@...zon.com>
Cc: alexander@...alicyn.com, davem@...emloft.net, edumazet@...gle.com,
fw@...len.de, kuba@...nel.org, linux-kernel@...r.kernel.org,
linux-kselftest@...r.kernel.org, netdev@...r.kernel.org,
pabeni@...hat.com, shuah@...nel.org
Subject: Re: selftests: net/af_unix test_unix_oob [FAILED]
On 8/8/23 01:09, Mirsad Todorovac wrote:
> On 8/7/23 22:46, Kuniyuki Iwashima wrote:
>> From: Mirsad Todorovac <mirsad.todorovac@....unizg.hr>
>> Date: Mon, 7 Aug 2023 21:44:41 +0200
>>> Hi all,
>>>
>>> In the kernel 6.5-rc5 build on Ubuntu 22.04 LTS (jammy jellyfish) on a Ryzen 7950 assembled box,
>>> vanilla torvalds tree kernel, the test test_unix_oob unexpectedly fails:
>>>
>>> # selftests: net/af_unix: test_unix_oob
>>> # Test 2 failed, sigurg 23 len 63 OOB %
>>>
>>> It is this code:
>>>
>>> /* Test 2:
>>> * Verify that the first OOB is over written by
>>> * the 2nd one and the first OOB is returned as
>>> * part of the read, and sigurg is received.
>>> */
>>> wait_for_data(pfd, POLLIN | POLLPRI);
>>> len = 0;
>>> while (len < 70)
>>> len = recv(pfd, buf, 1024, MSG_PEEK);
>>> len = read_data(pfd, buf, 1024);
>>> read_oob(pfd, &oob);
>>> if (!signal_recvd || len != 127 || oob != '#') {
>>> fprintf(stderr, "Test 2 failed, sigurg %d len %d OOB %c\n",
>>> signal_recvd, len, oob);
>>> die(1);
>>> }
>>>
>>> In 6.5-rc4, this test was OK, so it might mean we have a regression?
>>
>> Thanks for reporting.
>>
>> I confirmed the test doesn't fail on net-next at least, but it's based
>> on v6.5-rc4.
>>
>> ---8<---
>> [root@...alhost ~]# ./test_unix_oob
>> [root@...alhost ~]# echo $?
>> 0
>> [root@...alhost ~]# uname -r
>> 6.5.0-rc4-01192-g66244337512f
>> ---8<---
>>
>> I'll check 6.5-rc5 later.
>
> Hi, Kuniyuki,
>
> It seems that there is a new development. I could reproduce the error with the failed test 2
> as early as 6.0-rc1. However, the gotcha is that the error appears to be sporadically manifested
> (possibly a race)?
>
> I am currently attempting a bisect.
Bisect had shown that the condition existed already at 5.11 torvalds tree.
It has to do with the configs chosen (I used the configs from seltests/*/config merged), but it
is also present in the Ubuntu production build:
marvin@...iant:~$ cd linux/kernel/linux_torvalds
marvin@...iant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
marvin@...iant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
marvin@...iant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
marvin@...iant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
marvin@...iant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
Test 2 failed, sigurg 23 len 63 OOB %
marvin@...iant:~/linux/kernel/linux_torvalds$ uname -rms
Linux 6.4.8-060408-generic x86_64
marvin@...iant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
marvin@...iant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
marvin@...iant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
marvin@...iant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
marvin@...iant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
marvin@...iant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
marvin@...iant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
marvin@...iant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
marvin@...iant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
marvin@...iant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
marvin@...iant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
marvin@...iant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
marvin@...iant:~/linux/kernel/linux_torvalds$ for a in {0..1000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
Test 1 failed sigurg 0 len 63
marvin@...iant:~/linux/kernel/linux_torvalds$
It happens on rare occasions, so it seems to be a hard-to-spot race.
Normal test running test_unix_oob once never noticed that, save by accident, which brought the problem to attention ...
However, the problem seems to be config-driven rather than kernel-version-driven.
marvin@...iant:~/linux/kernel/linux_torvalds$ for a in {0..100000}; do tools/testing/selftests/net/af_unix/test_unix_oob ; done
Test 3.1 Inline failed, len 1 oob % atmark 0
Test 1 Inline failed, sigurg 0 len 63
Test 1 Inline failed, sigurg 0 len 63
Test 1 Inline failed, sigurg 0 len 63
Test 2 Inline failed, len 63 atmark 1
Test 3 Inline failed, sigurg 23 len 63 data x
Test 3 Inline failed, sigurg 23 len 63 data x
Test 3 Inline failed, sigurg 23 len 63 data x
Test 3 Inline failed, sigurg 23 len 63 data x
Test 2 Inline failed, len 63 atmark 1
Test 3.1 Inline failed, len 1 oob % atmark 0
Test 2 failed, sigurg 23 len 63 OOB %
marvin@...iant:~/linux/kernel/linux_torvalds$ uname -rms
Linux 6.5.0-060500rc4-generic x86_64
marvin@...iant:~/linux/kernel/linux_torvalds$
At moments, I was able to reproduce with certain configs, but now something odd happens.
I will keep investigating.
Kind regards,
Mirsad
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