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Two test cases have been failing on FreeBSD buildbot for a while. Let's skip the error check on FreeBSD for now.
0:27:24 load avg: 1.97 Re-running test_posix in verbose mode (matching: test_sched_getaffinity, test_sched_setaffinity)
test_sched_getaffinity (test.test_posix.PosixTester.test_sched_getaffinity) ... FAIL
test_sched_setaffinity (test.test_posix.PosixTester.test_sched_setaffinity) ... FAIL
======================================================================
FAIL: test_sched_getaffinity (test.test_posix.PosixTester.test_sched_getaffinity)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/usr/home/buildbot/python/pull_request.koobs-freebsd-564d/build/Lib/test/test_posix.py", line 1197, in test_sched_getaffinity
 self.assertRaises(OSError, posix.sched_getaffinity, -1)
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: OSError not raised by sched_getaffinity
======================================================================
FAIL: test_sched_setaffinity (test.test_posix.PosixTester.test_sched_setaffinity)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/usr/home/buildbot/python/pull_request.koobs-freebsd-564d/build/Lib/test/test_posix.py", line 1215, in test_sched_setaffinity
 self.assertRaises(OSError, posix.sched_setaffinity, -1, mask)
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: OSError not raised by sched_setaffinity
----------------------------------------------------------------------
Ran 2 tests in 0.015s

Koobs, please take a look.

FWIW, seems like the buildbot started failing at either commit cb495a1e9f3acfcd8cb94a6b89c79d0909e3383f or 708812085355c92f32e547d1f1d1f29aefbbc27e. But I have no clue how commits changing the Windows build config can lead to test_posix failing.

Koob's build bot is a FreeBSD 14 host. FreeBSD 14 is under development and has not reached stable yet. I bet that the issue was caused by a recent system and Kernel upgrade.

New changeset b82cdd1dac9a9be52051abd90a1ce69236ac41f4 by Christian Heimes in branch 'main':
bpo-47205: Skip error check of sched_get/setaffinity on FreeBSD (GH-32285)
https://github.com/python/cpython/commit/b82cdd1dac9a9be52051abd90a1ce69236ac41f4

New changeset 490ccbd6e0e5aad07a40c79a6b0c45ffca91724b by Miss Islington (bot) in branch '3.9':
bpo-47205: Skip error check of sched_get/setaffinity on FreeBSD (GH-32285)
https://github.com/python/cpython/commit/490ccbd6e0e5aad07a40c79a6b0c45ffca91724b

New changeset 470dfe20cb6e741c42c52619e122fc218e27aebd by Miss Islington (bot) in branch '3.10':
bpo-47205: Skip error check of sched_get/setaffinity on FreeBSD (GH-32285)
https://github.com/python/cpython/commit/470dfe20cb6e741c42c52619e122fc218e27aebd

Investigating

From one of our base/kernel developers:
--------------------------------------------------------------
> koobs wrote:
>
> I don't grok the system call semantics, but it appears the issue is calls
> with the '-1' argument:
>
> mask = posix.sched_getaffinity(0)
> ...
> self.assertRaises(OSError, posix.sched_getaffinity, -1)
> ...
> self.assertRaises(OSError, posix.sched_setaffinity, -1, mask)
>
> This line was added 10 years ago in:
>
> https://github.com/python/cpython/commit/848698727fcbb633246b56ab57080b4d5493c186
>
> It wants an OSError [1] and presumably was getting it before recent
> failures, but isn't anymore:
>
> [1] https://docs.python.org/3/library/exceptions.html#OSError
So this is the difference:
Python 3.11.0a6+ (heads/main:38ae5b8c0c, Apr 5 2022, 03:27:23) [GCC 11.2.0] on freebsd13
Type "help", "copyright", "credits" or "license" for more information.
>>> import posix
>>> mask = posix.sched_getaffinity(-1)
>>> mask
{0, 1, 2, 3, 4, 5, 6, 7}
Python 3.10.4 (main, Mar 25 2022, 00:00:00) [GCC 11.2.1 20220127 (Red Hat 11.2.1-9)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import posix
>>> mask = posix.sched_getaffinity(-1)
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
ProcessLookupError: [Errno 3] No such process
FreeBSD always accepted -1 as denoting the current process, while Linux
does not. In fact, Linux uses 0 as current process pid alias.
For FreeBSD, both -1 and 0 works as getpid(), and I do not see it right
to break our traditional API conventions. I believe the test should be
fixed.
--------------------------------------------------------------
I am not sure what changed between 3.10 and main that changed/removed
ProcessLookupError as the return for posix.sched_{get|set}affinity
with -1 as the argument, but that appears to be the cause of the current test failure