test_timerfd_initval fails with large time difference on NetBSD

[furkanonder]

Bug report

Bug description:

The test_timerfd_initval test in test_os.TimerfdTests is failing on NetBSD with a very large time difference between the expected and actual expiration values. The test expects values to be almost equal within 3 decimal places, but the actual difference is over 1.7 billion seconds.

Configuration:

./configure --with-pydebug

Test

./python -m test test_os -m test_timerfd_initval -v

Output:

== CPython 3.14.0a6+ (heads/main:26511993e63, Mar 15 2025, 01:30:33) [GCC 10.5.0]
== NetBSD-10.0-amd64-x86_64-64bit-ELF little-endian
== Python build: debug
== cwd: /home/blue/cpython/build/test_python_worker_20567æ
== CPU count: 16
== encodings: locale=UTF-8 FS=utf-8
== resources: all test resources are disabled, use -u option to unskip tests
Using random seed: 3011250179
0:00:00 load avg: 2.25 Run 1 test sequentially in a single process
0:00:00 load avg: 2.25 [1/1] test_os
test_timerfd_initval (test.test_os.TimerfdTests.test_timerfd_initval) ... FAIL
======================================================================
FAIL: test_timerfd_initval (test.test_os.TimerfdTests.test_timerfd_initval)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/home/blue/cpython/Lib/test/test_os.py", line 4327, in test_timerfd_initval
 self.assertAlmostEqual(next_expiration, initial_expiration, places=self.CLOCK_RES_PLACES)
 ~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: 1741991497.5326333 != 0.25 within 3 places (1741991497.2826333 difference)
----------------------------------------------------------------------
Ran 1 test in 0.010s
FAILED (failures=1)
test test_os failed
0:00:00 load avg: 2.25 [1/1/1] test_os failed (1 failure)
== Tests result: FAILURE ==
1 test failed:
 test_os
Total duration: 958 ms
Total tests: run=1 (filtered) failures=1
Total test files: run=1/1 (filtered) failed=1
Result: FAILURE

OS: NetBSD-10.0-amd64

CPython versions tested on:

CPython main branch, 3.14, 3.13

Operating systems tested on:

Other

[zware]

As with gh-131263, this whole test class is supposed to be skipped on non-Linux platforms. In that framing, this could be closed as a duplicate.

[picnixz]

I think we can even close it as a duplicate of #126112

[furkanonder]

I think we can even close it as a duplicate of #126112

In addition, 3 more tests are failing. They are failing with error outputs different from those on Gentoo.

======================================================================
FAIL: test_timerfd_TFD_TIMER_ABSTIME (test.test_os.TimerfdTests.test_timerfd_TFD_TIMER_ABSTIME)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/home/blue/Desktop/cpython/Lib/test/test_os.py", line 4425, in test_timerfd_TFD_TIMER_ABSTIME
 self.assertAlmostEqual(next_expiration, offset, places=self.CLOCK_RES_PLACES)
 ~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: 1.003397717 != 1 within 3 places (0.0033977169999999113 difference)

======================================================================
FAIL: test_timerfd_initval (test.test_os.TimerfdTests.test_timerfd_initval)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/home/blue/Desktop/cpython/Lib/test/test_os.py", line 4330, in test_timerfd_initval
 self.assertAlmostEqual(next_expiration, initial_expiration, places=self.CLOCK_RES_PLACES)
 ~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: 1743795512.110591 != 0.25 within 3 places (1743795511.860591 difference)

======================================================================
FAIL: test_timerfd_ns_select (test.test_os.TimerfdTests.test_timerfd_ns_select)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/home/blue/Desktop/cpython/Lib/test/test_os.py", line 4603, in test_timerfd_ns_select
 self.assertEqual((rfd, wfd, xfd), ([], [], []))
 ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: Tuples differ: ([], [3], []) != ([], [], [])

First differing element 1:
[3]
[]

- ([], [3], [])
? -

+ ([], [], [])

======================================================================
FAIL: test_timerfd_select (test.test_os.TimerfdTests.test_timerfd_select)
----------------------------------------------------------------------
Traceback (most recent call last):
 File "/home/blue/Desktop/cpython/Lib/test/test_os.py", line 4438, in test_timerfd_select
 self.assertEqual((rfd, wfd, xfd), ([], [], []))
 ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: Tuples differ: ([], [3], []) != ([], [], [])

First differing element 1:
[3]
[]

- ([], [3], [])
? -

+ ([], [], [])

[StanFromIreland]

I think we can even close it as a duplicate of #126112

I agree, the original issue here should is resolved with #135681 The other bugs mentioned are best discussed in the other issue.

[serhiy-storchaka]

It seems that on NetBSD, timerfd_settime() returns an absolute timer value instead of relative value. Although timerfd_gettime() returns a relative timer value. I think this is a NetBSD bug. This is Linux-specific API, but NetBSD implemented it for compatibility with Linux and failed at that detail.