Re: Intermittent t_timerfd failures

[Andreas Gustafsson <gson%NetBSD.org@localhost>]

Taylor R Campbell wrote:
> sys/lib/libc/sys/t_timerfd.c timerfd_block is intermittently failing
> on the i386 test bed.

Here are some random observations from grepping the logs on various
testbeds.

1. The failures have been happening for as long as the timerfd test
case has existed.  The test case was first run with source date
2021.09.19.15.52.55, and the first failure was soon thereafter,
using source date 2021.09.21.09.24.15.

2. The execution time recorded by ATF on i386 indicates that the
failed test cases completed in less than a second, while the
successful ones took longer.  For example:

2023/2023.07.08.15.32.58/test.log.gz:    timerfd_block: [1.211653s] Passed.
2023/2023.07.08.16.13.00/test.log.gz:    timerfd_block: [1.540414s] Passed.
2023/2023.07.08.17.43.13/test.log.gz:    timerfd_block: [1.649699s] Passed.
2023/2023.07.08.19.10.00/test.log.gz:    timerfd_block: [0.864084s] Failed: /tmp/build/2023.07.08.19.10.00-i386/src/tests/lib/libc/sys/t_timerfd.c:198: then=1368.605876566 now=1369.462708087 delta=0.856831521
2023/2023.07.08.20.02.10/test.log.gz:    timerfd_block: [1.203076s] Passed.
2023/2023.07.08.23.42.48/test.log.gz:    timerfd_block: [1.699977s] Passed.
2023/2023.07.09.00.01.55/test.log.gz:    timerfd_block: [1.231773s] Passed.

3. The TNF amd64 testbed shows failures similar to the i386 one.
Both are using "qemu -accel kvm" hosted on NetBSD 9.

4. The TNF sparc testbed shows no failures in 3456 runs (using
plain qemu, no acceleration).

5. The TNF macppc testbed (also plain qemu) shows frequent failures,
but unlike i386 and amd64, the execution time indicated by ATF is more
than a second:

./2023/2023.07.06.07.59.00/test.log.gz:    timerfd_block: [1.132080s] Passed.
./2023/2023.07.07.00.20.39/test.log.gz:    timerfd_block: [1.062924s] Passed.
./2023/2023.07.07.04.43.15/test.log.gz:    timerfd_block: [1.029156s] Failed: /tmp/build/2023.07.07.04.43.15-macppc/src/tests/lib/libc/sys/t_timerfd.c:198: check_value_against_bounds(delta.tv_sec, 1, 1) not met
./2023/2023.07.07.08.39.23/test.log.gz:    timerfd_block: [1.056571s] Passed.
./2023/2023.07.07.20.19.08/test.log.gz:    timerfd_block: [1.081552s] Passed.

6. My own amd64 testbed running on real hardware shows no failures in
205 runs.

7. My own i386 testbed using "qemu -accel kvm" on Linux shows no
failures in 359 runs.
-- 
Andreas Gustafsson, gson%NetBSD.org@localhost