tdiff fails tests on 1-core VMs

[bmwiedemann]

While working on reproducible builds for openSUSE, I found that
our tdiff package randomly fails some tests when building in a 1-core VM

on openSUSE, or Debian, one can do this to reproduce:

osc checkout openSUSE:Factory/tdiff && cd $_
osc build --vm-type=kvm --noservice --clean -j1 standard

This produces random failures

 FAIL: tests/preset-alltimes.test
 FAIL: tests/preset-acl-alltimes.test
 FAIL: tests/toggle-mtime.test
 # XFAIL: 0
 # FAIL:  3

[F-i-f]

Thank you for your bug report.

I cannot reproduce the issue on a 1-core VM (running Fedora 31).
Could you send the output of the test-show-results script (in the top-level directory), ran after the tests have failed?
For example, modify your build script like this:

make && make check
./test-show-results > test-results.log

Then attach test-results.log to this issue.
Also, do you happen to know which filesystem the build is ran on?

[bmwiedemann]

tdiff.test.log.txt

It seems, the failures have a random component. Maybe something racy. The filesystem is ext4.