Re: Test-lock hang (not 100% reproducible) on GNU/Linux

[Bruno Haible]

Hi Pavel,

> But I'm rather asking whether we know about recent issues.
> 
> Firstly I noticed the hang on ppc64le, but later it occurred on x86_64, ppc64
> and i686: https://koji.fedoraproject.org/koji/taskinfo?taskID=16970779
> so this is not arch-specific issue.

I can find these (old) reports:
* "On machines with massive amounts of CPUs, the gnulib 'test-lock'
   could take minutes, or even appear to deadlock, because of timing
   interactions between multiple cores." [1]
* "I believe this is a bug in the futex code due to a missing barrier." [2]
* A hang on FreeBSD, unknown cause [3]

You should try to let it run for 10 minutes, in the first place. I think
its total running time depends on whether the thread scheduler in the kernel
is fair or not.

Bruno

[1] https://www.redhat.com/archives/libvir-list/2012-March/msg00854.html
[2] https://bugzilla.redhat.com/show_bug.cgi?id=1155291
[3] https://lists.gnu.org/archive/html/bug-gnulib/2014-09/msg00025.html