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

[Pádraig Brady]

On 21/12/16 23:55, Bruno Haible wrote:
> 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

I've seen this test take a minute or so on a 40 core system.
There was a recent enough report on helgrind reporting issues with it:
https://lists.gnu.org/archive/html/bug-gnulib/2015-07/msg00032.html