Re: perf test case 40 LLVM search and compile runs endless (eBPF linkage issue)

[Jiri Olsa <olsajiri@gmail.com>]

On Mon, May 23, 2022 at 01:09:51PM +0200, Jiri Olsa wrote:
> On Mon, May 23, 2022 at 12:52:06PM +0200, Thomas Richter wrote:
> > On s390 the test case 40 'LLVM search and compile' runs for ever:
> > 
> >   # date; timeout 30s perf test -F 40; date
> >   Mon May 23 12:35:48 PM CEST 2022
> >    40: LLVM search and compile   :
> >    40.1: Basic BPF llvm compile  :
> >   Mon May 23 12:36:18 PM CEST 2022
> >   #
> > 
> > Investigation by Ilya Leoshkevich revealed:
> > On s390 we hit an endless loop where bpf_object__next_program and bpf_program__next 
> > infinitely call each other. We tracked this down to ld.so preferring the perf's 
> > bpf_object__next_program weak copy over the libbpf's strong one.
> > 
> > This is introduced with commit 2a4898fc264a ("perf tools: Add more weak libbpf functions")
> > 
> > Also see discussion in 
> > https://lore.kernel.org/lkml/YY%2FAR2Dcaws0BAE9@kernel.org/
> > 
> > How can this be fixed asap? Thanks a lot.
> 
> I was just suggesting to remove that:
>   https://lore.kernel.org/bpf/Yos8hq3NmBwemoJw@krava/T/#mda8abccbf475b99d25abe5498a5df1af2da82ee8
> 
> it's no longer needed and can cause problem apparently

after discussing with Arnaldo we decided to go for another fix,
could you please try this branch:

  git://git.kernel.org/pub/scm/linux/kernel/git/jolsa/perf.git
  perf/weak

thanks,
jirka