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

From: Thomas Richter <tmricht@linux.ibm.com>
To: "linux-perf-use." <linux-perf-users@vger.kernel.org>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Jiri Olsa <jolsa@redhat.com>,
	Sumanth Korikkar <sumanthk@linux.ibm.com>,
	Heiko Carstens <hca@linux.ibm.com>,
	vasily Gorbik <gor@linux.ibm.com>,
	Ian Rogers <irogers@google.com>,
	Ilya Leoshkevich <iii@linux.ibm.com>,
	Sven Schnelle <svens@linux.ibm.com>
Subject: perf test case 40 LLVM search and compile runs endless (eBPF linkage issue)
Date: Mon, 23 May 2022 12:52:06 +0200	[thread overview]
Message-ID: <bac4efca-c61e-5f62-daa1-f508b64d6a7f@linux.ibm.com> (raw)

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.
-- 
Thomas Richter, Dept 3303, IBM s390 Linux Development, Boeblingen, Germany
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