** Description changed:

  SRU Justification:
  ==================
  
  [Impact]
  
  * The perf top tool hangs and shows error messages, like 'Not enough
  memory for annotating'
  
  [Fix]
  
  * b9c0a64901d5bdec6eafd38d1dc8fa0e2974fccb b9c0a64 "perf annotate: Fix
  s390 gap between kernel end and module start"
  
  * 12a6d2940b5f02b4b9f71ce098e3bb02bc24a9ea 12a6d29 "perf record: Fix
  module size on s390"
  
  Disco needs also as prereq:
  
- * 6738028dd57df064b969d8392c943ef3b3ae705d 6738028 perf record: Fix s390
- missing module symbol and warning for non-root users
- 
+ * 6738028dd57df064b969d8392c943ef3b3ae705d 6738028 "perf record: Fix
+ s390 missing module symbol and warning for non-root users"
  
  [Test Case]
  
  * start a benchmark (mem_alloc, but it doesn't really matter what)
  
  * execute perf top in a second terminal
  
  * the output of perf top is correct
  
  * now stop the benchmark
  
  * and perf top shows an error message, like "Not enough memory for
  annotating '__irf_end' symbol!)"
  
  * and perf top can't be exited anymore
  
  [Regression Potential]
  
  * The regression potential can be considered as medium since this
  happens only while using the perf top tool
  
  * and just 3 files are changed, and one of them is
  arch/s390/util/machine.c
  
  * but symbol and machine header in /tools/perf/util modified and several
  loc added
  
  [Other Info]
  
  * cherry-pick was possible to bionic-master-next and to disco-master-
  next (but used '--strategy=recursive -X theirs' for disco)
  
  * adding the patches to disco is to avoid regressions
  _________________________
  
  perf top hangs and shows error messages
  
  ---uname output---
  Linux weather 4.15.0-46-generic #49-Ubuntu SMP Wed Feb 6 09:32:27 UTC 2019 
s390x s390x s390x GNU/Linux
  
  ---Steps to Reproduce---
   I start a benchmark (mem_alloc, but it really doesn't matter) and then issue 
perf top in a second terminal, the output from perf top is correct. Now I stop 
the benchmark: perf top shows a error message (Not enough memory for annotating 
'__irf_end' symbol!) and I can't quit from perf top anymore
  
  Following analyse took place:
  No problem with current kernel .
  Bi-Secting of perf tool took place and following commit was found:
  
  commit edeb0c90df3581b821a764052d185df985f8b8dc (HEAD, refs/bisect/bad)
  Author: Arnaldo Carvalho de Melo <a...@redhat.com>
  Date:   Tue Oct 16 17:08:29 2018 -0300
  
      perf tools: Stop fallbacking to kallsyms for vdso symbols lookup
  
  When you apply this patch the issue is gone, however it is contained in
  these versions:
  
  git tag --contains  edeb0c90df3581b821
  v4.19
  v4.20
  ....
  
  The level I was debugging was kernel 4.15 which does not contain this
  patch.

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https://bugs.launchpad.net/bugs/1828166

Title:
  perf top problem on z with Ubuntu 18.04

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