** Changed in: linux (Ubuntu Bionic)
       Status: New => In Progress

** Changed in: linux (Ubuntu Cosmic)
       Status: New => In Progress

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  perf top problem on z with Ubuntu 18.04

Status in Ubuntu on IBM z Systems:
Status in linux package in Ubuntu:
  Fix Released
Status in linux source package in Bionic:
  In Progress
Status in linux source package in Cosmic:
  In Progress

Bug description:
  SRU Justification:


  * The perf top tool hangs and shows error messages, like 'Not enough
  memory for annotating'


  * edeb0c90df3581b821a764052d185df985f8b8dc edeb0c9 "perf tools: Stop
  fallbacking to kallsyms for vdso symbols lookup"

  [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 low since this happens
  only while using the perf top tool

  * and it is known that the commit (above) fixes the problem

  * and the fix is upstream since 4.19

  [Other Info]

  * current disco and eoan kernels don't show that problem

  * bisecting result points to above commit

  * applies cleanly on cosmic, but has a little conflict on bionic (both 

  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

  The level I was debugging was kernel 4.15 which does not contain this

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