perf test case 6 dumps core on s390 without PMU

[Thomas Richter <tmricht@linux.ibm.com>]

Using Linux 6.5.0rc3 perf test case 6 dumps core on an s390 without
configured PMU (this can happen depending on customer machine configuration).

In this configuration several perf test cases fail:
 # ./perf test 2>&1 | grep FAIL
  6.1: Test event parsing                                : FAILED!
 10.3: Parsing of PMU event table metrics                : FAILED!
 10.4: Parsing of PMU event table metrics with fake PMUs : FAILED!
 28: Use a dummy software event to keep tracking         : FAILED!
 35: Track with sched_switch                             : FAILED!
 66: Parse and process metrics                           : FAILED!
 #

Even worse the test case 6 dumps core:

 # ./perf test -F 6
  6: Parse event definition strings                      :
  6.1: Test event parsing                                :
 Segmentation fault (core dumped)
 #

The root cause for these failures and core dump is a missing
PMU, as can be seen by the debug output:
   ...
   Event test failure: test 57 'instructions:uep'
   running test 58 '{cycles,cache-misses,branch-misses}:e'
   No PMU found for 'cycles' <-- Here no PMU is found, because there is none!
   FAILED tests/parse-events.c:1516 wrong number of entries
   Event test failure: test 58 '{cycles,cache-misses,branch-misses}:e'
Here no PMU is found, because there is none!

   ....
   running test 59 'cycles/name=name/'
   No PMU found for 'name'
   Segmentation fault (core dumped)

Here the root cause in in function test__term_equal_term() variable
evsel->name is NULL:

 # gdb ./perf
....
Breakpoint 1, test__term_equal_term (evlist=0x1542c00) at\
                       tests/parse-events.c:1688
(gdb) p evsel->name
$3 = 0x3fff7fe3dc0 ""
(gdb) n
 691 TEST_ASSERT_VAL("wrong type", evsel->core.attr.type == PERF_TYPE_HARDWARE);
(gdb) n
1692 TEST_ASSERT_VAL("wrong config", test_config(evsel, PERF_COUNT_HW_CPU_CYCLES));
(gdb) n
1693 TEST_ASSERT_VAL("wrong name setting", strcmp(evsel->name, "name") == 0);
(gdb) n

Program received signal SIGSEGV, Segmentation fault.

I could fix this by checking for NULL pointer, but I have the
feeling that there is more to it. However I do not fully understand
the latest rework on the event handling.

The other test cases listed above fail due to the same root cause,
no PMU found.

Please advise. What should all these test return when a system does
not have any PMU defined at all?

Thanks a lot.

-- 
Thomas Richter, Dept 3303, IBM s390 Linux Development, Boeblingen, Germany
--
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Geschäftsführung: David Faller
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