perf test attr: Fix python error on empty result

Commit-ID:  3440fe2790aa3d13530260af6033533b18959aee
Gitweb:     https://git.kernel.org/tip/3440fe2790aa3d13530260af6033533b18959aee
Author:     Thomas Richter <[email protected]>
AuthorDate: Wed, 13 Sep 2017 10:12:08 +0200
Committer:  Arnaldo Carvalho de Melo <[email protected]>
CommitDate: Mon, 2 Oct 2017 14:00:20 -0300

perf test attr: Fix python error on empty result

Commit d78ada4a767 ("perf tests attr: Do not store failed events") does not create an event file in the /tmp directory when the perf_open_event() system call failed.

This can lead to a situation where not /tmp/event-xx-yy-zz result file exists at all (for example on a s390x virtual machine environment) where no CPUMF hardware is available.

The following command then fails with a python call back chain instead of printing failure:

[root@s8360046 perf]# /usr/bin/python2 ./tests/attr.py -d ./tests/attr/ \
-p ./perf -v -ttest-stat-basic
running './tests/attr//test-stat-basic'
Traceback (most recent call last):

    File "./tests/attr.py", line 379, in <module>
      main()
    File "./tests/attr.py", line 370, in main
      run_tests(options)
    File "./tests/attr.py", line 311, in run_tests
      Test(f, options).run()
    File "./tests/attr.py", line 300, in run
      self.compare(self.expect, self.result)
    File "./tests/attr.py", line 248, in compare
      exp_event.diff(res_event)

UnboundLocalError: local variable 'res_event' referenced before assignment [root@s8360046 perf]#

This patch catches this pitfall and prints an error message instead:

  [root@s8360047 perf]# /usr/bin/python2 ./tests/attr.py -d ./tests/attr/ \
       -p ./perf  -vvv -ttest-stat-basic
  running './tests/attr//test-stat-basic'
    loading expected events
      Event event:base-stat
        fd = 1
        group_fd = -1
        flags = 0|8
        [....]
        sample_regs_user = 0
        sample_stack_user = 0
    'PERF_TEST_ATTR=/tmp/tmpJbMQMP ./perf stat -o /tmp/tmpJbMQMP/perf.data -e cycles kill >/dev/null 2>&1' ret '1', expected '1'
    loading result events
    compare
      matching [event:base-stat]
      match: [event:base-stat] matches []
      res_event is empty
  FAILED './tests/attr//test-stat-basic' - match failure
  [root@s8360047 perf]#

LPU-Reference: [email protected]

---
 tools/perf/tests/attr.py | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

index 6bb50e8..a13cd78 100644
@@ -237,6 +237,7 @@ class Test(object):
         # events in result. Fail if there's not any.
         for exp_name, exp_event in expect.items():
             exp_list = []
+            res_event = {}
             log.debug("    matching [%s]" % exp_name)
             for res_name, res_event in result.items():
                 log.debug("      to [%s]" % res_name)

@@ -253,7 +254,10 @@ class Test(object):
                 if exp_event.optional():
                     log.debug("    %s does not match, but is optional" % exp_name)
                 else:
-                    exp_event.diff(res_event)
+                    if not res_event:
+                        log.debug("    res_event is empty");
+                    else:
+                        exp_event.diff(res_event)
                     raise Fail(self, 'match failure');
 
             match[exp_name] = exp_list