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Subject[tip:perf/core] perf test attr: Fix python error on empty result
Commit-ID:  3440fe2790aa3d13530260af6033533b18959aee
Author: Thomas Richter <>
AuthorDate: Wed, 13 Sep 2017 10:12:08 +0200
Committer: Arnaldo Carvalho de Melo <>
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/ -d ./tests/attr/ \
-p ./perf -v -ttest-stat-basic
running './tests/attr//test-stat-basic'
Traceback (most recent call last):
File "./tests/", line 379, in <module>
File "./tests/", line 370, in main
File "./tests/", line 311, in run_tests
Test(f, options).run()
File "./tests/", line 300, in run, self.result)
File "./tests/", line 248, in compare
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/ -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/ -e cycles kill >/dev/null 2>&1' ret '1', expected '1'
loading result events
matching [event:base-stat]
match: [event:base-stat] matches []
res_event is empty
FAILED './tests/attr//test-stat-basic' - match failure
[root@s8360047 perf]#

Signed-off-by: Thomas-Mich Richter <>
Acked-by: Jiri Olsa <>
Cc: Heiko Carstens <>
Cc: Hendrik Brueckner <>
Cc: Martin Schwidefsky <>
Cc: Thomas-Mich Richter <>
Signed-off-by: Arnaldo Carvalho de Melo <>
tools/perf/tests/ | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/tools/perf/tests/ b/tools/perf/tests/
index 6bb50e8..a13cd78 100644
--- a/tools/perf/tests/
+++ b/tools/perf/tests/
@@ -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)
- 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
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