linux-kernel - [PATCH v1] perf test: Parse events workaround for dash/minus

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Date:   Wed, 12 Oct 2022 18:12:05 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        John Garry <john.garry@...wei.com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        Ravi Bangoria <ravi.bangoria@....com>,
        Stephane Eranian <eranian@...gle.com>
Subject: [PATCH v1] perf test: Parse events workaround for dash/minus

Skip an event configuration for event names with a dash/minus in them.
Events with a dash/minus in their name cause parsing issues as legacy
encoding of events would use a dash/minus as a separator. The parser
separates events with dashes into prefixes and suffixes and then
recombines them. Unfortunately if an event has part of its name that
matches a legacy token then the recombining fails. This is seen for
branch-brs where branch is a legacy token. branch-brs was introduced
to sysfs in:
https://lore.kernel.org/all/20220322221517.2510440-5-eranian@google.com/
The failure is shown below as well as the workaround to use a config
where the dash/minus isn't treated specially:

```
$ perf stat -e branch-brs true
event syntax error: 'branch-brs'
                           \___ parser error

$ perf stat -e cpu/branch-brs/ true

 Performance counter stats for 'true':

            46,179      cpu/branch-brs/
```

Signed-off-by: Ian Rogers <irogers@...gle.com>
---
 tools/perf/tests/parse-events.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/tools/perf/tests/parse-events.c b/tools/perf/tests/parse-events.c
index 459afdb256a1..3440dd2616b0 100644
--- a/tools/perf/tests/parse-events.c
+++ b/tools/perf/tests/parse-events.c
@@ -2237,6 +2237,19 @@ static int test__pmu_events(struct test_suite *test __maybe_unused, int subtest
 			pr_debug("Test PMU event failed for '%s'", name);
 			ret = combine_test_results(ret, test_ret);
 		}
+		/*
+		 * Names containing '-' are recognized as prefixes and suffixes
+		 * due to '-' being a legacy PMU separator. This fails when the
+		 * prefix or suffix collides with an existing legacy token. For
+		 * example, branch-brs has a prefix (branch) that collides with
+		 * a PE_NAME_CACHE_TYPE token causing a parse error as a suffix
+		 * isn't expected after this. As event names in the config
+		 * slashes are allowed a '-' in the name we check this works
+		 * above.
+		 */
+		if (strchr(ent->d_name, '-'))
+			continue;
+
 		snprintf(name, sizeof(name), "%s:u,cpu/event=%s/u", ent->d_name, ent->d_name);
 		e.name  = name;
 		e.check = test__checkevent_pmu_events_mix;
-- 
2.38.0.rc1.362.ged0d419d3c-goog