Re: [drm/i915/gt] 8c3b1ba0e7: perf-sanity-tests.Parse_event_definition_strings.fail

[Jiri Olsa <jolsa@redhat.com>]

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On Thu, Feb 25, 2021 at 02:33:57PM +0100, Jiri Olsa wrote:
> On Thu, Feb 25, 2021 at 04:06:23PM +0800, Jin, Yao wrote:
> > Hi Chris, Arnaldo, Jiri,
> > 
> > We observe the parsing error for "software/xxx/" on some platforms.
> > 
> > For example,
> > 
> > # perf stat -e software/r1a/ -a -- sleep 1
> > event syntax error: 'software/r1a/'
> >                      \___ parser error
> > Run 'perf list' for a list of valid events
> > 
> >  Usage: perf stat [<options>] [<command>]
> > 
> >     -e, --event <event>   event selector. use 'perf list' to list available events
> > 
> > And perf test is failed too.
> > 
> > # perf test 6 -vv
> > ...
> > running test 4 'software/r1a/'failed to parse event 'software/r1a/', err 1, str 'parser error'
> > event syntax error: 'software/r1a/'
> >                      \___ parser error
> > 
> > running test 4 'software/r0x1a/'failed to parse event 'software/r0x1a/', err 1, str 'parser error'
> > event syntax error: 'software/r0x1a/'
> >                      \___ parser error
> > ...
> > 
> > The issue should be the conflict between event "i915/software-gt-awake-time/" and pmu "software".
> > 
> > # perf list | grep i915/software
> >   i915/software-gt-awake-time/                       [Kernel PMU event]
> > 
> > Perf supports the event format as "prefix-xxx-suffix", so the "software"
> > string in "software-gt-awake-time" is added to perf_pmu_events_list as
> > PMU_EVENT_SYMBOL_PREFIX. When parsing the string such as "software/xxx/",
> > it’s parsed as PMU_EVENT_SYMBOL_PREFIX for "software", then it would error
> > out in next processing.
> > 
> > So the easy way is to rename "software-gt-awake-time" to "gt-awake-time",
> > right? Otherwise we have to hardcode something in perf tool.
> > 
> > What do you think of this issue and the solution?
> > 
> > BTW, as the robot reported, it's related to the commit 8c3b1ba0e7ea
> > ("drm/i915/gt: Track the overall awake/busy time").
> 
> yes, I think you're right.. I'll try to reproduce and check on this
> 
> I'm still not clear why is that parsing fail if those 2 events are
> distinguished by - and / ... but yep, we are asking for trouble in
> here ;-)
> 
> I think we could either prioritaze one or add extra check when we
> add prefix-xxx-suffix events and do not add ones that have conflict..
> that seems like best solution to me now

would patch below work for you?

jirka


---
diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
index 42c84adeb2fb..e1d0f1028401 100644
--- a/tools/perf/util/parse-events.c
+++ b/tools/perf/util/parse-events.c
@@ -2041,8 +2041,16 @@ static void perf_pmu__parse_init(void)
 			char *tmp = strchr(alias->name, '-');
 
 			if (tmp != NULL) {
-				SET_SYMBOL(strndup(alias->name, tmp - alias->name),
-						PMU_EVENT_SYMBOL_PREFIX);
+				char *prefix = strndup(alias->name, tmp - alias->name);
+
+				if (perf_pmu__find(prefix)) {
+					pr_debug("perf_pmu__parse_init: skipping conflicting alias '%s'\n",
+						 alias->name);
+					free(prefix);
+					continue;
+				}
+
+				SET_SYMBOL(prefix, PMU_EVENT_SYMBOL_PREFIX);
 				p++;
 				SET_SYMBOL(strdup(++tmp), PMU_EVENT_SYMBOL_SUFFIX);
 				len += 2;