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

[Jiri Olsa <jolsa@redhat.com>]

On Thu, Feb 25, 2021 at 07:50:46PM +0100, Jiri Olsa wrote:
> On Thu, Feb 25, 2021 at 07:16:44PM +0100, Jiri Olsa wrote:
> > 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
> 
> and now with more fixes after I ran tests ;-)
> 
> we should perhaps add also same check for non '-' aliases, I'll check

and one more version ;-)

jirka


---
diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
index 42c84adeb2fb..d9e795056d15 100644
--- a/tools/perf/util/parse-events.c
+++ b/tools/perf/util/parse-events.c
@@ -2028,30 +2028,49 @@ static void perf_pmu__parse_init(void)
 		perf_pmu_events_list_num = -1;
 		return;
 	}
-	perf_pmu_events_list = malloc(sizeof(struct perf_pmu_event_symbol) * len);
+	perf_pmu_events_list = zalloc(sizeof(struct perf_pmu_event_symbol) * len);
 	if (!perf_pmu_events_list)
 		return;
-	perf_pmu_events_list_num = len;
 
 	len = 0;
 	pmu = NULL;
 	while ((pmu = perf_pmu__scan(pmu)) != NULL) {
 		list_for_each_entry(alias, &pmu->aliases, list) {
 			struct perf_pmu_event_symbol *p = perf_pmu_events_list + len;
-			char *tmp = strchr(alias->name, '-');
+			char *prefix = strdup(alias->name);
+			char *tmp = strchr(prefix, '-');
+
+			if (tmp != NULL)
+				*tmp = 0;
+
+			/*
+			 * Skip any prefix that conflicts with pmu name,
+			 * otherwise the event parser gets confused.
+			 */
+			if (perf_pmu__find(prefix)) {
+				pr_debug2("perf_pmu__parse_init: skipping conflicting alias '%s'\n",
+					  alias->name);
+				free(prefix);
+				continue;
+			}
 
 			if (tmp != NULL) {
-				SET_SYMBOL(strndup(alias->name, tmp - alias->name),
-						PMU_EVENT_SYMBOL_PREFIX);
+				SET_SYMBOL(prefix, PMU_EVENT_SYMBOL_PREFIX);
 				p++;
 				SET_SYMBOL(strdup(++tmp), PMU_EVENT_SYMBOL_SUFFIX);
 				len += 2;
 			} else {
-				SET_SYMBOL(strdup(alias->name), PMU_EVENT_SYMBOL);
+				SET_SYMBOL(prefix, PMU_EVENT_SYMBOL);
 				len++;
 			}
 		}
 	}
+
+	/* unlikely, but still.. */
+	if (!len)
+		goto err;
+	perf_pmu_events_list_num = len;
+
 	qsort(perf_pmu_events_list, len,
 		sizeof(struct perf_pmu_event_symbol), comp_pmu);