perf stat: Always keep perf metrics topdown events in a group

If any member in a group has a different cpu mask than the other
members, the current perf stat disables group. when the perf metrics
topdown events are part of the group, the below <not supported> error
will be triggered.

$ perf stat -e "{slots,topdown-retiring,uncore_imc_free_running_0/dclk/}" -a sleep 1
WARNING: grouped events cpus do not match, disabling group:
anon group { slots, topdown-retiring, uncore_imc_free_running_0/dclk/ }

Performance counter stats for 'system wide':

141,465,174 slots
<not supported> topdown-retiring
1,605,330,334 uncore_imc_free_running_0/dclk/

The perf metrics topdown events must always be grouped with a slots
event as leader.

Factor out evsel__remove_from_group() to only remove the regular events
from the group.

Remove evsel__must_be_in_group(), since no one use it anymore.

With the patch, the topdown events aren't broken from the group for the
splitting.

$ perf stat -e "{slots,topdown-retiring,uncore_imc_free_running_0/dclk/}" -a sleep 1
WARNING: grouped events cpus do not match, disabling group:
anon group { slots, topdown-retiring, uncore_imc_free_running_0/dclk/ }

Performance counter stats for 'system wide':

346,110,588 slots
124,608,256 topdown-retiring
1,606,869,976 uncore_imc_free_running_0/dclk/

1.003877592 seconds time elapsed

Fixes: a9a1790247bdcf3b ("perf stat: Ensure group is defined on top of the same cpu mask")
Signed-off-by: Kan Liang <[e-mail]>
Acked-by: Ian Rogers <[e-mail]>
Cc: Adrian Hunter <[e-mail]>
Cc: Andi Kleen <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Stephane Eranian <[e-mail]>
Cc: Xing Zhengjun <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/builtin-stat.c

···
 			pr_warning("     %s: %s\n", evsel->name, buf);
 		}
 
-		for_each_group_evsel(pos, leader) {
-			evsel__set_leader(pos, pos);
-			pos->core.nr_members = 0;
-		}
-		evsel->core.leader->nr_members = 0;
+		for_each_group_evsel(pos, leader)
+			evsel__remove_from_group(pos, leader);
 	}
 }
 

tools/perf/util/evlist.c

···
 			 * them. Some events, like Intel topdown, require being
 			 * in a group and so keep these in the group.
 			 */
-			if (!evsel__must_be_in_group(c2) && c2 != leader) {
-				evsel__set_leader(c2, c2);
-				c2->core.nr_members = 0;
-				leader->core.nr_members--;
-			}
+			evsel__remove_from_group(c2, leader);
 
 			/*
 			 * Set this for all former members of the group

tools/perf/util/evsel.c

···
 	return false;
 }
 
-bool evsel__must_be_in_group(const struct evsel *evsel)
+/*
+ * Remove an event from a given group (leader).
+ * Some events, e.g., perf metrics Topdown events,
+ * must always be grouped. Ignore the events.
+ */
+void evsel__remove_from_group(struct evsel *evsel, struct evsel *leader)
 {
-	return arch_evsel__must_be_in_group(evsel);
+	if (!arch_evsel__must_be_in_group(evsel) && evsel != leader) {
+		evsel__set_leader(evsel, evsel);
+		evsel->core.nr_members = 0;
+		leader->core.nr_members--;
+	}
 }

tools/perf/util/evsel.h

···
 bool evsel__is_leader(struct evsel *evsel);
 void evsel__set_leader(struct evsel *evsel, struct evsel *leader);
 int evsel__source_count(const struct evsel *evsel);
-bool evsel__must_be_in_group(const struct evsel *evsel);
+void evsel__remove_from_group(struct evsel *evsel, struct evsel *leader);
 
 bool arch_evsel__must_be_in_group(const struct evsel *evsel);