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: a9a17902 ("perf stat: Ensure group is defined on top of the same cpu mask")
Signed-off-by: NKan Liang <kan.liang@linux.intel.com>
Acked-by: NIan Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Xing Zhengjun <zhengjun.xing@linux.intel.com>
Link: https://lore.kernel.org/r/20220518143900.1493980-3-kan.liang@linux.intel.comSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-stat.c

@@ -272,11 +272,8 @@ static void evlist__check_cpu_maps(struct evlist *evlist)
 			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

@@ -1747,11 +1747,7 @@ struct evsel *evlist__reset_weak_group(struct evlist *evsel_list, struct evsel *
 			 * 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

@@ -3109,7 +3109,16 @@ bool __weak arch_evsel__must_be_in_group(const struct evsel *evsel __maybe_unuse
 	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

@@ -499,7 +499,7 @@ bool evsel__has_leader(struct evsel *evsel, struct evsel *leader);
 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);