perf parse-events: When fixing group leaders always set the leader

The evsel grouping fix iterates over evsels tracking the leader group
and the current position's group, updating the current position's leader
if an evsel is being forced into a group or groups changed. However,
groups changing isn't a sufficient condition as sorting may have
reordered events and the leader may no longer come first. For this
reason update all leaders whenever they disagree.

This change breaks certain Icelake+ metrics due to bugs in the
kernel. For example, tma_l3_bound with threshold enabled tries to
program the events:

  {topdown-retiring,slots,CYCLE_ACTIVITY.STALLS_L2_MISS,topdown-fe-bound,EXE_ACTIVITY.BOUND_ON_STORES,EXE_ACTIVITY.1_PORTS_UTIL,topdown-be-bound,cpu/INT_MISC.RECOVERY_CYCLES,cmask=1,edge/,CYCLE_ACTIVITY.STALLS_L3_MISS,CPU_CLK_UNHALTED.THREAD,CYCLE_ACTIVITY.STALLS_MEM_ANY,EXE_ACTIVITY.2_PORTS_UTIL,CYCLE_ACTIVITY.STALLS_TOTAL,topdown-bad-spec}:W

fixing the perf metric event order gives:

  {slots,topdown-retiring,topdown-fe-bound,topdown-be-bound,topdown-bad-spec,CYCLE_ACTIVITY.STALLS_L2_MISS,EXE_ACTIVITY.BOUND_ON_STORES,EXE_ACTIVITY.1_PORTS_UTIL,cpu/INT_MISC.RECOVERY_CYCLES,cmask=1,edge/,CYCLE_ACTIVITY.STALLS_L3_MISS,CPU_CLK_UNHALTED.THREAD,CYCLE_ACTIVITY.STALLS_MEM_ANY,EXE_ACTIVITY.2_PORTS_UTIL,CYCLE_ACTIVITY.STALLS_TOTAL}:W

Both of these return "<not counted>" for all events, whilst they work
with the group removed respecting that the perf metric events must still
be grouped. A vendor events update will need to add METRIC_NO_GROUP to
these metrics to workaround the kernel PMU driver issue.

Fixes: a90cc5a9 ("perf evsel: Don't let evsel__group_pmu_name() traverse unsorted group")
Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: Andi Kleen <ak@linux.intel.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Xing Zhengjun <zhengjun.xing@linux.intel.com>
Link: https://lore.kernel.org/r/20230719001836.198363-3-irogers@google.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/parse-events.c

@@ -2189,7 +2189,7 @@ static int parse_events__sort_events_and_fix_groups(struct list_head *list)
 	list_for_each_entry(pos, list, core.node) {
 		const struct evsel *pos_leader = evsel__leader(pos);
 		const char *pos_pmu_name = pos->group_pmu_name;
-		const char *cur_leader_pmu_name, *pos_leader_pmu_name;
+		const char *cur_leader_pmu_name;
 		bool pos_force_grouped = arch_evsel__must_be_in_group(pos);
 
 		/* Reset index and nr_members. */
@@ -2223,13 +2223,8 @@ static int parse_events__sort_events_and_fix_groups(struct list_head *list)
 			 */
 			cur_leader_force_grouped = pos_force_grouped;
 		}
-		pos_leader_pmu_name = pos_leader->group_pmu_name;
-		if (strcmp(pos_leader_pmu_name, pos_pmu_name) || pos_force_grouped) {
-			/*
-			 * Event's PMU differs from its leader's. Groups can't
-			 * span PMUs, so update leader from the group/PMU
-			 * tracker.
-			 */
+		if (pos_leader != cur_leader) {
+			/* The leader changed so update it. */
 			evsel__set_leader(pos, cur_leader);
 		}
 	}