perf python: Improve leader copying from evlist

JIRA: https://issues.redhat.com/browse/RHEL-78198

upstream
========
commit 421c5f3
Author: Ian Rogers <irogers@google.com>
Date: Thu Jul 10 16:51:25 2025 -0700

description
===========
The struct pyrf_evlist embeds the evlist requiring the copying from
things like parsed events. The copying logic handles the leader being
the event itself, but if the leader group event is a different in the
list it will cause an evsel to point to the evsel in the list that was
copied from which is bad. Fix this by adding another pass over the
evlist rewriting leaders, simplified by the introductin of two evlist
helpers.

    Signed-off-by: Ian Rogers <irogers@google.com>
    Link: https://lore.kernel.org/r/20250710235126.1086011-13-irogers@google.com
    Signed-off-by: Namhyung Kim <namhyung@kernel.org>

Signed-off-by: Michael Petlan <mpetlan@redhat.com>

Author: rfmvh

tools/perf/util/python.c

@@ -1568,10 +1568,37 @@ static PyObject *pyrf_evsel__from_evsel(struct evsel *evsel)
 	return (PyObject *)pevsel;
 }
 
+static int evlist__pos(struct evlist *evlist, struct evsel *evsel)
+{
+	struct evsel *pos;
+	int idx = 0;
+
+	evlist__for_each_entry(evlist, pos) {
+		if (evsel == pos)
+			return idx;
+		idx++;
+	}
+	return -1;
+}
+
+static struct evsel *evlist__at(struct evlist *evlist, int idx)
+{
+	struct evsel *pos;
+	int idx2 = 0;
+
+	evlist__for_each_entry(evlist, pos) {
+		if (idx == idx2)
+			return pos;
+		idx2++;
+	}
+	return NULL;
+}
+
 static PyObject *pyrf_evlist__from_evlist(struct evlist *evlist)
 {
 	struct pyrf_evlist *pevlist = PyObject_New(struct pyrf_evlist, &pyrf_evlist__type);
 	struct evsel *pos;
+	struct rb_node *node;
 
 	if (!pevlist)
 		return NULL;
@@ -1583,9 +1610,39 @@ static PyObject *pyrf_evlist__from_evlist(struct evlist *evlist)
 
 		evlist__add(&pevlist->evlist, &pevsel->evsel);
 	}
+	evlist__for_each_entry(&pevlist->evlist, pos) {
+		struct evsel *leader = evsel__leader(pos);
+
+		if (pos != leader) {
+			int idx = evlist__pos(evlist, leader);
+
+			if (idx >= 0)
+				evsel__set_leader(pos, evlist__at(&pevlist->evlist, idx));
+			else if (leader == NULL)
+				evsel__set_leader(pos, pos);
+		}
+	}
 	metricgroup__copy_metric_events(&pevlist->evlist, /*cgrp=*/NULL,
 					&pevlist->evlist.metric_events,
 					&evlist->metric_events);
+	for (node = rb_first_cached(&pevlist->evlist.metric_events.entries); node;
+	     node = rb_next(node)) {
+		struct metric_event *me = container_of(node, struct metric_event, nd);
+		struct list_head *mpos;
+		int idx = evlist__pos(evlist, me->evsel);
+
+		if (idx >= 0)
+			me->evsel = evlist__at(&pevlist->evlist, idx);
+		list_for_each(mpos, &me->head) {
+			struct metric_expr *e = container_of(mpos, struct metric_expr, nd);
+
+			for (int j = 0; e->metric_events[j]; j++) {
+				idx = evlist__pos(evlist, e->metric_events[j]);
+				if (idx >= 0)
+					e->metric_events[j] = evlist__at(&pevlist->evlist, idx);
+			}
+		}
+	}
 	return (PyObject *)pevlist;
 }