perf parse-events: Do not break up AUX event group

Do not assume which events may have a PMU name, allowing the logic to
keep an AUX event group together.

Example:

 Before:

    $ perf record --no-bpf-event -c 10 -e '{intel_pt//,tlb_flush.stlb_any/aux-sample-size=8192/pp}:u' -- sleep 0.1
    WARNING: events were regrouped to match PMUs
    Cannot add AUX area sampling to a group leader
    $

 After:

    $ perf record --no-bpf-event -c 10 -e '{intel_pt//,tlb_flush.stlb_any/aux-sample-size=8192/pp}:u' -- sleep 0.1
    [ perf record: Woken up 1 times to write data ]
    [ perf record: Captured and wrote 0.078 MB perf.data ]
    $ perf script -F-dso,+addr | grep -C5 tlb_flush.stlb_any | head -11
    sleep 20444 [003]  7939.510243:  1  branches:uH:  7f5350cc82a2 dl_main+0x9a2 => 7f5350cb38f0 _dl_add_to_namespace_list+0x0
    sleep 20444 [003]  7939.510243:  1  branches:uH:  7f5350cb3908 _dl_add_to_namespace_list+0x18 => 7f5350cbb080 rtld_mutex_dummy+0x0
    sleep 20444 [003]  7939.510243:  1  branches:uH:  7f5350cc8350 dl_main+0xa50 => 0 [unknown]
    sleep 20444 [003]  7939.510244:  1  branches:uH:  7f5350cc83ca dl_main+0xaca => 7f5350caeb60 _dl_process_pt_gnu_property+0x0
    sleep 20444 [003]  7939.510245:  1  branches:uH:  7f5350caeb60 _dl_process_pt_gnu_property+0x0 => 0 [unknown]
    sleep 20444  7939.510245:       10 tlb_flush.stlb_any/aux-sample-size=8192/pp: 0 7f5350caeb60 _dl_process_pt_gnu_property+0x0
    sleep 20444 [003]  7939.510254:  1  branches:uH:  7f5350cc87fe dl_main+0xefe => 7f5350ccd240 strcmp+0x0
    sleep 20444 [003]  7939.510254:  1  branches:uH:  7f5350cc8862 dl_main+0xf62 => 0 [unknown]
    sleep 20444 [003]  7939.510255:  1  branches:uH:  7f5350cc9cdc dl_main+0x23dc => 0 [unknown]
    sleep 20444 [003]  7939.510257:  1  branches:uH:  7f5350cc89f6 dl_main+0x10f6 => 7f5350cb9530 _dl_setup_hash+0x0
    sleep 20444 [003]  7939.510257:  1  branches:uH:  7f5350cc8a2d dl_main+0x112d => 7f5350cb3990 _dl_new_object+0x0
    $

Fixes: 347c2f0 ("perf parse-events: Sort and group parsed events")
Suggested-by: Ian Rogers <[email protected]>
Signed-off-by: Adrian Hunter <[email protected]>
Tested-by: Ian Rogers <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Namhyung Kim <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

Author: ahunter6

tools/perf/util/evsel.c

@@ -829,11 +829,9 @@ bool evsel__name_is(struct evsel *evsel, const char *name)
 
 const char *evsel__group_pmu_name(const struct evsel *evsel)
 {
-	struct evsel *leader, *pos;
+	struct evsel *leader = evsel__leader(evsel);
+	struct evsel *pos;
 
-	/* If the pmu_name is set use it. pmu_name isn't set for CPU and software events. */
-	if (evsel->pmu_name)
-		return evsel->pmu_name;
 	/*
 	 * Software events may be in a group with other uncore PMU events. Use
 	 * the pmu_name of the first non-software event to avoid breaking the
@@ -842,7 +840,6 @@ const char *evsel__group_pmu_name(const struct evsel *evsel)
 	 * Aux event leaders, like intel_pt, expect a group with events from
 	 * other PMUs, so substitute the AUX event's PMU in this case.
 	 */
-	leader  = evsel__leader(evsel);
 	if (evsel->core.attr.type == PERF_TYPE_SOFTWARE || evsel__is_aux_event(leader)) {
 		/* Starting with the leader, find the first event with a named PMU. */
 		for_each_group_evsel(pos, leader) {
@@ -851,7 +848,7 @@ const char *evsel__group_pmu_name(const struct evsel *evsel)
 		}
 	}
 
-	return "cpu";
+	return evsel->pmu_name ?: "cpu";
 }
 
 const char *evsel__metric_id(const struct evsel *evsel)