perf pmus: Prefer perf_pmu__scan over perf_pmus__for_each_pmu

perf_pmus__for_each_pmu doesn't lazily initialize pmus making its use
error prone. Just use perf_pmu__scan as this only impacts
non-performance critical tests.

Reviewed-by: Kan Liang <[e-mail]>
Signed-off-by: Ian Rogers <[e-mail]>
Cc: Adrian Hunter <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: Ali Saidi <[e-mail]>
Cc: Athira Rajeev <[e-mail]>
Cc: Dmitrii Dolgov <[e-mail]>
Cc: Huacai Chen <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: James Clark <[e-mail]>
Cc: Jing Zhang <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: John Garry <[e-mail]>
Cc: Kajol Jain <[e-mail]>
Cc: Kang Minchul <[e-mail]>
Cc: Leo Yan <[e-mail]>
Cc: Madhavan Srinivasan <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: Mike Leach <[e-mail]>
Cc: Ming Wang <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Ravi Bangoria <[e-mail]>
Cc: Rob Herring <[e-mail]>
Cc: Sandipan Das <[e-mail]>
Cc: Sean Christopherson <[e-mail]>
Cc: Suzuki Poulouse <[e-mail]>
Cc: Thomas Richter <[e-mail]>
Cc: Will Deacon <[e-mail]>
Cc: Xing Zhengjun <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/bench/pmu-scan.c

···
 
 static int save_result(void)
 {
-	struct perf_pmu *pmu;
+	struct perf_pmu *pmu = NULL;
 	struct list_head *list;
 	struct pmu_scan_result *r;
 
-	perf_pmu__scan(NULL);
-
-	perf_pmus__for_each_pmu(pmu) {
+	while ((pmu = perf_pmu__scan(pmu)) != NULL) {
 		r = realloc(results, (nr_pmus + 1) * sizeof(*r));
 		if (r == NULL)
 			return -ENOMEM;

tools/perf/tests/event_groups.c

···
 
 static int setup_uncore_event(void)
 {
-	struct perf_pmu *pmu;
+	struct perf_pmu *pmu = NULL;
 	int i, fd;
 
-	if (list_empty(&pmus))
-		perf_pmu__scan(NULL);
-
-	perf_pmus__for_each_pmu(pmu) {
+	while ((pmu = perf_pmu__scan(pmu)) != NULL) {
 		for (i = 0; i < NR_UNCORE_PMUS; i++) {
 			if (!strcmp(uncore_pmus[i].name, pmu->name)) {
 				pr_debug("Using %s for uncore pmu event\n", pmu->name);

tools/perf/tests/parse-events.c

···
 	TEST_ASSERT_VAL("wrong number of entries", 0 != evlist->core.nr_entries);
 
 	perf_evlist__for_each_evsel(&evlist->core, evsel) {
-		struct perf_pmu *pmu;
+		struct perf_pmu *pmu = NULL;
 		bool type_matched = false;
 
 		TEST_ASSERT_VAL("wrong config", test_perf_config(evsel, 0x1a));
-		perf_pmus__for_each_pmu(pmu) {
+		while ((pmu = perf_pmu__scan(pmu)) != NULL) {
 			if (pmu->type == evsel->attr.type) {
 				TEST_ASSERT_VAL("PMU type expected once", !type_matched);
 				type_matched = true;
···
 
 static int test__pmu_events(struct test_suite *test __maybe_unused, int subtest __maybe_unused)
 {
-	struct perf_pmu *pmu;
+	struct perf_pmu *pmu = NULL;
 	int ret = TEST_OK;
 
-	if (list_empty(&pmus))
-		perf_pmu__scan(NULL);
-
-	perf_pmus__for_each_pmu(pmu) {
+	while ((pmu = perf_pmu__scan(pmu)) != NULL) {
 		struct stat st;
 		char path[PATH_MAX];
 		struct dirent *ent;

tools/perf/util/pmus.h

···
 extern struct list_head pmus;
 struct perf_pmu;
 
-#define perf_pmus__for_each_pmu(pmu) list_for_each_entry(pmu, &pmus, list)
-
 const struct perf_pmu *perf_pmus__pmu_for_pmu_filter(const char *str);
 
 #endif /* __PMUS_H */