Re: [PATCH v1 17/23] perf pmus: Prefer perf_pmu__scan over perf_pmus__for_each_pmu

["Liang, Kan" <kan.liang@linux.intel.com>]

On 2023-05-17 10:57 a.m., Ian Rogers wrote:
> 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.
> 
> Signed-off-by: Ian Rogers <irogers@google.com>

Reviewed-by: Kan Liang <kan.liang@linux.intel.com>

Thanks,
Kan
> ---
>  tools/perf/bench/pmu-scan.c     |  6 ++----
>  tools/perf/tests/event_groups.c |  7 ++-----
>  tools/perf/tests/parse-events.c | 11 ++++-------
>  tools/perf/util/pmus.h          |  2 --
>  4 files changed, 8 insertions(+), 18 deletions(-)
> 
> diff --git a/tools/perf/bench/pmu-scan.c b/tools/perf/bench/pmu-scan.c
> index f0f007843bb8..f4a6c37cbe27 100644
> --- a/tools/perf/bench/pmu-scan.c
> +++ b/tools/perf/bench/pmu-scan.c
> @@ -40,13 +40,11 @@ static struct pmu_scan_result *results;
>  
>  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;
> diff --git a/tools/perf/tests/event_groups.c b/tools/perf/tests/event_groups.c
> index 029442b4e9c6..3d9a2b524bba 100644
> --- a/tools/perf/tests/event_groups.c
> +++ b/tools/perf/tests/event_groups.c
> @@ -50,13 +50,10 @@ static int event_open(int type, unsigned long config, int group_fd)
>  
>  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);
> diff --git a/tools/perf/tests/parse-events.c b/tools/perf/tests/parse-events.c
> index 72a10bed84fd..277607ede060 100644
> --- a/tools/perf/tests/parse-events.c
> +++ b/tools/perf/tests/parse-events.c
> @@ -108,11 +108,11 @@ static int test__checkevent_raw(struct evlist *evlist)
>  	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;
> @@ -2243,13 +2243,10 @@ static int test__terms2(struct test_suite *test __maybe_unused, int subtest __ma
>  
>  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;
> diff --git a/tools/perf/util/pmus.h b/tools/perf/util/pmus.h
> index d475e2960c10..257de10788e8 100644
> --- a/tools/perf/util/pmus.h
> +++ b/tools/perf/util/pmus.h
> @@ -5,8 +5,6 @@
>  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 */