perf pmus: Add notion of default PMU for JSON events

JSON events created in pmu-events.c by jevents.py may not specify a
PMU they are associated with, in which case it is implied that it is
the first core PMU. Care is needed to select this for regular 'cpu',
s390 'cpum_cf' and ARMs many names as at the point the name is first
needed the core PMUs list hasn't been initialized. Add a helper in
perf_pmus to create this value, in the worst case by scanning sysfs.

v2. Add missing close if fdopendir fails.

Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: Thomas Richter <tmricht@linux.ibm.com>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: James Clark <james.clark@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Thomas Richter <tmricht@linux.ibm.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Link: https://lore.kernel.org/r/20230623043843.4080180-1-irogers@google.com
Signed-off-by: Namhyung Kim <namhyung@kernel.org>

1 files changed, 36 insertions, 1 deletions

diff --git a/tools/perf/util/pmus.c b/tools/perf/util/pmus.c
index d891d72c824e..0866dee3fc62 100644
--- a/tools/perf/util/pmus.c
+++ b/tools/perf/util/pmus.c
@@ -137,8 +137,10 @@ static void pmu_read_sysfs(bool core_only)
 		return;
 
 	dir = fdopendir(fd);
-	if (!dir)
+	if (!dir) {
+		close(fd);
 		return;
+	}
 
 	while ((dent = readdir(dir))) {
 		if (!strcmp(dent->d_name, ".") || !strcmp(dent->d_name, ".."))
@@ -524,6 +526,39 @@ bool perf_pmus__supports_extended_type(void)
 	return perf_pmus__do_support_extended_type;
 }
 
+char *perf_pmus__default_pmu_name(void)
+{
+	int fd;
+	DIR *dir;
+	struct dirent *dent;
+	char *result = NULL;
+
+	if (!list_empty(&core_pmus))
+		return strdup(list_first_entry(&core_pmus, struct perf_pmu, list)->name);
+
+	fd = perf_pmu__event_source_devices_fd();
+	if (fd < 0)
+		return strdup("cpu");
+
+	dir = fdopendir(fd);
+	if (!dir) {
+		close(fd);
+		return strdup("cpu");
+	}
+
+	while ((dent = readdir(dir))) {
+		if (!strcmp(dent->d_name, ".") || !strcmp(dent->d_name, ".."))
+			continue;
+		if (is_pmu_core(dent->d_name)) {
+			result = strdup(dent->d_name);
+			break;
+		}
+	}
+
+	closedir(dir);
+	return result ?: strdup("cpu");
+}
+
 struct perf_pmu *evsel__find_pmu(const struct evsel *evsel)
 {
 	struct perf_pmu *pmu = evsel->pmu;