[PATCH v1 22/25] perf pmu: Scan type early to fail an invalid PMU quickly

[Ian Rogers <irogers@google.com>]

Scan sysfs PMU's type early so that format and aliases aren't
attempted to be loaded if the PMU name is invalid. This is the case
for event_pmu tokens in parse-events.y where a wildcard name is first
assumed to be a PMU name.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/util/pmu.c | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
index 81a40fe02d65..b4ba4f7f5e18 100644
--- a/tools/perf/util/pmu.c
+++ b/tools/perf/util/pmu.c
@@ -953,12 +953,21 @@ struct perf_pmu *perf_pmu__lookup(struct list_head *pmus, int dirfd, const char
 	if (!pmu)
 		return NULL;
 
-	INIT_LIST_HEAD(&pmu->format);
-	INIT_LIST_HEAD(&pmu->aliases);
-	INIT_LIST_HEAD(&pmu->caps);
 	pmu->name = strdup(name);
 	if (!pmu->name)
 		goto err;
+
+	/*
+	 * Read type early to fail fast if a lookup name isn't a PMU. Ensure
+	 * that type value is successfully assigned (return 1).
+	 */
+	if (perf_pmu__scan_file_at(pmu, dirfd, "type", "%u", &type) != 1)
+		goto err;
+
+	INIT_LIST_HEAD(&pmu->format);
+	INIT_LIST_HEAD(&pmu->aliases);
+	INIT_LIST_HEAD(&pmu->caps);
+
 	/*
 	 * The pmu data we store & need consists of the pmu
 	 * type value and format definitions. Load both right
@@ -978,10 +987,6 @@ struct perf_pmu *perf_pmu__lookup(struct list_head *pmus, int dirfd, const char
 	pmu->is_core = is_pmu_core(name);
 	pmu->cpus = pmu_cpumask(dirfd, name, pmu->is_core);
 
-	/* Read type, and ensure that type value is successfully assigned (return 1) */
-	if (perf_pmu__scan_file_at(pmu, dirfd, "type", "%u", &type) != 1)
-		goto err;
-
 	alias_name = pmu_find_alias_name(name);
 	if (alias_name) {
 		pmu->alias_name = strdup(alias_name);
@@ -1007,7 +1012,6 @@ struct perf_pmu *perf_pmu__lookup(struct list_head *pmus, int dirfd, const char
 	return NULL;
 }
 
-
 /* Creates the PMU when sysfs scanning fails. */
 struct perf_pmu *perf_pmu__create_placeholder_core_pmu(struct list_head *core_pmus)
 {
-- 
2.42.0.rc1.204.g551eb34607-goog