perf: Fix the missing event initialization when pmu is found in idr

Currently, the event is not initialized if pmu is found in idr. This
never causes bug just because now no pmu is associated with the idr
id.

Signed-off-by: Lin Ming <ming.m.lin@intel.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1298812411.2699.9.camel@localhost>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/perf_event.c

@@ -6098,17 +6098,22 @@ struct pmu *perf_init_event(struct perf_event *event)
 {
 	struct pmu *pmu = NULL;
 	int idx;
+	int ret;
 
 	idx = srcu_read_lock(&pmus_srcu);
 
 	rcu_read_lock();
 	pmu = idr_find(&pmu_idr, event->attr.type);
 	rcu_read_unlock();
-	if (pmu)
+	if (pmu) {
+		ret = pmu->event_init(event);
+		if (ret)
+			pmu = ERR_PTR(ret);
 		goto unlock;
+	}
 
 	list_for_each_entry_rcu(pmu, &pmus, entry) {
-		int ret = pmu->event_init(event);
+		ret = pmu->event_init(event);
 		if (!ret)
 			goto unlock;