perf/core: Simplify the perf_pmu_register() error path

The error path of perf_pmu_register() is of course very similar to a
subset of perf_pmu_unregister(). Extract this common part in
perf_pmu_free() and simplify things.

[ mingo: Forward ported it ]

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Ravi Bangoria <ravi.bangoria@amd.com>
Link: https://lore.kernel.org/r/20241104135518.090915501@infradead.org

kernel/events/core.c

@@ -11675,11 +11675,6 @@ static int perf_event_idx_default(struct perf_event *event)
 	return 0;
 }
 
-static void free_pmu_context(struct pmu *pmu)
-{
-	free_percpu(pmu->cpu_pmu_context);
-}
-
 /*
  * Let userspace know that this PMU supports address range filtering:
  */
@@ -11885,6 +11880,7 @@ static int pmu_dev_alloc(struct pmu *pmu)
 
 free_dev:
 	put_device(pmu->dev);
+	pmu->dev = NULL;
 	goto out;
 }
 
@@ -11906,25 +11902,38 @@ static bool idr_cmpxchg(struct idr *idr, unsigned long id, void *old, void *new)
 	return true;
 }
 
+static void perf_pmu_free(struct pmu *pmu)
+{
+	free_percpu(pmu->pmu_disable_count);
+	if (pmu_bus_running && pmu->dev && pmu->dev != PMU_NULL_DEV) {
+		if (pmu->nr_addr_filters)
+			device_remove_file(pmu->dev, &dev_attr_nr_addr_filters);
+		device_del(pmu->dev);
+		put_device(pmu->dev);
+	}
+	free_percpu(pmu->cpu_pmu_context);
+}
+
 int perf_pmu_register(struct pmu *pmu, const char *name, int type)
 {
 	int cpu, ret, max = PERF_TYPE_MAX;
 
+	pmu->type = -1;
+
 	mutex_lock(&pmus_lock);
 	ret = -ENOMEM;
 	pmu->pmu_disable_count = alloc_percpu(int);
 	if (!pmu->pmu_disable_count)
 		goto unlock;
 
-	pmu->type = -1;
 	if (WARN_ONCE(!name, "Can not register anonymous pmu.\n")) {
 		ret = -EINVAL;
-		goto free_pdc;
+		goto free;
 	}
 
 	if (WARN_ONCE(pmu->scope >= PERF_PMU_MAX_SCOPE, "Can not register a pmu with an invalid scope.\n")) {
 		ret = -EINVAL;
-		goto free_pdc;
+		goto free;
 	}
 
 	pmu->name = name;
@@ -11934,24 +11943,23 @@ int perf_pmu_register(struct pmu *pmu, const char *name, int type)
 
 	ret = idr_alloc(&pmu_idr, NULL, max, 0, GFP_KERNEL);
 	if (ret < 0)
-		goto free_pdc;
+		goto free;
 
 	WARN_ON(type >= 0 && ret != type);
 
-	type = ret;
-	pmu->type = type;
+	pmu->type = ret;
 	atomic_set(&pmu->exclusive_cnt, 0);
 
 	if (pmu_bus_running && !pmu->dev) {
 		ret = pmu_dev_alloc(pmu);
 		if (ret)
-			goto free_idr;
+			goto free;
 	}
 
 	ret = -ENOMEM;
 	pmu->cpu_pmu_context = alloc_percpu(struct perf_cpu_pmu_context);
 	if (!pmu->cpu_pmu_context)
-		goto free_dev;
+		goto free;
 
 	for_each_possible_cpu(cpu) {
 		struct perf_cpu_pmu_context *cpc;
@@ -11992,8 +12000,10 @@ int perf_pmu_register(struct pmu *pmu, const char *name, int type)
 	/*
 	 * Now that the PMU is complete, make it visible to perf_try_init_event().
 	 */
-	if (!idr_cmpxchg(&pmu_idr, pmu->type, NULL, pmu))
-		goto free_context;
+	if (!idr_cmpxchg(&pmu_idr, pmu->type, NULL, pmu)) {
+		ret = -EINVAL;
+		goto free;
+	}
 	list_add_rcu(&pmu->entry, &pmus);
 
 	ret = 0;
@@ -12002,20 +12012,10 @@ int perf_pmu_register(struct pmu *pmu, const char *name, int type)
 
 	return ret;
 
-free_context:
-	free_percpu(pmu->cpu_pmu_context);
-
-free_dev:
-	if (pmu->dev && pmu->dev != PMU_NULL_DEV) {
-		device_del(pmu->dev);
-		put_device(pmu->dev);
-	}
-
-free_idr:
-	idr_remove(&pmu_idr, pmu->type);
-
-free_pdc:
-	free_percpu(pmu->pmu_disable_count);
+free:
+	if (pmu->type >= 0)
+		idr_remove(&pmu_idr, pmu->type);
+	perf_pmu_free(pmu);
 	goto unlock;
 }
 EXPORT_SYMBOL_GPL(perf_pmu_register);
@@ -12034,14 +12034,7 @@ void perf_pmu_unregister(struct pmu *pmu)
 	synchronize_srcu(&pmus_srcu);
 	synchronize_rcu();
 
-	free_percpu(pmu->pmu_disable_count);
-	if (pmu_bus_running && pmu->dev && pmu->dev != PMU_NULL_DEV) {
-		if (pmu->nr_addr_filters)
-			device_remove_file(pmu->dev, &dev_attr_nr_addr_filters);
-		device_del(pmu->dev);
-		put_device(pmu->dev);
-	}
-	free_pmu_context(pmu);
+	perf_pmu_free(pmu);
 }
 EXPORT_SYMBOL_GPL(perf_pmu_unregister);