[PATCH 1/8] squashed series - 20241008183501.1354695-1-lucas.demarchi at intel.com

[Lucas De Marchi]

Patches 2 and 3 of https://lore.kernel.org/all/20241008183501.1354695-1-lucas.demarchi@intel.com/
with the unused module var removed (pending for v2 after review).

Signed-off-by: Lucas De Marchi <lucas.demarchi at intel.com>
---
 include/linux/perf_event.h | 12 ++++++++++++
 kernel/events/core.c       | 37 ++++++++++++++++++++++++++++++++-----
 2 files changed, 44 insertions(+), 5 deletions(-)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index fb908843f2092..d6983dbf5a45b 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -561,6 +561,17 @@ struct pmu {
 	 * Check period value for PERF_EVENT_IOC_PERIOD ioctl.
 	 */
 	int (*check_period)		(struct perf_event *event, u64 value); /* optional */
+
+	/*
+	 * Optional: get a reference. Typically needed by PMUs that are bound to a device
+	 * that can be hotplugged, either physically or through sysfs' bind/unbind. When provided,
+	 * pmu::put() is mandatory and it's driver responsibility to call perf_pmu_free() when
+	 * resources can be released.
+	 */
+	struct pmu *(*get)		(struct pmu *pmu);
+
+	/* Optional: put a reference. See pmu::get() */
+	 void (*put)			(struct pmu *pmu);
 };
 
 enum perf_addr_filter_action_t {
@@ -1104,6 +1115,7 @@ extern void perf_event_itrace_started(struct perf_event *event);
 
 extern int perf_pmu_register(struct pmu *pmu, const char *name, int type);
 extern void perf_pmu_unregister(struct pmu *pmu);
+extern void perf_pmu_free(struct pmu *pmu);
 
 extern void __perf_event_task_sched_in(struct task_struct *prev,
 				       struct task_struct *task);
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 3b8b85adb10a9..2d39005ba6d9c 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -5319,6 +5319,20 @@ static void perf_pending_task_sync(struct perf_event *event)
 	rcuwait_wait_event(&event->pending_work_wait, !event->pending_work, TASK_UNINTERRUPTIBLE);
 }
 
+static void pmu_module_put(struct pmu **ppmu)
+{
+	struct pmu *pmu = *ppmu;
+	struct module *module = pmu->module;
+
+	if (pmu->put)
+		pmu->put(pmu);
+
+	module_put(module);
+
+	/* Can't touch pmu anymore/ */
+	*ppmu = NULL;
+}
+
 static void _free_event(struct perf_event *event)
 {
 	irq_work_sync(&event->pending_irq);
@@ -5374,7 +5388,8 @@ static void _free_event(struct perf_event *event)
 		put_ctx(event->ctx);
 
 	exclusive_event_destroy(event);
-	module_put(event->pmu->module);
+
+	pmu_module_put(&event->pmu);
 
 	call_rcu(&event->rcu_head, free_event_rcu);
 }
@@ -11512,10 +11527,12 @@ static int perf_event_idx_default(struct perf_event *event)
 	return 0;
 }
 
-static void free_pmu_context(struct pmu *pmu)
+void perf_pmu_free(struct pmu *pmu)
 {
 	free_percpu(pmu->cpu_pmu_context);
+	free_percpu(pmu->pmu_disable_count);
 }
+EXPORT_SYMBOL_GPL(perf_pmu_free);
 
 /*
  * Let userspace know that this PMU supports address range filtering:
@@ -11749,6 +11766,11 @@ int perf_pmu_register(struct pmu *pmu, const char *name, int type)
 		goto free_pdc;
 	}
 
+	if (WARN_ONCE((!!pmu->get) ^ (!!pmu->put), "Can not register a pmu with only get or put defined.\n")) {
+		ret = -EINVAL;
+		goto free_pdc;
+	}
+
 	pmu->name = name;
 
 	if (type >= 0)
@@ -11845,7 +11867,6 @@ void perf_pmu_unregister(struct pmu *pmu)
 	synchronize_srcu(&pmus_srcu);
 	synchronize_rcu();
 
-	free_percpu(pmu->pmu_disable_count);
 	idr_remove(&pmu_idr, pmu->type);
 	if (pmu_bus_running && pmu->dev && pmu->dev != PMU_NULL_DEV) {
 		if (pmu->nr_addr_filters)
@@ -11853,8 +11874,11 @@ void perf_pmu_unregister(struct pmu *pmu)
 		device_del(pmu->dev);
 		put_device(pmu->dev);
 	}
-	free_pmu_context(pmu);
+
 	mutex_unlock(&pmus_lock);
+
+	if (!pmu->put)
+		perf_pmu_free(pmu);
 }
 EXPORT_SYMBOL_GPL(perf_pmu_unregister);
 
@@ -11888,6 +11912,9 @@ static int perf_try_init_event(struct pmu *pmu, struct perf_event *event)
 		BUG_ON(!ctx);
 	}
 
+	if (pmu->get)
+		pmu->get(pmu);
+
 	event->pmu = pmu;
 	ret = pmu->event_init(event);
 
@@ -11924,7 +11951,7 @@ static int perf_try_init_event(struct pmu *pmu, struct perf_event *event)
 	}
 
 	if (ret)
-		module_put(pmu->module);
+		pmu_module_put(&pmu);
 
 	return ret;
 }
-- 
2.47.0