[RFC][PATCH 2/9] perf: core, remove hw_perf_event_init

[Lin Ming]

A new field "pmu_id" is added to struct perf_event_attr.

2 new functions: perf_event_register_pmu, perf_event_lookup_pmu
perf_event_register_pmu: the pmu registration facility
perf_event_lookup_pmu: lookup the pmu via the passed in event->attr.pmu_id.

A new api pmu->init_event to replace hw_perf_event_init

Signed-off-by: Lin Ming <ming.m.lin@xxxxxxxxx>
---
 include/linux/perf_event.h |    9 +++++++++
 kernel/perf_event.c        |   39 +++++++++++++++++++++++++++++++--------
 2 files changed, 40 insertions(+), 8 deletions(-)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 5856d3b..6246c99 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -225,6 +225,8 @@ struct perf_event_attr {
 	__u32			bp_type;
 	__u64			bp_addr;
 	__u64			bp_len;
+
+	int			pmu_id;
 };
 
 /*
@@ -553,6 +555,9 @@ struct perf_event;
  * struct pmu - generic performance monitoring unit
  */
 struct pmu {
+	int id;
+	struct list_head entry;
+
 	int (*enable)			(struct perf_event *event);
 	void (*disable)			(struct perf_event *event);
 	int (*start)			(struct perf_event *event);
@@ -569,6 +574,8 @@ struct pmu {
 	void (*start_txn)	(struct pmu *pmu);
 	void (*cancel_txn)	(struct pmu *pmu);
 	int  (*commit_txn)	(struct pmu *pmu);
+
+	int  (*init_event)	(struct perf_event *event);
 };
 
 /**
@@ -1014,6 +1021,8 @@ extern int perf_swevent_get_recursion_context(void);
 extern void perf_swevent_put_recursion_context(int rctx);
 extern void perf_event_enable(struct perf_event *event);
 extern void perf_event_disable(struct perf_event *event);
+
+extern void perf_event_register_pmu(struct pmu *pmu);
 #else
 static inline void
 perf_event_task_sched_in(struct task_struct *task)			{ }
diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index 36baf85..f19d40e 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -40,6 +40,12 @@
  */
 static DEFINE_PER_CPU(struct perf_cpu_context, perf_cpu_context);
 
+/*
+ * The list of multiple hw pmus
+ */
+static struct list_head pmus;
+static int pmu_id_curr;
+
 int perf_max_events __read_mostly = 1;
 static int perf_reserved_percpu __read_mostly;
 static int perf_overcommit __read_mostly = 1;
@@ -75,11 +81,6 @@ static DEFINE_SPINLOCK(perf_resource_lock);
 /*
  * Architecture provided APIs - weak aliases:
  */
-extern __weak struct pmu *hw_perf_event_init(struct perf_event *event)
-{
-	return NULL;
-}
-
 void __weak hw_perf_disable(void)		{ barrier(); }
 void __weak hw_perf_enable(void)		{ barrier(); }
 
@@ -4670,6 +4671,19 @@ static struct pmu *sw_perf_event_init(struct perf_event *event)
 	return pmu;
 }
 
+static struct pmu *perf_event_lookup_pmu(struct perf_event *event)
+{
+	struct pmu *pmu;
+	int pmu_id = event->attr.pmu_id;
+
+	list_for_each_entry(pmu, &pmus, entry) {
+		if (pmu->id == pmu_id)
+			return pmu;
+	}
+
+	return NULL;
+}
+
 /*
  * Allocate and initialize a event structure
  */
@@ -4685,7 +4699,7 @@ perf_event_alloc(struct perf_event_attr *attr,
 	struct pmu *pmu;
 	struct perf_event *event;
 	struct hw_perf_event *hwc;
-	long err;
+	long err = 0;
 
 	event = kzalloc(sizeof(*event), gfpflags);
 	if (!event)
@@ -4750,7 +4764,9 @@ perf_event_alloc(struct perf_event_attr *attr,
 	case PERF_TYPE_RAW:
 	case PERF_TYPE_HARDWARE:
 	case PERF_TYPE_HW_CACHE:
-		pmu = hw_perf_event_init(event);
+		pmu = perf_event_lookup_pmu(event);
+		if (pmu && pmu->init_event)
+			err = pmu->init_event(event);
 		break;
 
 	case PERF_TYPE_SOFTWARE:
@@ -4770,7 +4786,6 @@ perf_event_alloc(struct perf_event_attr *attr,
 		break;
 	}
 done:
-	err = 0;
 	if (!pmu)
 		err = -EINVAL;
 	else if (IS_ERR(pmu))
@@ -5627,6 +5642,8 @@ void __init perf_event_init(void)
 	perf_cpu_notify(&perf_cpu_nb, (unsigned long)CPU_ONLINE,
 			(void *)(long)smp_processor_id());
 	register_cpu_notifier(&perf_cpu_nb);
+
+	INIT_LIST_HEAD(&pmus);
 }
 
 static ssize_t perf_show_reserve_percpu(struct sysdev_class *class,
@@ -5726,3 +5743,9 @@ static int __init perf_event_sysfs_init(void)
 				  &perfclass_attr_group);
 }
 device_initcall(perf_event_sysfs_init);
+
+void perf_event_register_pmu(struct pmu *pmu)
+{
+	pmu->id = pmu_id_curr++;
+	list_add_tail(&pmu->entry, &pmus);
+}


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