[RFC][PATCH 7/8] perf: Default PMU ops

[Peter Zijlstra]

Provide default implementations for the pmu txn methods, this allows
us to remove some conditional code.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
---
 kernel/perf_event.c |   45 +++++++++++++++++++++++++++++++++++----------
 1 file changed, 35 insertions(+), 10 deletions(-)

Index: linux-2.6/kernel/perf_event.c
===================================================================
--- linux-2.6.orig/kernel/perf_event.c
+++ linux-2.6/kernel/perf_event.c
@@ -656,17 +656,11 @@ group_sched_in(struct perf_event *group_
 {
 	struct perf_event *event, *partial_group = NULL;
 	struct pmu *pmu = group_event->pmu;
-	bool txn = false;
 
 	if (group_event->state == PERF_EVENT_STATE_OFF)
 		return 0;
 
-	/* Check if group transaction availabe */
-	if (pmu->start_txn)
-		txn = true;
-
-	if (txn)
-		pmu->start_txn(pmu);
+	pmu->start_txn(pmu);
 
 	if (event_sched_in(group_event, cpuctx, ctx)) {
 		if (txn)
@@ -684,7 +678,7 @@ group_sched_in(struct perf_event *group_
 		}
 	}
 
-	if (!txn || !pmu->commit_txn(pmu))
+	if (!pmu->commit_txn(pmu))
 		return 0;
 
 group_error:
@@ -699,8 +693,7 @@ group_error:
 	}
 	event_sched_out(group_event, cpuctx, ctx);
 
-	if (txn)
-		pmu->cancel_txn(pmu);
+	pmu->cancel_txn(pmu);
 
 	return -EAGAIN;
 }
@@ -4748,6 +4741,26 @@ static struct list_head pmus;
 static DEFINE_SPINLOCK(pmus_lock);
 static struct srcu_struct pmus_srcu;
 
+static void perf_pmu_nop(struct pmu *pmu)
+{
+}
+
+static void perf_pmu_start_txn(struct pmu *pmu)
+{
+	perf_disable_pmu(pmu);
+}
+
+static int perf_pmu_commit_txn(struct pmu *pmu)
+{
+	perf_enable_pmu(pmu);
+	return 0;
+}
+
+static void perf_pmu_cancel_txn(struct pmu *pmu)
+{
+	perf_enable_pmu(pmu);
+}
+
 int perf_pmu_register(struct pmu *pmu)
 {
 	int ret;
@@ -4757,6 +4770,18 @@ int perf_pmu_register(struct pmu *pmu)
 	pmu->pmu_disable_count = alloc_percpu(int);
 	if (!pmu->pmu_disable_count)
 		goto unlock;
+
+	if (!pmu->pmu_enable) {
+		pmu->pmu_enable  = perf_pmu_nop;
+		pmu->pmu_disable = perf_pmu_nop;
+	}
+
+	if (!pmu->start_txn) {
+		pmu->start_txn  = perf_pmu_start_txn;
+		pmu->commit_txn = perf_pmu_commit_txn;
+		pmu->cancel_txn = perf_pmu_cancel_txn;
+	}
+
 	list_add_rcu(&pmu->entry, &pmus);
 	ret = 0;
 unlock:


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