[PATCH v3 5/8] perf: Split perf_event_read_value()

[Sukadev Bhattiprolu]

Move the part of perf_event_read_value() that computes the event
counts and event times into a new function, perf_event_compute().

This would allow us to call perf_event_compute() independently.

Signed-off-by: Sukadev Bhattiprolu <sukadev at linux.vnet.ibm.com>

Changelog[v3]
	Rather than move perf_event_read() into callers and then
	rename, just move the computations into a separate function
	(redesign to address comment from Peter Zijlstra).
---
 kernel/events/core.c |   37 ++++++++++++++++++++++++-------------
 1 file changed, 24 insertions(+), 13 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 44fb89d..b1e9a42 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3704,6 +3704,29 @@ static int perf_release(struct inode *inode, struct file *file)
 	return 0;
 }
 
+static u64 perf_event_compute(struct perf_event *event, u64 *enabled,
+			      u64 *running)
+{
+	struct perf_event *child;
+	u64 total;
+
+	total = perf_event_count(event);
+
+	*enabled += event->total_time_enabled +
+			atomic64_read(&event->child_total_time_enabled);
+	*running += event->total_time_running +
+			atomic64_read(&event->child_total_time_running);
+
+	list_for_each_entry(child, &event->child_list, child_list) {
+		perf_event_read(child);
+		total += perf_event_count(child);
+		*enabled += child->total_time_enabled;
+		*running += child->total_time_running;
+	}
+
+	return total;
+}
+
 /*
  * Remove all orphanes events from the context.
  */
@@ -3742,7 +3765,6 @@ static void orphans_remove_work(struct work_struct *work)
 
 u64 perf_event_read_value(struct perf_event *event, u64 *enabled, u64 *running)
 {
-	struct perf_event *child;
 	u64 total = 0;
 
 	*enabled = 0;
@@ -3751,19 +3773,8 @@ u64 perf_event_read_value(struct perf_event *event, u64 *enabled, u64 *running)
 	mutex_lock(&event->child_mutex);
 
 	perf_event_read(event);
-	total += perf_event_count(event);
+	total = perf_event_compute(event, enabled, running);
 
-	*enabled += event->total_time_enabled +
-			atomic64_read(&event->child_total_time_enabled);
-	*running += event->total_time_running +
-			atomic64_read(&event->child_total_time_running);
-
-	list_for_each_entry(child, &event->child_list, child_list) {
-		perf_event_read(child);
-		total += perf_event_count(child);
-		*enabled += child->total_time_enabled;
-		*running += child->total_time_running;
-	}
 	mutex_unlock(&event->child_mutex);
 
 	return total;
-- 
1.7.9.5