perf: Introduce is_sampling_event()

and use it when appropriate.
Signed-off-by: Franck Bui-Huu <fbuihuu@gmail.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1290525705-6265-1-git-send-email-fbuihuu@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/cpu/perf_event.c

@@ -442,7 +442,7 @@ static int x86_setup_perfctr(struct perf_event *event)
 	struct hw_perf_event *hwc = &event->hw;
 	u64 config;
 
-	if (!hwc->sample_period) {
+	if (!is_sampling_event(event)) {
 		hwc->sample_period = x86_pmu.max_period;
 		hwc->last_period = hwc->sample_period;
 		local64_set(&hwc->period_left, hwc->sample_period);

include/linux/perf_event.h

@@ -969,6 +969,11 @@ extern int perf_event_overflow(struct perf_event *event, int nmi,
 				 struct perf_sample_data *data,
 				 struct pt_regs *regs);
 
+static inline bool is_sampling_event(struct perf_event *event)
+{
+	return event->attr.sample_period != 0;
+}
+
 /*
  * Return 1 for a software event, 0 for a hardware event
  */

kernel/perf_event.c

@@ -2514,7 +2514,7 @@ static int perf_event_period(struct perf_event *event, u64 __user *arg)
 	int ret = 0;
 	u64 value;
 
-	if (!event->attr.sample_period)
+	if (!is_sampling_event(event))
 		return -EINVAL;
 
 	if (copy_from_user(&value, arg, sizeof(value)))
@@ -4385,7 +4385,7 @@ static void perf_swevent_event(struct perf_event *event, u64 nr,
 	if (!regs)
 		return;
 
-	if (!hwc->sample_period)
+	if (!is_sampling_event(event))
 		return;
 
 	if (nr == 1 && hwc->sample_period == 1 && !event->attr.freq)
@@ -4548,7 +4548,7 @@ static int perf_swevent_add(struct perf_event *event, int flags)
 	struct hw_perf_event *hwc = &event->hw;
 	struct hlist_head *head;
 
-	if (hwc->sample_period) {
+	if (is_sampling_event(event)) {
 		hwc->last_period = hwc->sample_period;
 		perf_swevent_set_period(event);
 	}
@@ -4920,7 +4920,7 @@ static void perf_swevent_start_hrtimer(struct perf_event *event)
 
 	hrtimer_init(&hwc->hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 	hwc->hrtimer.function = perf_swevent_hrtimer;
-	if (hwc->sample_period) {
+	if (is_sampling_event(event)) {
 		s64 period = local64_read(&hwc->period_left);
 
 		if (period) {
@@ -4941,7 +4941,7 @@ static void perf_swevent_cancel_hrtimer(struct perf_event *event)
 {
 	struct hw_perf_event *hwc = &event->hw;
 
-	if (hwc->sample_period) {
+	if (is_sampling_event(event)) {
 		ktime_t remaining = hrtimer_get_remaining(&hwc->hrtimer);
 		local64_set(&hwc->period_left, ktime_to_ns(remaining));