perf_counter: fix hrtimer sampling

Impact: fix deadlock with perfstat

Fix for the perfstat fubar..

We cannot unconditionally call hrtimer_cancel() without ever having done
hrtimer_init() on the thing.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Orig-LKML-Reference: <1236959027.22447.149.camel@twins>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/perf_counter.c

@@ -1571,9 +1571,9 @@ static int cpu_clock_perf_counter_enable(struct perf_counter *counter)
 	int cpu = raw_smp_processor_id();
 
 	atomic64_set(&hwc->prev_count, cpu_clock(cpu));
-	if (hwc->irq_period) {
 	hrtimer_init(&hwc->hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 	hwc->hrtimer.function = perf_swcounter_hrtimer;
+	if (hwc->irq_period) {
 		__hrtimer_start_range_ns(&hwc->hrtimer,
 				ns_to_ktime(hwc->irq_period), 0,
 				HRTIMER_MODE_REL, 0);
@@ -1635,9 +1635,9 @@ static int task_clock_perf_counter_enable(struct perf_counter *counter)
 	struct hw_perf_counter *hwc = &counter->hw;
 
 	atomic64_set(&hwc->prev_count, task_clock_perf_counter_val(counter, 0));
-	if (hwc->irq_period) {
 	hrtimer_init(&hwc->hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 	hwc->hrtimer.function = perf_swcounter_hrtimer;
+	if (hwc->irq_period) {
 		__hrtimer_start_range_ns(&hwc->hrtimer,
 				ns_to_ktime(hwc->irq_period), 0,
 				HRTIMER_MODE_REL, 0);