perf events: Don't generate events for the idle task when exclude_idle is set

Getting samples for the idle task is often not interesting, so
don't generate them when exclude_idle is set for the event in
question.
Signed-off-by: NSøren Sandmann Pedersen <sandmann@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
LKML-Reference: <ye8pr8fmlq7.fsf@camel16.daimi.au.dk>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

kernel/perf_event.c

@@ -3959,6 +3959,7 @@ static enum hrtimer_restart perf_swevent_hrtimer(struct hrtimer *hrtimer)
 		regs = task_pt_regs(current);
 
 	if (regs) {
+		if (!(event->attr.exclude_idle && current->pid == 0))
 			if (perf_event_overflow(event, 0, &data, regs))
 				ret = HRTIMER_NORESTART;
 	}