sched, tracing: Stop/start critical timings around the idle=poll idle loop

Daniel Bristot de Oliveira · Ingo Molnar · commit 9babcd7929bc · 2015-10-12T09:45:25.000+02:00
When using idle=poll, the preemptoff tracer is always showing the idle task as the culprit for long latencies. That happens because critical timings are not stopped before idle loop. This patch stops critical timings before entering the idle loop, starting it again after the idle loop. This problem does not affect the irqsoff tracer because interruptions are enabled before entering the idle loop. Signed-off-by: Daniel Bristot de Oliveira <bristot@redhat.com> Reviewed-by: Luis Claudio R. Goncalves <lgoncalv@redhat.com> Acked-by: Steven Rostedt <rostedt@goodmis.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/10fc3705874aef11dbe152a068b591a7be1899b4.1444314899.git.bristot@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
@@ -57,9 +57,11 @@ static inline int cpu_idle_poll(void)
 	rcu_idle_enter();
 	trace_cpu_idle_rcuidle(0, smp_processor_id());
 	local_irq_enable();
+	stop_critical_timings();
 	while (!tif_need_resched() &&
 		(cpu_idle_force_poll || tick_check_broadcast_expired()))
 		cpu_relax();
+	start_critical_timings();
 	trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, smp_processor_id());
 	rcu_idle_exit();
 	return 1;
