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

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 <[email protected]>
Reviewed-by: Luis Claudio R. Goncalves <[email protected]>
Acked-by: Steven Rostedt <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Mike Galbraith <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Link: http://lkml.kernel.org/r/10fc3705874aef11dbe152a068b591a7be1899b4.1444314899.git.bristot@redhat.com
Signed-off-by: Ingo Molnar <[email protected]>

diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
index 8f177c73ae199ba41878fea8de9a5b0a7196620a..4a2ef5a02fd3f91d7c4228378c23d5606bb73812 100644 (file)
--- 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;