Commit 9babcd79 authored Oct 08, 2015 by Daniel Bristot de Oliveira Committed by Ingo Molnar Oct 12, 2015

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 <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>

parent 25cb62b7

kernel/sched/idle.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -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;

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