Re: [PATCH V3 2/6] sched: idle: cpuidle: Check the latency req before idle

On Fri, Nov 07, 2014 at 03:31:23PM +0100, Daniel Lezcano wrote:

@@ -216,19 +219,26 @@ static void cpu_idle_loop(void) local_irq_disable(); arch_cpu_idle_enter();

• 	latency_req = pm_qos_request(PM_QOS_CPU_DMA_LATENCY);
  

• /*
   * In poll mode we reenable interrupts and spin.
   *
  

• 	 * If the latency req is zero, we don't want to
  

• 	 * enter any idle state and we jump to the poll
  

• 	 * function directly
  

• 	 *
   * Also if we detected in the wakeup from idle
   * path that the tick broadcast device expired
   * for us, we don't want to go deep idle as we
   * know that the IPI is going to arrive right
   * away
   */
  

• 	if (cpu_idle_force_poll || tick_check_broadcast_expired())
  

• 	if (!latency_req || cpu_idle_force_poll ||
  

• 	    tick_check_broadcast_expired())
  	cpu_idle_poll();
  

Is this why you wanted that weak poll function?

Should we not instead allow an arch to deal with !latency_req and only fall back to this polling if there is no actual way for it to implement this better?