Re: [PATCH V3 1/6] sched: idle: Add a weak arch_cpu_idle_poll function

On Fri, Nov 07, 2014 at 03:31:22PM +0100, Daniel Lezcano wrote:

The poll function is called when a timer expired or if we force to poll when the cpu_idle_force_poll option is set.

The poll function does:

   local_irq_enable();
   while (!tif_need_resched())
           cpu_relax();

This default poll function suits for the x86 arch because its rep; nop; hardware power optimization. But on other archs, this optimization does not exists and we are not saving power. The arch specific bits may want to optimize this loop by adding their own optimization.

This doesn't make sense to me; should an arch not either implement an actual idle driver or implement cpu_relax() properly, why allow for a third weird option?