Re: [patch 05/34] idle: Implement generic idle function

Heiko Carstens
2013-03-23T08:56:56Z

On Thu, Mar 21, 2013 at 09:53:00PM -0000, Thomas Gleixner wrote:
> All idle functions in arch/* are more or less the same, plus minus a
> few bugs and extra instrumentation, tickless support and other
> optional items.
>
> Implement a generic idle function which resembles the functionality
> found in arch/. Provide weak arch_cpu_idle_* functions which can be
> overridden by the architecture code if needed.
>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

[...]

> +static void cpu_idle_loop(void)
> +{
> + while (1) {
> + tick_nohz_idle_enter();
> +
> + while (!need_resched()) {
> + check_pgt_cache();
> + rmb();
> +
> + if (cpu_is_offline(smp_processor_id()))
> + arch_cpu_idle_dead();
> +
> + local_irq_disable();
> + arch_cpu_idle_enter();
> +
> + if (cpu_idle_force_poll) {
> + cpu_idle_poll();
> + } else {
> + current_clr_polling();
> + if (!need_resched()) {
> + stop_critical_timings();
> + rcu_idle_enter();
> + arch_cpu_idle();
> + WARN_ON_ONCE(!irqs_disabled());

This should be WARN_ON_ONCE(irqs_disabled()), no?

> + rcu_idle_exit();
> + start_critical_timings();
> + } else {
> + local_irq_enable();
> + }
> + current_set_polling();
> + }
> + arch_cpu_idle_exit();
> + }
> + tick_nohz_idle_exit();

I was wondering why the scheduler doesn't complain when being called with
irqs disabled. In fact tick_nohz_idle_exit() enables irqs unconditionally
iff CONFIG_NO_HZ is set.

> + schedule_preempt_disabled();
> + }
> +}
> +
> +void cpu_startup_entry(enum cpuhp_state state)
> +{
> + current_set_polling();
> + arch_cpu_idle_prepare();
> + cpu_idle_loop();
> +}
> +#endif