On Friday 18 January 2013, Vineet Gupta wrote:
> +void cpu_idle(void)
> +{
> + /* Since we SLEEP in idle loop, TIF_POLLING_NRFLAG can't be set */
> +
> + /* endless idle loop with no priority at all */
> + while (1) {
> + tick_nohz_idle_enter();
> + rcu_idle_enter();
> +
> + while (!need_resched())
> + arch_idle();
> +
> + rcu_idle_exit();
> + tick_nohz_idle_exit();
> +
> + schedule_preempt_disabled();
> + }
> +}
Unless I'm mistaken, you have introduced the classic sleep race
here, where an interrupt can happen between the check for
need_resched() and the sleep instruction in arch_idle().
To avoid that, you need to disable interrupts around
the inner loop. The sleep instruction should return with
interrupts implicitly enabled if ARC behaves like most
other architectures doing this.
Arnd
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