Re: [PATCH] v4 Teach RCU that idle task is not quiscent state atboot

[Ingo Molnar]

* Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> wrote:

> +/* Internal to kernel, but needed by rcupreempt.h. */
> +extern int rcu_idle_cpu_truthful;

The name sucks a bit ;-) 'truthful' is an emotionally laden 
statement and distracts from the technical purpose when reading 
it ;)

Same for:

> +extern void rcu_idle_now_means_idle(void);

Also, i'm wondering, is there really no way to avoid this quirk. 
We almost got away without it for a long time.

This one:

>  void rcu_check_callbacks(int cpu, int user)
>  {
>  	if (user ||
> -	    (idle_cpu(cpu) && !in_softirq() &&
> -				hardirq_count() <= (1 << HARDIRQ_SHIFT))) {
> +	    (idle_cpu(cpu) && rcu_idle_cpu_truthful &&
> +	     !in_softirq() && hardirq_count() <= (1 << HARDIRQ_SHIFT))) {

Is a hotpath called very often ...

	Ingo
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