Re: [PATCH v3] rcu: Allow to eliminate softirq processing from rcutree

[Sebastian Andrzej Siewior <bigeasy@linutronix.de>]

On 2019-03-20 16:46:01 [-0700], Paul E. McKenney wrote:
> Thank you!  I reverted v2 and applied this one with the same sort of
> update.  Testing is going well thus far aside from my failing to add
> the required "=0" after the rcutree.use_softirq.  I will probably not
> be the only one who will run afoul of this, so I updated the commit log
> and the documentation accordingly, as shown below.

perfect, thank you.

> 							Thanx, Paul
> 
> diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
> index f46b4af96ab9..b807204ffd83 100644
> --- a/kernel/rcu/tree_plugin.h
> +++ b/kernel/rcu/tree_plugin.h
> @@ -629,7 +609,10 @@ static void rcu_read_unlock_special(struct task_struct *t)
>  		/* Need to defer quiescent state until everything is enabled. */
>  		if (irqs_were_disabled) {
>  			/* Enabling irqs does not reschedule, so... */
> -			raise_softirq_irqoff(RCU_SOFTIRQ);
> +			if (!use_softirq)

that exclamation mark needs to go :/

> +				raise_softirq_irqoff(RCU_SOFTIRQ);
> +			else
> +				invoke_rcu_core();
>  		} else {
>  			/* Enabling BH or preempt does reschedule, so... */
>  			set_tsk_need_resched(current);

Sebastian