Re: [PATCH] sofirq: make rcu_irq_enter()/rcu_irq_exit() called in pairs

["Paul E. McKenney" <paulmck@linux.vnet.ibm.com>]

On Tue, Oct 27, 2009 at 04:00:11PM +0800, Lai Jiangshan wrote:
> 
> irq_enter() calls rcu_irq_enter() unconditionally,
> the same as irq_exit() calls rcu_irq_exit().
> 
> It does not change the binary because rcu_irq_enter()
> is dummy when !CONFIG_NO_HZ.
> 
> It's just a cleanup.

This does look like a nice cleanup!  I will pull it in and test it.

Yes, it should be provably the same, but RCU has taught me to be quite
paranoid.  ;-)

						Thanx, Paul

> Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
> ---
> diff --git a/kernel/softirq.c b/kernel/softirq.c
> index f8749e5..21939d9 100644
> --- a/kernel/softirq.c
> +++ b/kernel/softirq.c
> @@ -302,9 +302,9 @@ void irq_exit(void)
>  	if (!in_interrupt() && local_softirq_pending())
>  		invoke_softirq();
> 
> +	rcu_irq_exit();
>  #ifdef CONFIG_NO_HZ
>  	/* Make sure that timer wheel updates are propagated */
> -	rcu_irq_exit();
>  	if (idle_cpu(smp_processor_id()) && !in_interrupt() && !need_resched())
>  		tick_nohz_stop_sched_tick(0);
>  #endif
>