Re: [PATCH 4/9] s390/irq: utilize RCU instead of irq_lock_sparse() in show_msi_interrupt()

[Pingfan Liu <kernelfans@gmail.com>]

On Thu, Apr 21, 2022 at 01:42:59PM +0200, Heiko Carstens wrote:
> On Thu, Apr 21, 2022 at 11:36:17AM +0800, Pingfan Liu wrote:
> > Oops. You are right. What about using rcu_read_lock() directly?
> > 
> > 
> > diff --git a/arch/s390/kernel/irq.c b/arch/s390/kernel/irq.c
> > index 3033f616e256..45393919fe61 100644
> > --- a/arch/s390/kernel/irq.c
> > +++ b/arch/s390/kernel/irq.c
> > @@ -205,7 +205,7 @@ static void show_msi_interrupt(struct seq_file *p, int irq)
> >  	unsigned long flags;
> >  	int cpu;
> >  
> > -	irq_lock_sparse();
> > +	rcu_read_lock();
> >  	desc = irq_to_desc(irq);
> >  	if (!desc)
> >  		goto out;
> > @@ -224,7 +224,7 @@ static void show_msi_interrupt(struct seq_file *p, int irq)
> >  	seq_putc(p, '\n');
> >  	raw_spin_unlock_irqrestore(&desc->lock, flags);
> >  out:
> > -	irq_unlock_sparse();
> > +	rcu_read_unlock();
> 
> That looks like it should work. Please resend and also add a reference
> to commit 74bdf7815dfb ("genirq: Speedup show_interrupts()") which
> explains why this works.

Thanks for your review. I will follow up with V2.

Regards,

	Pingfan