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

Heiko Carstens
2022-04-21T11:43:14Z

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.