linux-kernel - Re: [patch 05/46] genirq/resend: Switch to lock guards

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Message-ID: <b0e222ca-0226-45fc-b348-fd21f691a466@linux.ibm.com>
Date: Mon, 17 Mar 2025 13:52:52 +0530
From: Shrikanth Hegde <sshegde@...ux.ibm.com>
To: Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>
Cc: Jiri Slaby <jirislaby@...nel.org>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [patch 05/46] genirq/resend: Switch to lock guards

Hi Thomas.

On 3/13/25 21:29, Thomas Gleixner wrote:
> Convert all lock/unlock pairs to guards and tidy up the code.
> 
> No functional change.
> 
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> ---
>   kernel/irq/resend.c |   50 +++++++++++++++++++++-----------------------------
>   1 file changed, 21 insertions(+), 29 deletions(-)
> 
> --- a/kernel/irq/resend.c
> +++ b/kernel/irq/resend.c
> @@ -30,18 +30,17 @@ static DEFINE_RAW_SPINLOCK(irq_resend_lo
>    */
>   static void resend_irqs(struct tasklet_struct *unused)
>   {
> -	struct irq_desc *desc;
> -
> -	raw_spin_lock_irq(&irq_resend_lock);
> +	guard(raw_spinlock_irq)(&irq_resend_lock);
>   	while (!hlist_empty(&irq_resend_list)) {
> -		desc = hlist_entry(irq_resend_list.first, struct irq_desc,
> -				   resend_node);
> +		struct irq_desc *desc;
> +
> +		desc = hlist_entry(irq_resend_list.first, struct irq_desc,  resend_node);
>   		hlist_del_init(&desc->resend_node);
> +
>   		raw_spin_unlock(&irq_resend_lock);
>   		desc->handle_irq(desc);
>   		raw_spin_lock(&irq_resend_lock);
>   	}
> -	raw_spin_unlock_irq(&irq_resend_lock);
>   }
>   
>   /* Tasklet to handle resend: */
> @@ -75,19 +74,18 @@ static int irq_sw_resend(struct irq_desc
>   	}
>   
>   	/* Add to resend_list and activate the softirq: */
> -	raw_spin_lock(&irq_resend_lock);
> -	if (hlist_unhashed(&desc->resend_node))
> -		hlist_add_head(&desc->resend_node, &irq_resend_list);
> -	raw_spin_unlock(&irq_resend_lock);
> +	scoped_guard (raw_spinlock, &irq_resend_lock) {

Nit: Any reason why it is "scoped_guard ()" instead of "scoped_guard()". 
Is there a difference between the two?

I have seen in the current code base both are present, i would be nice 
to have one of it no? or guideline on which one to use when?

> +		if (hlist_unhashed(&desc->resend_node))
> +			hlist_add_head(&desc->resend_node, &irq_resend_list);
> +	}
>   	tasklet_schedule(&resend_tasklet);
>   	return 0;
>   }
>   
>   void clear_irq_resend(struct irq_desc *desc)
>   {
> -	raw_spin_lock(&irq_resend_lock);
> +	guard(raw_spinlock)(&irq_resend_lock);
>   	hlist_del_init(&desc->resend_node);
> -	raw_spin_unlock(&irq_resend_lock);
>   }
>   
>   void irq_resend_init(struct irq_desc *desc)
> @@ -172,30 +170,24 @@ int check_irq_resend(struct irq_desc *de
>    */
>   int irq_inject_interrupt(unsigned int irq)
>   {
> -	struct irq_desc *desc;
> -	unsigned long flags;
> -	int err;
> +	int err = -EINVAL;
>   
>   	/* Try the state injection hardware interface first */
>   	if (!irq_set_irqchip_state(irq, IRQCHIP_STATE_PENDING, true))
>   		return 0;
>   
>   	/* That failed, try via the resend mechanism */
> -	desc = irq_get_desc_buslock(irq, &flags, 0);
> -	if (!desc)
> -		return -EINVAL;
> +	scoped_irqdesc_get_and_buslock(irq, 0) {
> +		struct irq_desc *desc = scoped_irqdesc;
>   
> -	/*
> -	 * Only try to inject when the interrupt is:
> -	 *  - not NMI type
> -	 *  - activated
> -	 */
> -	if (irq_is_nmi(desc) || !irqd_is_activated(&desc->irq_data))
> -		err = -EINVAL;
> -	else
> -		err = check_irq_resend(desc, true);
> -
> -	irq_put_desc_busunlock(desc, flags);
> +		/*
> +		 * Only try to inject when the interrupt is:
> +		 *  - not NMI type
> +		 *  - activated
> +		 */
> +		if (!irq_is_nmi(desc) && irqd_is_activated(&desc->irq_data))
> +			err = check_irq_resend(desc, true);
> +	}
>   	return err;
>   }
>   EXPORT_SYMBOL_GPL(irq_inject_interrupt);
> 
>