linux-kernel - Re: [PATCH] IRQ: Add a check for uninitialized irqs.

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Message-ID: <504DEE1D.3040704@windriver.com>
Date:	Mon, 10 Sep 2012 09:41:49 -0400
From:	Paul Gortmaker <paul.gortmaker@...driver.com>
To:	<raghu.prabhu13@...il.com>
CC:	<jeremy@...p.org>, <mingo@...hat.com>, <x86@...nel.org>,
	Raghavendra D Prabhu <rprabhu@...hang.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	liu chuansheng <chuansheng.liu@...el.com>,
	Fernando Luis Vazquez Cao <fernando@....ntt.co.jp>,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] IRQ: Add a check for uninitialized irqs.

On 12-09-09 03:25 PM, raghu.prabhu13@...il.com wrote:
> From: Raghavendra D Prabhu <rprabhu@...hang.net>
> 
> Errors like "do_IRQ: 0.84 No Irq handler for vector (irq -1)" have been reported
> earlier filling up the console/logs. So this adds a condition to check for

Reported by who, and where, and on what hardware, and under what
circumstances?

You are adding another if statement to the hot path of do_IRQ just
to mask some random unknown symptom. instead of trying to understand
(and then solve) what the real breakage is.  Which is not the right
approach.

Paul.
--

> uninitialized irqs so that it exits early and doesn't proceed further. Also, irq
> is made a signed integer, since if it is not mapped to a vector, it will be
> assigned -1 which will be UINT_MAX otherwise.
> 
> Signed-off-by: Raghavendra D Prabhu <rprabhu@...hang.net>
> ---
>  arch/x86/kernel/irq.c | 13 ++++++++-----
>  1 file changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c
> index d44f782..ddba63a 100644
> --- a/arch/x86/kernel/irq.c
> +++ b/arch/x86/kernel/irq.c
> @@ -184,21 +184,24 @@ unsigned int __irq_entry do_IRQ(struct pt_regs *regs)
>  
>  	/* high bit used in ret_from_ code  */
>  	unsigned vector = ~regs->orig_ax;
> -	unsigned irq;
> +	int irq;
>  
>  	irq_enter();
>  	exit_idle();
>  
> -	irq = __this_cpu_read(vector_irq[vector]);
> +	if (unlikely((irq = __this_cpu_read(vector_irq[vector])) == -1)) {
> +		pr_emerg_ratelimited("IRQ handler not setup for vector %u", vector);
> +		goto err_exit;
> +	}
>  
>  	if (!handle_irq(irq, regs)) {
>  		ack_APIC_irq();
>  
> -		if (printk_ratelimit())
> -			pr_emerg("%s: %d.%d No irq handler for vector (irq %d)\n",
> -				__func__, smp_processor_id(), vector, irq);
> +		pr_emerg_ratelimited("%s: %d.%d No irq handler for vector (irq %u)\n",
> +			__func__, smp_processor_id(), vector, irq);
>  	}
>  
> +err_exit:
>  	irq_exit();
>  
>  	set_irq_regs(old_regs);
> 
--
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