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

[Raghavendra D Prabhu]

Hi,


* On Mon, Sep 10, 2012 at 09:41:49AM -0400, Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx> wrote:
> On 12-09-09 03:25 PM, raghu.prabhu13@xxxxxxxxx wrote:
> > From: Raghavendra D Prabhu <rprabhu@xxxxxxxxxxx>
> >
> > 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?

I have seen it reported in many places like 
https://bugzilla.redhat.com/show_bug.cgi?id=225399 and 
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/480997

> 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.

I just realized that handler_irq checks for < NR_IRQS where the 
underflow will fail and will return. So this patch is not required.

However,  I think we need to fix the unsigned / int mixup by 
assigning vector_irq[..] to NR_IRQS+1  as guard value and 
changing unsigned to signed as in patch.
> 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@xxxxxxxxxxx>
> > ---
> >  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);




Regards,
--
Raghavendra Prabhu
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