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

From: Raghavendra D Prabhu
Date: Fri Sep 14 2012 - 22:56:01 EST


* 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

I have seen it reported in many places like and

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

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.


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 = __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)) {

- 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);



Raghavendra Prabhu
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