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.gortma...@windriver.com> wrote:

On 12-09-09 03:25 PM, raghu.prabh...@gmail.com wrote:

From: Raghavendra D Prabhu <rpra...@wnohang.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?

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 <rpra...@wnohang.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);

Regards,
--
Raghavendra Prabhu
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