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Date: Mon, 5 Jun 2006 14:51:32 +0200
To: linux-kernel@vger.kernel.org
Subject: debugging "irq 7: nobody cared" in my module
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From: Thomas Andrews <tandrews@grok.co.za>
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Hi,

What can cause "irq x: nobody cared" ? On exit from my IRQ handler, I am
checking to make sure that there are no residual/pending unhandled
events on exit. Here is part of my handler:

irqreturn_t scx200_acb_irq(int irq_no, void *dev_id, struct pt_regs *regs)
{
    struct scx200_acb_iface *iface = dev_id;
    unsigned long flags;
    spin_lock_irqsave(lock, flags);
    if (inb(ACBST)) {
//      tasklet_schedule(&iface->tasklet);
        scx200_acb_machine(iface, inb(ACBST));
        if (iface->state == state_idle)     /* Finished */
            wake_up_interruptible(&iface->acb_queue);
    } else {
        /* Should never get here */
        printk("causeless IRQ!\n");
        /* Reset the ACB to clear any pending IRQ */
        outb((inb(ACBCTL2) & 0xfe), ACBCTL2);
        outb((inb(ACBCTL2) | 0x01), ACBCTL2);
    }
    /* Check to see if some event was not handled */
    if (inb(ACBST) & 0xBC)
        printk("============== ACBST=%#x ===============\n",inb(ACBST));
    spin_unlock_irqrestore(lock, flags);
    return IRQ_RETVAL(0);
}

I've also had the problem when I move everything into a tasklet, and
just have a very short IRQ handler.

Many thanks,
Thomas