linux-kernel - Threaded irq handler question

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Message-ID: <l2u87a5b0801004210935wf6ca2991ua777c39c737391f8@mail.gmail.com>
Date:	Wed, 21 Apr 2010 17:35:32 +0100
From:	Will Newton <will.newton@...il.com>
To:	Linux Kernel list <linux-kernel@...r.kernel.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>
Subject: Threaded irq handler question

Hi all,

I have a threaded irq handler attached to a level-triggered gpio
interrupt line. The check handler checks the status of the gpio line
and disables the irq line amd returns WAKE_THREAD in that case:

static irqreturn_t isr_check(int irq, void *p)
{
        if (gpio_status()) {
                disable_irq_nosync(irq);
                return IRQ_WAKE_THREAD;
        }

        return IRQ_NONE;
}

The thread then does some i2c transactions that will eventually
deassert the gpio line:

static irqreturn_t isr(int irq, void *p)
{
        /* do some i2c transfers */
        enable_irq(irq);
        return IRQ_HANDLED;
}

My problem is that this structure does not work, because once I call
disable_irq_nosync() on the irq in the check handler the thread will
no longer run because the irq is disabled. However if I don't call
disable_irq_nosync() I will get endless irqs because the line is
level-triggered and will not be deasserted until the thread has run.

Could someone tell me what I'm doing wrong here?

Thanks,
--
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