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    SubjectRe: [PATCH 2/3 v2] i2c: i801: enable irq for i801 smbus transactions
    On Tue, 19 Jun 2012 20:47:04 +0200, Jean Delvare wrote:
    > On Fri, 6 Jan 2012 18:58:21 +0800, Daniel Kurtz wrote:
    > > @@ -879,8 +953,24 @@ static int __devinit i801_probe(struct pci_dev *dev,
    > > i801_probe_optional_slaves(priv);
    > >
    > > pci_set_drvdata(dev, priv);
    > > +
    > > + if (priv->features & FEATURE_IRQ) {
    > > + init_waitqueue_head(&priv->waitq);
    > > + spin_lock_init(&priv->lock);
    > > +
    > > + err = request_irq(dev->irq, i801_isr, IRQF_SHARED,
    > > + i801_driver.name, priv);
    > > + if (err) {
    > > + dev_err(&dev->dev, "Failed to allocate irq %d: %d",
    >
    > Missing "\n".
    >
    > > + dev->irq, err);
    > > + goto exit_del_adapter;
    > > + }
    >
    > I believe order is wrong, and interrupt handler should be installed
    > _before_ registering the adapter. Otherwise you have a race condition
    > where the handler could be called before the waitqueue and spinlock are
    > initialized.

    Oh, and it's not a theoretical thing. I can reproducibly crash the
    kernel by removing and loading the i2c-i801 driver again. Swapping
    request_irq() and i2c_add_adapter() solves it.

    --
    Jean Delvare


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