linux-kernel - Re: [PATCH 2/3 v2] i2c: i801: enable irq for i801 smbus transactions

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Date:	Wed, 20 Jun 2012 18:21:47 +0800
From:	Daniel Kurtz <djkurtz@...omium.org>
To:	Jean Delvare <khali@...ux-fr.org>
Cc:	ben-linux@...ff.org, seth.heasley@...el.com, ben@...adent.org.uk,
	David.Woodhouse@...el.com, linux-i2c@...r.kernel.org,
	linux-kernel@...r.kernel.org, olofj@...omium.org,
	bleung@...omium.org
Subject: Re: [PATCH 2/3 v2] i2c: i801: enable irq for i801 smbus transactions

On Wed, Jun 20, 2012 at 4:58 PM, Jean Delvare <khali@...ux-fr.org> wrote:
> 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,

Thanks for taking a look at these patches... and for testing them!
They were from more than 7 months ago, so it will take me a little
time to context switch back to the point where I can really digest
your feedback and update and test them again myself.  But, I wanted to
just let you know that I am reading your review comments, and will get
to it as soon as I can.
Speaking of which, I have only seen comments on patches 1 & 2 so far.
Any comments on patch 3?

-Daniel

>
> --
> Jean Delvare
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