linux-kernel - Re: linux-next: manual merge of the driver-core tree with the net-next tree

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Message-ID: <54804861.2060407@broadcom.com>
Date:	Thu, 4 Dec 2014 12:41:21 +0100
From:	Arend van Spriel <arend@...adcom.com>
To:	Jeremiah Mahler <jmmahler@...il.com>,
	<linux-kernel@...r.kernel.org>,
	"Greg Kroah-Hartman" <gregkh@...uxfoundation.org>
Subject: Re: linux-next: manual merge of the driver-core tree with the net-next
 tree

On 04-12-14 11:19, Jeremiah Mahler wrote:
> Arend,
> 
> I haven't heard if you have looked at this bug at all yet.  I was
> curious so I looked at it some more and I have some more information
> that might be helpful.
> 
> On Wed, Dec 03, 2014 at 01:41:28PM -0800, Jeremiah Mahler wrote:
>> On Wed, Dec 03, 2014 at 01:06:59PM -0800, Jeremiah Mahler wrote:
>>> Arend,
>>>
> [...]
>>>>>
>>>>> I took a look at the patch that is causing this problem (d32394fae95).
>>>>> My config negates everything in the patch except for a one line change
>>>>> to ath9k/pci.c.  If I remove this change (shown below) the problem goes
>>>>> away.
>>>>
>>>> Ok. But then it will likely crash when you cat one of the changed debugfs
>>>> files. Guess this commit needs to be reverted entirely.
>>>>
> [...]
> 
> Referring to the code snippet below, notice that both pci_set_drvdata()
> and dev_set_drvdata() are called.  If the call to dev_set_drvdata() is
> removed the bug goes away.
> 
>   drivers/net/wireless/ath/ath9k/pci.c
> 
>   861     SET_IEEE80211_DEV(hw, &pdev->dev);
>   862     pci_set_drvdata(pdev, hw);
>   863
>   864     sc = hw->priv;
>   865     sc->hw = hw;
>   866     sc->dev = &pdev->dev;
>   867     dev_set_drvdata(sc->dev, sc);
>   868     sc->mem = pcim_iomap_table(pdev)[0];
>   869     sc->driver_data = id->driver_data;
> 
> Translating the call to pci_set_drvdata() produces the following.
> 
>   pci_set_drvdata(pdev, hw);
>     (translating from include/linux/pci.h)
>     dev_set_drvdata(&pdev->dev, hw)
>       (translating from include/linux/device.h)
>       &pdev->dev->driver = hw;
> 
> And doing the same for dev_set_drvdata().
> 
>   dev_set_drvdata(sc->dev, sc)
>     (sc->dev = &pdev->dev)
>     dev_set_drvdata(&pdev->dev, sc)
>       (translating from include/linux/device.h)
>       &pdev->dev->driver = sc;
> 
> The same destination is being set with two different values.  Then calls
> to pci_get_drvdata(), which expect hw, are getting sc, and it breaks.

Yes, that was my suspicion as well. This is why I asked to revert the
patch entirely. I see that sc equals hw->priv so I know how to correct
it. However, with merge window around the corner it may be easier to do
a revert.

Regards,
Arend
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