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

From: Jeremiah Mahler
Date: Thu Dec 04 2014 - 05:19:29 EST


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.


861 SET_IEEE80211_DEV(hw, &pdev->dev);
862 pci_set_drvdata(pdev, hw);
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.

- Jeremiah Mahler
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