Re: pci: kernel crash in bus_find_device

[Guenter Roeck]

On 05/22/2014 12:14 AM, Greg Kroah-Hartmann wrote:
> On Wed, May 21, 2014 at 03:59:58PM -0700, Guenter Roeck wrote:
> > On Wed, May 21, 2014 at 01:04:04PM -0700, Francesco Ruggeri wrote:
> > > I have been using an x86 platform.
> > > When I started working on it I got early crashes until I added the
> > > check for p not NULL in
> > >
> > > +void bus_release_device(struct device *dev)
> > > +{
> > > + struct device_private *p = dev->p;
> > > +
> > > + if (p && klist_node_attached(&p->knode_bus))
> > > + klist_put_last(&p->knode_bus);
> > > +}
> > > +
> > >
> > > Maybe on powerpc *p is overriden between device_del and device_release?
> > >
> > > Or maybe some of the BUG_ONs in the patch? The ones on knode_dead are
> > > treated as WARN_ONs in the current klist code.
> > > The one in BUG_ON(!klist_dec_and_del(n)); is new, and in my tests I
> > > ran into it without the second patch (but only when I ran my module
> > > and tests).
> > Hi Francesco,
> >
> > I replaced the BUG_ON with WARN_ON; still crashes.
> >
> > Anyway, the problem seems to be known. I found two related exchanges.
> >
> > [1] describes pretty much the same problem. I don't see if/where it was
> > ever fixed, though.
> >
> > [2] is a patch to fix the problem. It did not apply cleanly to 3.14,
> > so I had to make some adjustments in klist_iter_init_node. Resulting
> > patch is below. With this patch, the problem is gone. It is not perfect,
> > as it aborts the loop if it encounters a deleted kobject, but it is better
> > than nothing. Unfortunately, the patch never made it upstream; no idea why.
> > Copying the author and Greg to get additional feedback.
> >
> > Guenter
> >
> > [1] https://lkml.org/lkml/2008/10/26/79
> > [2] https://lkml.org/lkml/2012/4/16/218
>
> 2 years ago?  I have no idea what was up with that, sorry...

Ok, but do you have comments on the patch itself in its current version ?

Guenter

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