Re: pci: kernel crash in bus_find_device

[Greg Kroah-Hartmann <gregkh@linuxfoundation.org>]

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...

greg k-h