Messages in this thread | | | Date | Thu, 22 May 2014 10:57:00 -0700 | From | Guenter Roeck <> | Subject | Re: pci: kernel crash in bus_find_device |
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On Thu, May 22, 2014 at 09:19:40AM -0700, Francesco Ruggeri wrote: > Aborting a search does not sound like a correct solution. > How does a higher level user (eg for_each_pci_dev) know that a search > was aborted and decide whether it should try again, assuming it would > be ok repeating the action on the devices visited the first time? > Agreed, it is less than desirable.
I would consider this to be a secondary problem, though, the immediate problem being the crash. One possible solution might be to have the various functions return error codes (ERR_PTR), but that would be quite invasive as well. I really think we need input from Greg and, if the solution touches the PCI subsystem, from Bjorn Helgaas to find an acceptable solution to that problem.
Guenter
> Francesco > > > On Thu, May 22, 2014 at 12:22 AM, Guenter Roeck <linux@roeck-us.net> wrote: > > 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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