linux-kernel - Re: threshold_init_device/kobject_uevent

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Date:	Fri, 25 Jan 2008 22:14:19 -0800
From:	Greg KH <gregkh@...e.de>
To:	Yinghai Lu <yhlu.kernel@...il.com>, jacob.shin@....com
Cc:	Ingo Molnar <mingo@...e.hu>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: threshold_init_device/kobject_uevent_env oops

On Fri, Jan 25, 2008 at 10:04:19PM -0800, Yinghai Lu wrote:
> On Jan 25, 2008 2:50 PM, Greg KH <gregkh@...e.de> wrote:
> > On Fri, Jan 25, 2008 at 02:47:11PM -0800, Greg KH wrote:
> > > On Fri, Jan 25, 2008 at 11:35:56PM +0100, Ingo Molnar wrote:
> > > >
> > > > * Greg KH <gregkh@...e.de> wrote:
> > > >
> > > > > On Fri, Jan 25, 2008 at 01:05:40PM -0800, Yinghai Lu wrote:
> > > > > > current linus tree + x86.git
> > > > > >
> > > > > > got
> > > > > >
> > > > > > Calling initcall 0xffffffff80b93d98: threshold_init_device+0x0/0x3f()
> > > > > > BUG: unable to handle kernel NULL pointer dereference at 0000000000000040
> > > > > > IP: [<ffffffff80458e20>] kobject_uevent_env+0x2a/0x3d9
> > > > >
> > > > > Does this happen on just Linus's tree?
> > > > >
> > > > > Can you send me a .config file for this?
> > > > >
> > > > > What is threshold_init()?  Is it something new in the x86.git tree?
> > > >
> > > > no. A quick grep shows that it is in a file that _your_ changes in
> > > > Linus' latest have touched:
> > > >
> > > >   arch/x86/kernel/cpu/mcheck/mce_amd_64.c
> > >
> > > Ok, those are pretty much just search/and/replace type changes, but I
> > > have been running x86-64 boxes with these changes in place.
> >
> > Oh wait, I do see a change.  We are now (finally) emitting a kobject
> > uevent for these devices, which somehow the code can't handle properly.
> >
> > Let me go poke this some more, unfortunatly I don't have any AMD 64
> > boxes here anymore, only Intel based processors, so I can't run this
> > module...
> 
> it only happens with AMD Quad Core CPU or Fam 10h.
> 
> works well with AMD opteron Rev E, and Rev F.

So this only dies on a multi-core system?  Or does 2 processor boxes
work, but not 4?

> So you may need have access to new system with quad core cpu.

Ugh, that's not good.

The kobjects here are really not making much sense.

Jacob, any hints on exactly what you were trying to do with these
kobjects?  What's the end goal here, and why didn't you just use a
struct device instead?

The mce_amd_64.c file is the only thing in the tree using this userspace
API, can you please document it in Documentation/ABI so that others can
understand what it is used for, what files are expected, and what values
in the files are?

thanks,

greg k-h
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