Re: [broken-out-2007-07-20-00-22] kernel bug at kernel/params:570

Randy Dunlap
2007-07-20T23:34:05Z

On Fri, 20 Jul 2007 16:10:52 -0700 Greg KH wrote:

> On Fri, Jul 20, 2007 at 03:59:12PM -0700, Andrew Morton wrote:
> > On Fri, 20 Jul 2007 15:50:47 -0700
> > Greg KH <gregkh@suse.de> wrote:
> >
> > > On Fri, Jul 20, 2007 at 06:32:21PM +0200, Michal Piotrowski wrote:
> > > > Hi Greg,
> > > >
> > > > This looks like a sysfs bug
> > > > http://www.stardust.webpages.pl/files/tbf/bitis-gabonica/broken-out-2007-07-20-00-22/00003.jpg
> > > >
> > > > l *kernel_param_sysfs_setup+0x75
> > > > 0xc13c0894 is in kernel_param_sysfs_setup (kernel/params.c:570).
> > > > 565 mk->mod = THIS_MODULE;
> > > > 566 kobj_set_kset_s(mk, module_subsys);
> > > > 567 kobject_set_name(&mk->kobj, name);
> > > > 568 kobject_init(&mk->kobj);
> > > > 569 ret = kobject_add(&mk->kobj);
> > > > 570 BUG_ON(ret < 0);
> > > > 571 param_sysfs_setup(mk, kparam, num_params, name_skip);
> > > > 572 kobject_uevent(&mk->kobj, KOBJ_ADD);
> > > > 573 }
> > > > 574
> > > >
> > > > http://www.stardust.webpages.pl/files/tbf/bitis-gabonica/broken-out-2007-07-20-00-22/mm-config
> > >
> > > What kernel version is this happening on? The -mm tree? Can you try
> > > Linus's tree instead?
> > >
> > > It looks like there was some needed information right before the first
> > > stack dump, showing exactly what kobject was trying to be added that was
> > > already present. Odds are this is a kernel parameter with the same name
> > > as a duplicate one within the same module, but the trick is going to be
> > > trying to figure out what module is causing this.
> > >
> > > So it's not a sysfs bug, but rather a driver issue that this is
> > > catching.
> >
> > In that case a BUG was way too harsh treatment, and in fact directly
> > contributed to our inability to debug the bug!
> >
> > Can we wind that back a bit? Add some useful printks and then recover
> > in some fashion?
>
> Sure, I don't mind doing that at all.
>
> Hm, it looks like Randy added this back in September last year with:
> commit d8c7649e99e4b081b624aefe1e77caa30b53cb18
> Author: Randy Dunlap <rdunlap@xenotime.net>
> Date: Fri Sep 29 01:58:55 2006 -0700
>
> [PATCH] kernel/params: driver layer error checking
>
> Check driver layer return values in kernel/params.c
>
> Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
> Signed-off-by: Andrew Morton <akpm@osdl.org>
> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
>
> (wow, I love git and the signed-off-tree for things like this, it's
> trivial to find this information out.)
>
> So I'm guessing he was trying to catch something specific here.
>
> Randy, any objection to changing that BUG_ON to a printk warning instead
> telling the user exactly what needs to be fixed and that the system is
> now going to be unstable when any module is unloaded?

Of course not (no objection).

I added a BUG_ON() ? Shame on me.

---
~Randy
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