linux-kernel - Re: [GIT PATCH] driver core patches against 2.6.24

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Date:	Sat, 26 Jan 2008 15:50:57 +1100
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Greg KH <gregkh@...e.de>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [GIT PATCH] driver core patches against 2.6.24

On Saturday 26 January 2008 06:42:19 Greg KH wrote:
> On Fri, Jan 25, 2008 at 10:44:59AM -0800, Linus Torvalds wrote:
> > On Thu, 24 Jan 2008, Greg KH wrote:
> > > Here are a pretty large number of kobject, documentation, and driver
> > > core patches against your 2.6.24 git tree.
> >
> > I've merged it all, but it causes lots of scary warnings:
> >
> >  - from the purely broken ones:
> >
> > 	ehci_hcd: no version for "struct_module" found: kernel tainted.
>
> Ok, in looking at the code, this should also be showing up for you on a
> "clean" 2.6.24 release, I didn't change anything in this code path.
>
> That is what taints your kernel with the "F" flag.
>
> >  - to the scary ones:
> >
> > 	sysfs: duplicate filename 'ehci_hcd' can not be created
> > 	WARNING: at fs/sysfs/dir.c:424 sysfs_add_one()
> > 	Pid: 610, comm: insmod Tainted: GF       2.6.24-gb47711bf #28
> >
> > 	Call Trace:
> > 	 [<ffffffff802bd63c>] sysfs_add_one+0x54/0xbd
> > 	 [<ffffffff802bdbc0>] create_dir+0x4f/0x87
> > 	 [<ffffffff802bdc2d>] sysfs_create_dir+0x35/0x4a
> > 	 [<ffffffff803154c8>] kobject_get+0x12/0x17
> > 	 [<ffffffff80315607>] kobject_add_internal+0xd9/0x194
> > 	 [<ffffffff8031579c>] kobject_add_varg+0x54/0x61
> > 	 [<ffffffff80261efe>] __alloc_pages+0x66/0x2ee
> > 	 [<ffffffff80315321>] kobject_init+0x42/0x82
> > 	 [<ffffffff80315843>] kobject_init_and_add+0x9a/0xa7
> > 	 [<ffffffff802722c0>] __vmalloc_area_node+0x111/0x135
> > 	 [<ffffffff8025546b>] mod_sysfs_init+0x6e/0x83
> > 	 [<ffffffff802561e8>] sys_init_module+0xa3d/0x1833
> > 	 [<ffffffff8028ebd5>] dput+0x1c/0x10b
> > 	 [<ffffffff8020b3be>] system_call+0x7e/0x83
>
> This is the sysfs core telling you that someone did something stupid :)
>
> Yes, that's new, but the "error" was always there, I just made the
> warning more visible to get people to pay attention to it, and find the
> real errors where this happens (and it has found them, which is a good
> thing.)
>
> But in this case, it doesn't look like the module loading code will
> detect that we are trying to load a module that is already present until
> the kobjects are set up here.  It's been this way for a long time :(
>
> Rusty, any ideas of us adding a different check for "duplicate" modules
> like this earlier in the load_module() function, so we don't spend so
> much effort in building everything up when we don't need to?

module.c:1832 (in load_module)

	if (find_module(mod->name)) {
		err = -EEXIST;
		goto free_mod;
	}

That's pretty early, and before this backtrace.

Even for simultaneous loads, there's a mutex which protects from here to the 
list insertion.

Puzzled,
Rusty.
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