linux-kernel - Re: 2.6.24-rc5 sysfs pci bridge duplicate symlink

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Message-ID: <20080110035503.GG20448@suse.de>
Date:	Wed, 9 Jan 2008 19:55:03 -0800
From:	Greg KH <gregkh@...e.de>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Bahadir Balban <bahadir.balban@...il.com>,
	linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.arm.linux.org.uk
Subject: Re: 2.6.24-rc5 sysfs pci bridge duplicate symlink

On Fri, Dec 28, 2007 at 11:50:49PM +0000, Russell King - ARM Linux wrote:
> On Fri, Dec 28, 2007 at 03:03:22PM -0800, Andrew Morton wrote:
> > On Fri, 28 Dec 2007 13:11:37 +0000 "Bahadir Balban" <bahadir.balban@...il.com> wrote:
> > 
> > > Hi,
> > > 
> > > On ARM with PCI, I get this error since -rc2 (didn't try rc1):
> > > 
> > > sysfs: duplicate filename 'bridge' can not be created
> > > WARNING: at fs/sysfs/dir.c:424 sysfs_add_one()
> > > [<c00287fc>] (dump_stack+0x0/0x14) from [<c00cbc64>] (sysfs_add_one+0x50/0xf4)
> > > [<c00cbc14>] (sysfs_add_one+0x0/0xf4) from [<c00ccd30>]
> > > (sysfs_create_link+0xec/0x184)
> > >  r6:cfca8b48 r5:cfca96c8 r4:cfc2fec0
> > > [<c00ccc44>] (sysfs_create_link+0x0/0x184) from [<c0160b44>]
> > > (pci_bus_add_devices+0xf0/0x144)
> > >  r7:cfc5a2d4 r6:cfc5a2d4 r5:cfc5a2c0 r4:cfcad800
> > > [<c0160a54>] (pci_bus_add_devices+0x0/0x144) from [<c0160b30>]
> > > (pci_bus_add_devices+0xdc/0x144)
> > >  r7:cfc5a3d4 r6:cfc5a3d4 r5:cfc5a3c0 r4:cfcadc00
> > > [<c0160a54>] (pci_bus_add_devices+0x0/0x144) from [<c0160b30>]
> > > (pci_bus_add_devices+0xdc/0x144)
> > >  r7:cfc5a4d4 r6:cfc5a4d4 r5:cfc5a4c0 r4:cfc5d400
> > > [<c0160a54>] (pci_bus_add_devices+0x0/0x144) from [<c000a934>]
> > > (pci_common_init+0x148/0x184)
> > >  r7:c035fd58 r6:cfc3e760 r5:c001e030 r4:cfc5a4c0
> > > 
> > > 
> > > Any idea why?
> > > 
> > 
> > (suitable cc added)
> 
> Looks to me as if the code added to pci_bus_add_devices() is off it's
> rocker.
> 
> In brief, pci_bus_add_devices() is supposed to be callable given *any*
> state of the bus, and it will add any new devices found in the bus tree
> from the bus that it's called for downwards.  (That's how I designed
> that bit of PCI code - so it can cope with hotpluggable PCI bridges.)
> 
> It still does this.  However, some bright spark decided to add sysfs
> links to it - and break it.  Now, whenever we descend into a subordinate
> bus (and return to a higher level) we will try to create a sysfs symlink
> even if the bus is one that we already registered.
> 
> So... that sysfs_create_link() call in there should not be unconditional.
> It should _only_ ever do that call if list_empty(&dev->subordinate->node)
> was true.  IOW, we only create symlinks for subordinate bus that we don't
> already know about.
> 
> It looks like it was introduced by Greg's "PCI: fix __must_check warnings"
> but why a patch advertised _solely_ as a fix is adding additional sysfs
> attributes I've no idea.

I'm sorry, but I don't see where that patch added new sysfs attributes
to anything.  It just reports any errors that might have occured and
hopefully properly handle them.  Did I mess up somewhere with this?

> Something like the following should fix it.  Bahadir - please test.

Any test results?

thanks,

greg k-h
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