Re: [git pull] PCI changes for 2.6.30

From: Alex Chiang <achiang@hp.com>
To: Sam Ravnborg <sam@ravnborg.org>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org
Subject: Re: [git pull] PCI changes for 2.6.30
Date: Wed, 1 Apr 2009 16:23:10 -0600	[thread overview]
Message-ID: <20090401222310.GA31290@ldl.fc.hp.com> (raw)
In-Reply-To: <20090401191220.GB29673@uranus.ravnborg.org>

* Sam Ravnborg <sam@ravnborg.org>:
> On Wed, Apr 01, 2009 at 12:37:49PM -0600, Alex Chiang wrote:
> > * Jesse Barnes <jbarnes@virtuousgeek.org>:
> > > On Wed, 1 Apr 2009 10:01:12 -0700 (PDT)
> > > Linus Torvalds <torvalds@linux-foundation.org> wrote:
> > > > On Tue, 31 Mar 2009, Jesse Barnes wrote:
> > > > >
> > > > > Please consider pulling my PCI tree from
> > > > >   git://git.kernel.org/pub/scm/linux/kernel/git/jbarnes/pci-2.6
> > > > > linux-next
> > > > 
> > > > This produces
> > > > 
> > > >   WARNING: drivers/built-in.o(.text+0x69a1): Section mismatch in
> > > > reference from the function dev_rescan_store() to the
> > > > function .devinit.text:pci_rescan_bus() The function
> > > > dev_rescan_store() references the function __devinit
> > > > pci_rescan_bus(). This is often because dev_rescan_store lacks a
> > > > __devinit annotation or the annotation of pci_rescan_bus is wrong.
> > > > 
> > > > Hmm?
> > > 
> > > Arg how did I miss that?  Maybe the last build I did was missing
> > > hotplug support or something... Anyway looking now (at first glance I
> > > think pci_rescan_bus needs to drop __devinit).
> > 
> > This was my fault. pci_rescan_bus() definitely does not want
> > __devinit.
> > 
> > But I'm confused -- didn't we used to have an option in
> > menuconfig under Kernel Hacking that would turn on section
> > mismatch warnings? I used to have that turned on, and don't
> > remember turning it off, and I can't find it now.
> > 
> > I'm told that we're supposed to set it on the make command line,
> > like:
> > 
> > 	make CONFIG_DEBUG_SECTION_MISMATCH=y -j16
> > 
> > or something. Has this changed recently or am I just imagining
> > things (or just plain stupid?)
> 
> That was maybe one year ago we had it in menuconfig.
> When I get on top of things I will enable it and try to
> help fixing the remaining warnings.

Ah, ok.

> I have resisted enabling it for now as I cannot support the people
> that see the warnings atm.

Nod, makes sense.

I took a look at the warning that Linus mentioned, and I'm not
entirely sure how to fix it. The problem is this:

http://git.kernel.org/?p=linux/kernel/git/jbarnes/pci-2.6.git;a=commit;h=3ed4fd96b3188406ac5357d9290bcffa08c65cf6

I initially annoted pci_rescan_bus as __devinit, which it
shouldn't have. Removing the annotation though, produces these
other warnings:

WARNING: vmlinux.o(.text+0x1b9be6): Section mismatch in reference from the function pci_rescan_bus() to the function .devinit.text:pci_scan_child_bus()
The function pci_rescan_bus() references
the function __devinit pci_scan_child_bus().
This is often because pci_rescan_bus lacks a __devinit 
annotation or the annotation of pci_scan_child_bus is wrong.

Reading through Documentation/PCI/pci.txt says that under
CONFIG_HOTPLUG, __devinit should be a nop?

I do have this in my .config:

CONFIG_HOTPLUG=y

So I'm not sure what I'm doing wrong?

Thanks.

/ac