linux-kernel - Re: [PATCH] PCI: kirin: Fix section mismatch warning

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Message-ID: <20180919175849.GA8787@flashbox>
Date:   Wed, 19 Sep 2018 10:58:49 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     lorenzo.pieralisi@....com, songxiaowei@...ilicon.com,
        wangbinghui@...ilicon.com, bhelgaas@...gle.com,
        linux-pci@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        Greg KH <gregkh@...uxfoundation.org>
Subject: Re: [PATCH] PCI: kirin: Fix section mismatch warning

On Wed, Sep 19, 2018 at 10:35:55AM -0700, Nick Desaulniers wrote:
> On Wed, Sep 19, 2018 at 3:29 AM Lorenzo Pieralisi
> <lorenzo.pieralisi@....com> wrote:
> >
> > Xiaowei, Binghui,
> >
> > On Tue, Sep 18, 2018 at 10:38:29PM -0700, Nathan Chancellor wrote:
> > > WARNING: vmlinux.o(.text+0x4758cc): Section mismatch in reference from
> > > the function kirin_pcie_probe() to the function
> > > .init.text:kirin_add_pcie_port()
> > > The function kirin_pcie_probe() references
> > > the function __init kirin_add_pcie_port().
> > > This is often because kirin_pcie_probe lacks a __init
> > > annotation or the annotation of kirin_add_pcie_port is wrong.
> > >
> > > Remove '__init' from kirin_add_pcie_port so there is no mismatch.
> >
> > I think that instead of removing __init section tag we should add
> > it to kirin_pcie_probe().
> 
> A bunch of these functions have a single call site, with a mix of __init:
> 
> kirin_pcie_probe() ->
>   kirin_add_pcie_port() ->  // __init
>     kirin_pcie_add_msi()
> 
> But it looks like probe functions should be marked init:
> $ cd drivers; grep -r __init | grep probe
> 
> seems to turn up quite a lot of *probe() functions that are marked __init.
> https://www.tldp.org/LDP/lkmpg/2.4/html/x281.htm has more info, and
> from reading that, it seems that it's a no-op for a module that's
> marked loadable.
> 
> So I agree; __init should be added to kirin_pcie_probe(), but also
> kirin_pcie_add_msi().  That way if the module is statically compiled
> into the kernel image, these functions with a single call site get
> cleaned up after init.
> 
> Nathan, would you mind sending a v2?
> 

Hi Nick and Lorenzo,

I had tested adding __init to both kirin_pcie_probe and
kirin_pcie_add_msi but ran into this warning:

WARNING: vmlinux.o(.data+0x68b78): Section mismatch in reference from
the variable kirin_pcie_driver to the function
.init.text:kirin_pcie_probe()
The variable kirin_pcie_driver references                      
the function __init kirin_pcie_probe()

Doing a quick 'grep -r __init | grep platform_driver' doesn't show any
'static struct platform_driver' constructs marked as __init, leading me
to believe this patch is the proper solution.

I'm happy to hear otherwise, thank you both for the quick responses,
Nathan

> >
> > Please let me know and ACK accordingly.
> >
> > Lorenzo
> >
> > > Fixes: fc5165db245a ("PCI: kirin: Add HiSilicon Kirin SoC PCIe controller driver")
> > > Reported-by: Nick Desaulniers <ndesaulniers@...gle.com>
> > > Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
> > > ---
> > >  drivers/pci/controller/dwc/pcie-kirin.c | 4 ++--
> > >  1 file changed, 2 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/pci/controller/dwc/pcie-kirin.c b/drivers/pci/controller/dwc/pcie-kirin.c
> > > index 5352e0c3be82..9b599296205d 100644
> > > --- a/drivers/pci/controller/dwc/pcie-kirin.c
> > > +++ b/drivers/pci/controller/dwc/pcie-kirin.c
> > > @@ -467,8 +467,8 @@ static int kirin_pcie_add_msi(struct dw_pcie *pci,
> > >       return 0;
> > >  }
> > >
> > > -static int __init kirin_add_pcie_port(struct dw_pcie *pci,
> > > -                                   struct platform_device *pdev)
> > > +static int kirin_add_pcie_port(struct dw_pcie *pci,
> > > +                            struct platform_device *pdev)
> > >  {
> > >       int ret;
> > >
> > > --
> > > 2.19.0
> > >
> 
> 
> 
> -- 
> Thanks,
> ~Nick Desaulniers