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SubjectRe: [Alternative][PATCH] ACPI / PCI: Set root bridge ACPI handle in advance
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On Thursday, December 27, 2012 02:31:09 PM Rafael J. Wysocki wrote:
> On Thursday, December 27, 2012 01:47:22 PM Rafael J. Wysocki wrote:
> > On Wednesday, December 26, 2012 04:10:32 PM Yinghai Lu wrote:
> > > On Wed, Dec 26, 2012 at 2:36 PM, Rafael J. Wysocki <rjw@sisk.pl> wrote:
> > > > On Wednesday, December 26, 2012 12:41:05 PM Yinghai Lu wrote:
> > > >> On Wed, Dec 26, 2012 at 12:16 PM, Yinghai Lu <yinghai@kernel.org> wrote:
> > > >> > On Wed, Dec 26, 2012 at 12:10 PM, Bjorn Helgaas <bhelgaas@google.com> wrote:
> > > >> >> Do you have a reference for this? I think this might have been true
> > > >> >> in the past, but I don't think it's true for any version of gcc we
> > > >> >> support for building Linux.
> > > >> >
> > > >> > http://lkml.indiana.edu/hypermail/linux/kernel/0804.3/3600.html
> > > >>
> > > >> the problem is already addressed by:
> > > >>
> > > >> | commit f9d14250071eda9972e4c9cea745a11185952114
> > > >> | Author: Linus Torvalds <torvalds@linux-foundation.org>
> > > >> | Date: Fri Jan 2 09:29:43 2009 -0800
> > > >> |
> > > >> | Disallow gcc versions 4.1.{0,1}
> > > >> |
> > > >> | These compiler versions are known to miscompile __weak functions and
> > > >> | thus generate kernels that don't necessarily work correctly. If a weak
> > > >> | function is int he same compilation unit as a caller, gcc may end up
> > > >> | inlining it, and thus binding the weak function too early.
> > > >> |
> > > >> | See
> > > >> |
> > > >> | http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27781
> > > >> |
> > > >> | for details.
> > > >>
> > > >> so it is ok to put the __weak in the same file now.
> > > >
> > > > Cool, thanks for checking and for the ACK!
> > >
> > > wait, we have some problem on systems that root bus is not exported via DSDT ...
> > >
> > > one of my nehalem system that have uncore cpu devices are not exported via ACPI.
> > >
> > > also there will be problem that system is booting with acpi=off.
> > >
> > >
> > > +int pcibios_root_bridge_prepare(struct pci_host_bridge *bridge)
> > > +{
> > > + struct pci_sysdata *sd = bridge->bus->sysdata;
> > > + struct pci_root_info *info = container_of(sd, struct pci_root_info, sd);
> > > +
> > > + ACPI_HANDLE_SET(&bridge->dev, info->bridge->handle);
> > > + return 0;
> > > +}
> > >
> > > will get wrong info...via sd... as their sd is standalone
> >
> > Yes, it will be called in all code paths leading to acpi_create_root_bus(),
> > not only the ones started by pci_acpi_scan_root(). Well, too bad.
>
> s/acpi_create_root_bus/pci_create_root_bus/
>
> Sorry.
>
> > By the way, that illustrates nicely why I generally have concerns about __weak
> > stuff and similar tricks.
> >
> > Bjorn, I had tried to use the approach you suggested, but it didn't work.
> > I thought about fixing that, but everything I could come up with turned out to
> > be too complicated, so I'm inclined to use the previous version after all:
> >
> > https://patchwork.kernel.org/patch/1889221/
> >
> > that has been acked by Yinghai, Greg and Peter already.

I think I know how to avoid the __weak thing without doing what the first
version did. I'll post a new version of the patch shortly.

Thanks,
Rafael


--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.


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