Re: Regression with commit f9cde5f in 2.6.30-gitX

Gary Hade
2009-06-24T15:56:54Z

On Wed, Jun 24, 2009 at 04:51:48PM +0200, Thomas Gleixner wrote:
> On Wed, 24 Jun 2009, Jaswinder Singh Rajput wrote:
> > Reported-by: Larry Finger <Larry.Finger@lwfinger.net>
> > Signed-off-by: Jaswinder Singh Rajput <jaswinderrajput@gmail.com>
> > ---
> > arch/x86/pci/acpi.c | 16 ++++++++++------
> > 1 files changed, 10 insertions(+), 6 deletions(-)
> >
> > diff --git a/arch/x86/pci/acpi.c b/arch/x86/pci/acpi.c
> > index 16c3fda..0bc015f 100644
> > --- a/arch/x86/pci/acpi.c
> > +++ b/arch/x86/pci/acpi.c
> > @@ -69,6 +69,9 @@ setup_resource(struct acpi_resource *acpi_res, void *data)
> > struct resource *root;
> > int max_root_bus_resources = PCI_BUS_NUM_RESOURCES;
> >
> > + if (info->res_num >= PCI_BUS_NUM_RESOURCES)
> > + return AE_OK;
> > +
> > status = resource_to_addr(acpi_res, &addr);
> > if (!ACPI_SUCCESS(status))
> > return AE_OK;
> > @@ -94,17 +97,18 @@ setup_resource(struct acpi_resource *acpi_res, void *data)
> > if (bus_has_transparent_bridge(info->bus))
> > max_root_bus_resources -= 3;
> > if (info->res_num >= max_root_bus_resources) {
> > - printk(KERN_WARNING "PCI: Failed to allocate 0x%lx-0x%lx "
> > - "from %s for %s due to _CRS returning more than "
> > - "%d resource descriptors\n", (unsigned long) res->start,
> > - (unsigned long) res->end, root->name, info->name,
> > - max_root_bus_resources);
> > + pr_warning("PCI: Failed to allocate 0x%lx-0x%lx "
> > + "from %s for %s due to _CRS returning more than "
> > + "%d resource descriptors\n",
> > + (unsigned long)res->start, (unsigned long)res->end,
> > + root->name, info->name, max_root_bus_resources);
>
> Can you please avoid mixing cleanup patches with bug fixes ? I almost
> did not see the line below.
>
> > + info->bus->resource[info->res_num] = res;
>
> Storing the resource in defeats the purpose of the original patch,
> which makes sure that we do _NOT_ use the last 3 slots of the resource
> array for a root bus with a transparent bridge.
>
> > info->res_num++;
>
> This is the real bug. info->res_num should not be incremented when we
> run out of resources already.

This probably isn't needed but I don't think it is the cause of
the problem. It is just counting the number of _CRS returned
resources and I believe subsequent visits to setup_resource()
for additional returned resources will generate the same warning
as it also would if the instruction were removed and no longer
being used to keep an accurate count.

I suspect that the resource array is simply not large enough
for that system (and possibly others) and will have to be made
larger by increasing PCI_BUS_NUM_RESOURCES.

Gary

--
Gary Hade
System x Enablement
IBM Linux Technology Center
503-578-4503 IBM T/L: 775-4503
garyhade@us.ibm.com