Re: [PATCH v2] PCI: fix pci_bus_alloc_resource() hang, preferpositive decode

From: Jesse Barnes
Date: Fri Nov 12 2010 - 12:19:12 EST


On Wed, 10 Nov 2010 10:26:07 -0700
Bjorn Helgaas <bjorn.helgaas@xxxxxx> wrote:

>
> When a PCI bus has two resources with the same start/end, e.g.,
>
> pci_bus 0000:04: resource 2 [mem 0xd0000000-0xd7ffffff pref]
> pci_bus 0000:04: resource 7 [mem 0xd0000000-0xd7ffffff]
>
> the previous pci_bus_find_resource_prev() implementation would alternate
> between them forever:
>
> pci_bus_find_resource_prev(... [mem 0xd0000000-0xd7ffffff pref])
> returns [mem 0xd0000000-0xd7ffffff]
> pci_bus_find_resource_prev(... [mem 0xd0000000-0xd7ffffff])
> returns [mem 0xd0000000-0xd7ffffff pref]
> pci_bus_find_resource_prev(... [mem 0xd0000000-0xd7ffffff pref])
> returns [mem 0xd0000000-0xd7ffffff]
> ...
>
> This happened because there was no ordering between two resources with the
> same start and end. A resource that had the same start and end as the
> cursor, but was not itself the cursor, was considered to be before the
> cursor.
>
> This patch fixes the hang by making a fixed ordering between any two
> resources.
>
> In addition, it tries to allocate from positively decoded regions before
> using any subtractively decoded resources. This means we will use a
> positive decode region before a subtractive decode one, even if it means
> using a smaller address.
>
> Reference: https://bugzilla.kernel.org/show_bug.cgi?id=22062
> Reported-by: Borislav Petkov <bp@xxxxxxxxx>
> Signed-off-by: Bjorn Helgaas <bjorn.helgaas@xxxxxx>
> ---

Applied to my for-linus branch, thanks.

--
Jesse Barnes, Intel Open Source Technology Center
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