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    SubjectRe: [linux-pm] Bug in PCI core
    On Fri, 13 Oct 2006, Alan Cox wrote:

    > Ar Gwe, 2006-10-13 am 10:49 -0600, ysgrifennodd Matthew Wilcox:
    > > No it didn't. It's undefined behaviour to perform *any* PCI config
    > > access to the device while it's doing a D-state transition. It may have
    >
    > I think you missed the earlier parts of the story - the kernel caches
    > the base config register state.
    >
    > > happened to work with the chips you tried it with, but more likely you
    > > never hit that window because X simply didn't try to do that.
    >
    > Which is why the kernel caches the register state. This all came up long
    > ago and the solution we currently have was the one chosen after
    > considerable debate and analysis about things like locking. We preserved
    > the historical reliable interface going back to the early Linux PCI
    > support and used by all the apps.

    Would it be okay for pci_block_user_cfg_access() to use its own cache, so
    it doesn't interfere with data previously cached by pci_save_state()?

    Alan Stern

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