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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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