Re: [linux-pm] Bug in PCI core

[Alan Stern <stern@rowland.harvard.edu>]

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

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/