Re: [patch] mm: fix PageUptodate memory ordering bug

[Andrew Morton <akpm@linux-foundation.org>]

On Sun, 23 Dec 2007 10:14:05 +0100 Nick Piggin <npiggin@suse.de> wrote:

>  config X86_PPRO_FENCE
> -	bool
> +	bool "PentiumPro memory ordering errata workaround"
>  	depends on M686 || M586MMX || M586TSC || M586 || M486 || M386 || MGEODEGX1
> -	default y
> +	default n
> +	help
> +	  Old PentiumPro multiprocessor systems had errata that could cause memory
> +	  operations to violate the x86 ordering standard in rare cases. Enabling this
> +	  option will attempt to work around some (but not all) occurances of
> +	  this problem, at the cost of much heavier spinlock and memory barrier
> +	  operations.
> +
> +	  If unsure, say n here. Even distro kernels should think twice before enabling
> +	  this: there are few systems, and an unlikely bug.
>  

I think if we're going to do this then we should add a runtime check for the
offending CPU then do panic("your kernel config ain't right").

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