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SubjectRe: [PATCH 3/3] 64-bit futexes: x86 support


On Fri, 30 May 2008, Ulrich Drepper wrote:
>
> +#ifdef CONFIG_X86_32
> + /* Not all 32-bit machines support 8-byte cmpxchg. We just
> + unconditionally perform a runtime check for the feature. */
> + if ((op & FUTEX_FLAG_64) && !boot_cpu_has(X86_FEATURE_CX8))
> + return -ENOSYS;
> +#endif

Also, doesn't this mean that effectively you have given up on any CPU
before the Pentium entirely?

Not that I want to take the patches _anyway_, but it seems doubly stupid.
Those things are going to be UP machines, so you could have just emulated
it with no correctness issues by disabling preemption.

Linus


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