Subject: Re: linux-next: build failure after merge of the tip tree

From: Peter Zijlstra <[email-masked]>
Date: Mon, 20 Jan 2014 09:26:20 +0100

On Sun, Jan 19, 2014 at 11:45:43PM -0500, Len Brown wrote:
> +static void mwait_idle(void)
> +{
> +       mwait_idle_with_hints(0, 0);
> +}
> +
> 
> The reason the patch above will crash Core2 machines is because
> core2 machines don't support mwait_idle_with_hints().
> 
> The calling sequence for old and new MWAIT instructions is different.
> The former must be invoked with interrupts enabled,
> and the later can be invoked with interrupts disabled,
> which is a feature that Linux takes advantage of.

What old and new? They're the same byte sequence: 0x0f 0x01 0xc9

And your 'old' __sti_mwait(0,0) has the exact same arguments as
mwait_idle_with_hints(0,0).