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

H. Peter Anvin
2014-01-20T08:57:43Z

On 01/20/2014 12:26 AM, Peter Zijlstra wrote:
> 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).
>

The difference is the STI!

-hpa