[Xen-devel] Re: [PATCH 13/14] x86/ticketlock: add slowpath logic

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

On 11/17/2010 12:58 AM, Avi Kivity wrote:
>> Actually in this case I'm pretty sure there's already a "set bit"
>> function which will do the job.  set_bit(), I guess, though it takes a
>> bit number rather than a mask...
>>
>
>
> set_bit() operates on a long, while the intel manuals recommend
> against operating on operands of different size, especially with
> locked operations.  I think newer processors have more relaxed
> requirements, though.

Despite its prototype, set_bit() is pretty specifically using "orb" for
a the constant case, or bts otherwise (I don't know what size memory
operation bts is considered to generate).

    J


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