Re: [PATCH 07/15] x86: add xadd helper macro

[H. Peter Anvin]

On 08/22/2011 04:43 PM, Jeremy Fitzhardinge wrote:
> On 08/22/2011 04:29 PM, H. Peter Anvin wrote:
>> On 08/22/2011 04:15 PM, Jeremy Fitzhardinge wrote:
>>> From: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
>>>
>>> Add a common xadd implementation.
>>>
>>> This has the side effect of generating a bad instruction if you try to
>>> use it on a 64-bit value on a 32-bit system - but don't do that.
>>>
>> It would be better to barf at that point, so we get the error with a C
>> line... also, there needs to be a default clause with
>> __compiletime_error() in it.
> 
> OK, but the "standard of care" here is the old "calling undefined
> function" link error; getting a bad asm instruction is a little more
> helpful, in a sense.  But agreed on the default: case.  I'll see if I
> can fix up xadd and cmpxchg to fail better as well.
> 

__compiletime_error() is better than either, obviously...

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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