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Subject: Re: [OMPI devel] [PATCH] Open MPI on ARMv5
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2012-04-30 16:19:30


I'm good with it as long as you guys are.

Re the "...for now" comment; does this imply that you're going to do more later?

BTW, I assume this is for trunk and the v1.6 branch, right?

On Apr 30, 2012, at 9:47 AM, Leif Lindholm wrote:

> Thanks,
>
> I'm happy for this to go in - Jeff?
>
> /
> Leif
>
>> -----Original Message-----
>> From: nave.notnilc_at_[hidden] [mailto:nave.notnilc_at_[hidden]] On Behalf
>> Of Evan Clinton
>> Sent: 30 April 2012 05:12
>> To: Leif Lindholm
>> Cc: Open MPI Developers; Jeffrey Squyres
>> Subject: Re: [OMPI devel] [PATCH] Open MPI on ARMv5
>>
>> Thanks again for the comments.
>>
>>>> Quote the documentation, __kuser_cmpxchg "already includes memory
>>>> barriers as needed," so the code using it shouldn't need anything
>>>> extra.
>>>
>>> Fair enough - but could you put a comment to this effect into the
>> patch?
>> Comment added.
>>
>>> But I'm still not too happy about even the very unlikely risk of
>>> something executing "random stuff" depending on kernel version.
>>> For now, could you update the comments to that effect that:
>>>
>>> "These kernel functions are available on kernel versions 2.6.15 and
>>> greater" + ", and running this software on earlier versions will
>> result
>>> in undefined behaviour."
>> Comment added.
>>
>>> What I'm suggesting is not to parse information out of the build
>> host,
>>> but rather using the configured toolchain and options and try to
>>> assemble the 64-bit atomic instructions. This would make it easy to
>>> rebuild a generic ARMv6 package to support 64-bit atomics by just
>> adding
>>> -march=armv6zk to CFLAGS.
>> Ah, I get it. I may see if I can come up with a nice test in the near
>> future.
>>
>> For now, revised patch attached.
>
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-- 
Jeff Squyres
jsquyres_at_[hidden]
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