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Date: Tue, 31 Jan 2012 11:58:55 +0000
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To: Linus Torvalds <torvalds@linux-foundation.org>
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Subject: Re: [PATCH] NVMe: Fix compilation on architecturs without
 readq/writeq
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>   u64 val;
>   val = readl(addr);
>   val |= readl(addr+4) << 32;
> 
> is well-defined and must read the low word first - both at the C level
> *and* at the CPU level. Anything else would be a bug in the
> architecture "readl()" implementation or the hardware.

That doesn't make the access atomic to hardware however as a true 64bit
readq/writeq would be ?

It seems to me the two are not quite the same semantically