Re: HELP: Is writeq an atomic operation??

H. Peter Anvin
2008-05-03T17:41:21Z

Alan Cox wrote:
>>> I don't have an authoritative answer, but I can say that I coded
>>> drivers/infiniband/hw/mthca and .../mlx4 assuming that writeq() is
>>> atomic in the sense that you say, and no one has reported any problems.
>>>
>> If you're not under lock you're screwed on a 32-bit platform.
>
> So what cycles does an MMX, SSE or double float store generate on the
> bus ?
>

Those do generate 64-bit stores; it's just *really* expensive to do it
in the kernel. I have used that trick to test 64-bit hardware in a
32-bit only system, though.

-hpa