Messages in this thread |  | | | Date | Fri, 02 May 2008 17:42:58 -0700 | | From | "H. Peter Anvin" <> | | Subject | Re: HELP: Is writeq an atomic operation?? |
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Roland Dreier wrote: > > Is a 64bit write to MMIO registers an atomic operation when using the > > writeq API? > > > > My concern is when I send 64bit data via writeq, will it be sent out as > > two 32 bit writes? If so, is it possible that another CPU be sending > > the data at the same time. Meaning can I write the 1st 32bit data from > > CPU-A, meanwhile CPU-B is writing his 32bit data at the same time, and > > CPU-A didn't complete the full 64bit in one shot. If this could occur, > > is there an API that I can use to make sure the entire data sent in one > > atomic operation? > > 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.
-hpa
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