Re: [PATCH] memcg: remove unneeded preempt_disable

James Bottomley
2011-08-25T18:34:44Z

Christoph Lameter <cl@linux.com> wrote:

>On Thu, 25 Aug 2011, James Bottomley wrote:
>
>> >ARM seems to have these LDREX/STREX instructions for that purpose
>which
>> >seem to be used for generating atomic instructions without lockes. I
>> >guess
>> >other RISC architectures have similar means of doing it?
>>
>> Arm isn't really risc. Most don't. However even with ldrex/strex
>you need two instructions for rmw.
>
>Well then what is "really risc"? RISC is an old beaten down marketing
>term
>AFAICT and ARM claims it too.

Reduced Instruction Set Computer. This is why we're unlikely to have complex atomic instructions: the principle of risc is that you build them up from basic ones.

James
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