Re: [PATCH 10/17] prmem: documentation

[Andy Lutomirski]

> On Oct 31, 2018, at 3:11 AM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> 
>> On Wed, Oct 31, 2018 at 12:15:46AM +0200, Igor Stoppa wrote:
>> On 30/10/2018 23:02, Andy Lutomirski wrote:
> 
>>> But I dislike allowing regular writes in the protected region. We
>>> really only need four write primitives:
>>> 
>>> 1. Just write one value.  Call at any time (except NMI).
>>> 
>>> 2. Just copy some bytes. Same as (1) but any number of bytes.
>>> 
>>> 3,4: Same as 1 and 2 but must be called inside a special rare write
>>> region. This is purely an optimization.
>> 
>> Atomic? RCU?
> 
> RCU can be done, that's not really a problem. Atomics otoh are a
> problem. Having pointers makes them just work.
> 
> Andy; I understand your reason for not wanting them, but I really don't
> want to duplicate everything. Is there something we can do with static
> analysis to make you more comfortable with the pointer thing?

Iâm sure we could do something with static analysis, but I think seeing a real use case where all this fanciness makes sense would be good.

And I donât know if s390 *can* have an efficient implementation that uses pointers. OTOH they have all kinds of magic stuff, so who knows?