On Fri, Aug 18, 2017 at 11:10 PM, Linus Torvalds
<torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
> On Fri, Aug 18, 2017 at 1:59 PM, Luc Van Oostenryck wrote:
>>
>> Yes, I see potential too, but nothing very specific. Have you something in mind?
>
> No, to a first approximation I'd just continue to add and subtract
> constant values.
>
> But it might allow us to do conditional contexts, which the kernel
> actually needs. Right now the kernel does tricks like this:
>
> # define __cond_lock(x,c) ((c) ? ({ __acquire(x); 1; }) : 0)
>
> (see include/linux/compiler.h) exactly because we want to not really
> add a constant 1 to the context, but add it only if the condition "c"
> was non-zero.
Yes, it could be like __context_{set,clr}(x, <boolean>)
or even __context_{or, xor, and, clr}(x, <somebitmask>)
> We then depend on sparse just doing the flow simplification etc. But
> it *could* have been done by just instead allowing the context to be
> updated with a boolean variable..
>
> But sparse might prefer that flow-based approach anyway - I'm just
> saying that sometimes a more flexible model could be a good thing at
> least in theory.
Absolutetly.
-- Luc
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