Re: [PATCH rcu] srcu: Guarantee non-negative return value from srcu_read_lock()

[Christoph Hellwig]

On Tue, Oct 22, 2024 at 10:29:13AM -0700, Andrii Nakryiko wrote:
> >
> > Would this work?
> >
> > #define SRCU_INVALID_INDEX -1
> >
> 
> But why?

Becaue it very clearly documents what is going on.

>It's a nice property to have an int-returning API where valid
> values are only >= 0, so callers are free to use the entire negative
> range (not just -1) for whatever they need to store in case there is
> no srcu_idx value.

Well, if you have a concrete use case for that we can probably live
with it, but I'd rather have that use case extremely well documented,
as it will be very puzzling to the reader.