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

[Paul E. McKenney]

On Tue, Oct 22, 2024 at 12:13:12AM -0700, Christoph Hellwig wrote:
> On Tue, Oct 22, 2024 at 09:10:18AM +0200, Peter Zijlstra wrote:
> > Ah, well, the thing that got us here is that we (Andrii and me) wanted
> > to use -1 as an 'invalid' value to indicate SRCU is not currently in
> > use.
> > 
> > So it all being int is really rather convenient :-)
> 
> Then please document that use.  Maybe even with a symolic name for
> -1 that clearly describes these uses.

Would this work?

#define SRCU_INVALID_INDEX -1

Whatever the name, maybe Peter and Andrii define this under #ifndef
right now, and we get it into include/linux/srcu.h over time.

Or is there a better way?  Or name, for that matter.

							Thanx, Paul