Re: [PATCH 3/3] sched/nohz: Remove weird error handling from find_new_ilb()

[Ingo Molnar]

* Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:

> On Fri, Oct 06, 2023 at 12:25:18PM +0200, Ingo Molnar wrote:
> > find_new_ilb() returns nr_cpu_ids on failure - which is a weird
> > choice in itself: not only is it a global variable, it is
> > a +1 out of bounds CPU index...
> 
> FWIW this is what all the cpumask bitops return when they've exhausted
> the mask. Eg. no bits left set etc..

yeah, which then results in type-forcing uglies like:

   kernel/events/core.c:	if ((unsigned)cpu >= nr_cpu_ids) {
   kernel/events/core.c:   if ((unsigned)cpu >= nr_cpu_ids) {
   kernel/smp.c:	   if ((unsigned)cpu >= nr_cpu_ids || !cpu_online(cpu)) {

:-/

So I don't think this is a particularly well thought-out interface.

Thanks,

	Ingo