Re: [PATCH v5 05/29] sched/deadline: Do not divide by zero active CPUs of a root domain

[Mathieu Desnoyers]

On 2026-11-09 09:30, Juri Lelli wrote:
[...]
> This 2nd hunk complements and tightens 4043f54984161 ("sched/deadline:
> Reject debugfs dl_server writes for offline CPUs") which has Fixes:
> d741f297bcea ("sched/fair: Fair server interface"). Do we need both
> fixes (if that is allowed) or maybe we need to split this change in two
> (as this second part won't apply to old kernels w/o dl-servers)?

Good point. I will split it in two in the next version:

- __dl_sub() and __dl_add() skip the division when the root domain has
  no active CPU. Fixes: daec57983670. This alone removes the divide
  error, on the debugfs path too.
- The debugfs write is refused while the runqueue is offline. Fixes:
  4043f5498416, which it completes for the hotplug windows. It only
  applies where that commit is.

Thanks,

Mathieu

--
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com