Re: [PATCH v2 04/21] sched/deadline: Do not divide by zero active CPUs of a root domain

[Mathieu Desnoyers]

On 2026-11-04 16:46, sashiko-bot@xxxxxxxxxx wrote:
[...]
> [Severity: Medium]
> Can updating dl_b->total_bw when cpus == 0 (or on an inactive CPU) underflow
> or corrupt dl_b->total_bw in the paths mentioned in the commit message?

That write is refused in v3 while the CPU is inactive (patch 4). The inactive
timer path is closed by patches 10 and 14: a release after a rebuild takes
nothing, and otherwise comes from the root domain that counted the bandwidth.
With admission control off, sched_setattr() on a task asleep on an offline
CPU still counts in the default root domain, with no active CPU to spread
the change over; the guard is for that, and the record releases from the
same root domain.

Thanks,

Mathieu

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