Re: [PATCH 01/11] sched: Make NOHZ CFS bandwidth checks follow proxy donor

[John Stultz]

On Thu, Jul 16, 2026 at 6:22 AM Andrea Righi <arighi@xxxxxxxxxx> wrote:
>
> Proxy execution separates the scheduling context in rq->donor from the
> physical execution context in rq->curr. sched_can_stop_tick() checks the
> latter for CFS bandwidth constraints and only does so when nr_running is
> one.
>
> A retained proxy donor keeps both the donor and mutex owner queued. The
> check therefore misses a constrained FAIR donor and may stop the tick
> while its runtime still needs to be enforced.
>
> Check the selected donor instead and remove the nr_running restriction.
> The donor being a queued FAIR task is sufficient to require bandwidth
> accounting regardless of other runnable tasks.
>
> Fixes: af0c8b2bf67b ("sched: Split scheduler and execution contexts")
> Reported-by: Sashiko <sashiko-bot@xxxxxxxxxx>
> Link: https://lore.kernel.org/r/20260713164807.E5ED21F00A3A@xxxxxxxxxxxxxxx
> Signed-off-by: Andrea Righi <arighi@xxxxxxxxxx>

Acked-by: John Stultz <jstultz@xxxxxxxxxx>