Re: [PATCH 0/3] sched: Fix proxy-exec use of curr and donor

[Hui Su]

> Yes. My first patch and Hui's v5 2/4 and 3/4 move the NUMA and cache
> ticks onto rq->curr when that task is fair. Hui's 1/4 is the right
> shape: task_tick() runs the donor class and, when a proxy crosses
> classes, the execution class as well. A fair lock holder whose donor
> is RT or deadline still gets those hooks. My patch only changes
> task_tick_fair(), so that case stays missing. I'll drop it.

Thanks Jemmy,

Yes, agreed on 1/3.

For 2/3, I think this also overlaps with an earlier standalone patch I
posted on Sep 2:

[PATCH] sched/core: fix task_sched_runtime() for proxy execution
Message-ID: <20260902112539.879979-1-sh_def@xxxxxxx>
https://lore.kernel.org/r/20260902112539.879979-1-sh_def@xxxxxxx/

It makes the same two changes in task_sched_runtime(): test whether @p is
the execution context with task_current(), while still invoking
update_curr() through rq->donor->sched_class.

For 3/3, Andrea has an earlier patch, first posted on Jul 16, addressing
the same NOHZ CFS bandwidth issue:

sched: Make NOHZ CFS bandwidth checks follow proxy donor
https://lore.kernel.org/r/20260716132229.61603-2-arighi@xxxxxxxxxx/

In particular, that patch also removes the nr_running == 1 restriction.
As Andrea points out, a retained proxy donor keeps both the donor and
mutex owner queued, so keeping that restriction would skip the bandwidth
check in the active proxy case.

Thanks,
Hui