Re: [PATCH] sched/core: Account PSI IRQ time to the execution context

[Peter Zijlstra <peterz@infradead.org>]

On Fri, Sep 18, 2026 at 09:29:15PM +0800, Zhan Xusheng wrote:
> psi_account_irqtime() has two callers which share rq->psi_irq_time, and
> they disagree about the context: __schedule() passes the outgoing rq->curr,
> sched_tick() passes rq->donor.  Under proxy execution the donor is blocked
> on a mutex while rq->curr burns the CPU.
> 
> The tick charges PSI_IRQ_FULL to the donor's cgroup and advances the
> timestamp, so the call from __schedule() then finds delta <= 0 and charges
> nothing.  The delta is not counted twice, it lands on the wrong cgroup.
> 
> Pass rq->curr, which is what the call read before commit af0c8b2bf67b
> ("sched: Split scheduler and execution contexts") renamed curr to donor
> across sched_tick().  Without CONFIG_SCHED_PROXY_EXEC the two rq members
> are a union, so this only changes anything where that option is set, and
> it depends on EXPERT.
> 
> Fixes: af0c8b2bf67b ("sched: Split scheduler and execution contexts")
> Signed-off-by: Zhan Xusheng <zhanxusheng@xiaomi.com>
> ---
> Built and booted on x86_64 with CONFIG_SCHED_PROXY_EXEC=y, PSI and
> IRQ_TIME_ACCOUNTING enabled, under x86_debug.config and panic_on_warn.
> I did not construct a case where donor and curr differ.
>  kernel/sched/core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 7885ff76e69f..2b48ae0ab372 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -5791,7 +5791,7 @@ void sched_tick(void)
>  	curr = rq->curr;
>  	donor = rq->donor;
>  
> -	psi_account_irqtime(rq, donor, NULL);
> +	psi_account_irqtime(rq, curr, NULL);
>  
>  	update_rq_clock(rq);
>  	hw_pressure = arch_scale_hw_pressure(cpu_of(rq));

Does not in fact apply. There is no curr in sched_tick anymore.