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Message-ID: <aLhUB86NwnaQ8bMf@jlelli-thinkpadt14gen4.remote.csb>
Date: Wed, 3 Sep 2025 16:43:19 +0200
From: Juri Lelli <juri.lelli@...hat.com>
To: Andrea Righi <arighi@...dia.com>
Cc: Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>,
Vincent Guittot <vincent.guittot@...aro.org>,
Dietmar Eggemann <dietmar.eggemann@....com>,
Steven Rostedt <rostedt@...dmis.org>,
Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
Valentin Schneider <vschneid@...hat.com>,
Joel Fernandes <joelagnelf@...dia.com>, Tejun Heo <tj@...nel.org>,
David Vernet <void@...ifault.com>,
Changwoo Min <changwoo@...lia.com>, Shuah Khan <shuah@...nel.org>,
sched-ext@...ts.linux.dev, bpf@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 03/16] sched/debug: Stop and start server based on if it
was active
Hi,
On 03/09/25 11:33, Andrea Righi wrote:
> From: Joel Fernandes <joelagnelf@...dia.com>
>
> Currently the DL server interface for applying parameters checks
> CFS-internals to identify if the server is active. This is error-prone
> and makes it difficult when adding new servers in the future.
>
> Fix it, by using dl_server_active() which is also used by the DL server
> code to determine if the DL server was started.
>
> Acked-by: Tejun Heo <tj@...nel.org>
> Reviewed-by: Andrea Righi <arighi@...dia.com>
> Signed-off-by: Joel Fernandes <joelagnelf@...dia.com>
> ---
> kernel/sched/debug.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
> index dbe2aee8628ce..e71f6618c1a6a 100644
> --- a/kernel/sched/debug.c
> +++ b/kernel/sched/debug.c
> @@ -354,6 +354,8 @@ static ssize_t sched_fair_server_write(struct file *filp, const char __user *ubu
> return err;
>
> scoped_guard (rq_lock_irqsave, rq) {
> + bool is_active;
> +
> runtime = rq->fair_server.dl_runtime;
> period = rq->fair_server.dl_period;
>
> @@ -376,7 +378,8 @@ static ssize_t sched_fair_server_write(struct file *filp, const char __user *ubu
> return -EINVAL;
> }
>
> - if (rq->cfs.h_nr_queued) {
> + is_active = dl_server_active(&rq->fair_server);
> + if (is_active) {
> update_rq_clock(rq);
> dl_server_stop(&rq->fair_server);
> }
I believe this chunk will unfortunately conflict with bb4700adc3ab
("sched/deadline: Always stop dl-server before changing parameters"),
but it should be an easy fix. :)
Thanks,
Juri
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