linux-kernel - Re: [RFC][PATCH 12/13] sched/deadline: Introduce deadline servers

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Message-ID: <b85f1f95-40e5-852b-f897-1379414354c9@arm.com>
Date:   Fri, 9 Aug 2019 11:17:18 +0200
From:   Dietmar Eggemann <dietmar.eggemann@....com>
To:     Peter Zijlstra <peterz@...radead.org>, mingo@...nel.org,
        juri.lelli@...hat.com
Cc:     linux-kernel@...r.kernel.org, luca.abeni@...tannapisa.it,
        bristot@...hat.com, balsini@...roid.com, dvyukov@...gle.com,
        tglx@...utronix.de, vpillai@...italocean.com, rostedt@...dmis.org
Subject: Re: [RFC][PATCH 12/13] sched/deadline: Introduce deadline servers

On 7/26/19 4:54 PM, Peter Zijlstra wrote:

[...]

> +void dl_server_init(struct sched_dl_entity *dl_se, struct rq *rq,
> +		    dl_server_has_tasks_f has_tasks,
> +		    dl_server_pick_f pick)
> +{
> +	dl_se->dl_server = 1;
> +	dl_se->rq = rq;
> +	dl_se->server_has_tasks = has_tasks;
> +	dl_se->server_pick = pick;
> +
> +	setup_new_dl_entity(dl_se);

IMHO, this needs rq locking because of the rq_clock(rq) in
setup_new_dl_entity().

[    0.000000] WARNING: CPU: 0 PID: 0 at kernel/sched/sched.h:1119
dl_server_init+0x118/0x178
...
[    0.000000] CPU: 0 PID: 0 Comm: swapper Tainted: G        W
5.3.0-rc3-00013-ga33cf033cc99-dirty #10
[    0.000000] Hardware name: ARM Juno development board (r0) (DT)
...
[    0.000000] Call trace:
[    0.000000]  dl_server_init+0x118/0x178
[    0.000000]  fair_server_init+0x5c/0x68
[    0.000000]  sched_init+0x2c8/0x474
[    0.000000]  start_kernel+0x290/0x514

[...]