linux-kernel - Re: [PATCH 1/5] sched/deadline: Initialize dl

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Message-ID: <495e2880-db0c-45d5-9cbc-e9299ba8a6b8@redhat.com>
Date: Mon, 30 Jun 2025 13:04:21 -0400
From: Waiman Long <llong@...hat.com>
To: Juri Lelli <juri.lelli@...hat.com>, Waiman Long <llong@...hat.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>,
 linux-kernel@...r.kernel.org,
 Marcel Ziswiler <marcel.ziswiler@...ethink.co.uk>,
 Luca Abeni <luca.abeni@...tannapisa.it>
Subject: Re: [PATCH 1/5] sched/deadline: Initialize dl_servers after SMP


On 6/30/25 6:21 AM, Juri Lelli wrote:
> On 29/06/25 18:48, Waiman Long wrote:
>> On 6/27/25 7:51 AM, Juri Lelli wrote:
> ...
>
>>> @@ -1652,6 +1664,8 @@ int dl_server_apply_params(struct sched_dl_entity *dl_se, u64 runtime, u64 perio
>>>    	int retval = 0;
>>>    	int cpus;
>>> +	guard(rcu)();
>>> +
>> Your patch doesn't explain why a RCU guard is needed here?
>> sched_init_dl_servers() is the changed caller, but it is called with
>> rq_lock_irq held which should implies a RCU read critical section as IRQ is
>> disabled.
> Yeah, looks like it's not required. Will remove. Thanks for spotting it!

Other than this minor nit, the patch series look good to me with my 
limited understanding about the DL scheduler.

Acked-by: Waiman Long <longman@...hat.com>