linux-kernel - Re: [PATCH v16 1/7] sched: Add CONFIG_SCHED_PROXY

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Message-ID: <Z_zMWkvtACZxahu-@jlelli-thinkpadt14gen4.remote.csb>
Date: Mon, 14 Apr 2025 10:50:34 +0200
From: Juri Lelli <juri.lelli@...hat.com>
To: John Stultz <jstultz@...gle.com>
Cc: LKML <linux-kernel@...r.kernel.org>,
	Joel Fernandes <joelagnelf@...dia.com>,
	Qais Yousef <qyousef@...alina.io>, Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Valentin Schneider <vschneid@...hat.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ben Segall <bsegall@...gle.com>,
	Zimuzo Ezeozue <zezeozue@...gle.com>, Mel Gorman <mgorman@...e.de>,
	Will Deacon <will@...nel.org>, Waiman Long <longman@...hat.com>,
	Boqun Feng <boqun.feng@...il.com>,
	"Paul E. McKenney" <paulmck@...nel.org>,
	Metin Kaya <Metin.Kaya@....com>,
	Xuewen Yan <xuewen.yan94@...il.com>,
	K Prateek Nayak <kprateek.nayak@....com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Suleiman Souhlal <suleiman@...gle.com>, kernel-team@...roid.com
Subject: Re: [PATCH v16 1/7] sched: Add CONFIG_SCHED_PROXY_EXEC & boot
 argument to enable/disable

Hi John,

On 11/04/25 23:02, John Stultz wrote:
> Add a CONFIG_SCHED_PROXY_EXEC option, along with a boot argument
> sched_proxy_exec= that can be used to disable the feature at boot
> time if CONFIG_SCHED_PROXY_EXEC was enabled.
> 
> Cc: Joel Fernandes <joelagnelf@...dia.com>
> Cc: Qais Yousef <qyousef@...alina.io>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Juri Lelli <juri.lelli@...hat.com>
> Cc: Vincent Guittot <vincent.guittot@...aro.org>
> Cc: Dietmar Eggemann <dietmar.eggemann@....com>
> Cc: Valentin Schneider <vschneid@...hat.com>
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Cc: Ben Segall <bsegall@...gle.com>
> Cc: Zimuzo Ezeozue <zezeozue@...gle.com>
> Cc: Mel Gorman <mgorman@...e.de>
> Cc: Will Deacon <will@...nel.org>
> Cc: Waiman Long <longman@...hat.com>
> Cc: Boqun Feng <boqun.feng@...il.com>
> Cc: "Paul E. McKenney" <paulmck@...nel.org>
> Cc: Metin Kaya <Metin.Kaya@....com>
> Cc: Xuewen Yan <xuewen.yan94@...il.com>
> Cc: K Prateek Nayak <kprateek.nayak@....com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Daniel Lezcano <daniel.lezcano@...aro.org>
> Cc: Suleiman Souhlal <suleiman@...gle.com>
> Cc: kernel-team@...roid.com
> Tested-by: K Prateek Nayak <kprateek.nayak@....com>
> Signed-off-by: John Stultz <jstultz@...gle.com>
> ---

...

> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index 47972f34ea701..154f0aa0c6322 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -1149,10 +1149,15 @@ struct rq {
>  	 */
>  	unsigned int		nr_uninterruptible;
>  
> +#ifdef CONFIG_SCHED_PROXY_EXEC
> +	struct task_struct __rcu	*donor;  /* Scheduling context */
> +	struct task_struct __rcu	*curr;   /* Execution context */
> +#else
>  	union {
>  		struct task_struct __rcu *donor; /* Scheduler context */
>  		struct task_struct __rcu *curr;  /* Execution context */
>  	};
> +#endif
>  	struct sched_dl_entity	*dl_server;
>  	struct task_struct	*idle;
>  	struct task_struct	*stop;
> @@ -1347,10 +1352,17 @@ DECLARE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
>  #define cpu_curr(cpu)		(cpu_rq(cpu)->curr)
>  #define raw_rq()		raw_cpu_ptr(&runqueues)
>  
> +#ifdef CONFIG_SCHED_PROXY_EXEC
> +static inline void rq_set_donor(struct rq *rq, struct task_struct *t)
> +{
> +	rcu_assign_pointer(rq->donor, t);
> +}
> +#else
>  static inline void rq_set_donor(struct rq *rq, struct task_struct *t)
>  {
>  	/* Do nothing */
>  }
> +#endif

Does this chunk belong here?

Thanks,
Juri