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Date: Tue, 4 Jun 2024 14:12:04 +0100
From: Qais Yousef <qyousef@layalina.io>
To: John Stultz <jstultz@google.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
	Connor O'Brien <connoro@google.com>,
	Joel Fernandes <joelaf@google.com>, Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Juri Lelli <juri.lelli@redhat.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Valentin Schneider <vschneid@redhat.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Ben Segall <bsegall@google.com>,
	Zimuzo Ezeozue <zezeozue@google.com>,
	Youssef Esmat <youssefesmat@google.com>,
	Mel Gorman <mgorman@suse.de>,
	Daniel Bristot de Oliveira <bristot@redhat.com>,
	Will Deacon <will@kernel.org>, Waiman Long <longman@redhat.com>,
	Boqun Feng <boqun.feng@gmail.com>,
	"Paul E. McKenney" <paulmck@kernel.org>,
	Metin Kaya <Metin.Kaya@arm.com>,
	Xuewen Yan <xuewen.yan94@gmail.com>,
	K Prateek Nayak <kprateek.nayak@amd.com>,
	Thomas Gleixner <tglx@linutronix.de>, kernel-team@android.com
Subject: Re: [PATCH v10 4/7] sched: Add move_queued_task_locked helper
Message-ID: <20240604131204.n4njtgo4tpo352ht@airbuntu>
References: <20240507045450.895430-1-jstultz@google.com>
 <20240507045450.895430-5-jstultz@google.com>
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In-Reply-To: <20240507045450.895430-5-jstultz@google.com>

On 05/06/24 21:54, John Stultz wrote:
> From: Connor O'Brien <connoro@google.com>
> 
> Switch logic that deactivates, sets the task cpu,
> and reactivates a task on a different rq to use a
> helper that will be later extended to push entire
> blocked task chains.
> 
> This patch was broken out from a larger chain migration
> patch originally by Connor O'Brien.
> 
> Cc: Joel Fernandes <joelaf@google.com>
> Cc: Qais Yousef <qyousef@layalina.io>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Juri Lelli <juri.lelli@redhat.com>
> Cc: Vincent Guittot <vincent.guittot@linaro.org>
> Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
> Cc: Valentin Schneider <vschneid@redhat.com>
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Cc: Ben Segall <bsegall@google.com>
> Cc: Zimuzo Ezeozue <zezeozue@google.com>
> Cc: Youssef Esmat <youssefesmat@google.com>
> Cc: Mel Gorman <mgorman@suse.de>
> Cc: Daniel Bristot de Oliveira <bristot@redhat.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: Waiman Long <longman@redhat.com>
> Cc: Boqun Feng <boqun.feng@gmail.com>
> Cc: "Paul E. McKenney" <paulmck@kernel.org>
> Cc: Metin Kaya <Metin.Kaya@arm.com>
> Cc: Xuewen Yan <xuewen.yan94@gmail.com>
> Cc: K Prateek Nayak <kprateek.nayak@amd.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: kernel-team@android.com
> Tested-by: K Prateek Nayak <kprateek.nayak@amd.com>
> Tested-by: Metin Kaya <metin.kaya@arm.com>
> Reviewed-by: Metin Kaya <metin.kaya@arm.com>
> Reviewed-by: Valentin Schneider <vschneid@redhat.com>
> Signed-off-by: Connor O'Brien <connoro@google.com>
> [jstultz: split out from larger chain migration patch]
> Signed-off-by: John Stultz <jstultz@google.com>
> ---
> v8:
> * Renamed from push_task_chain to do_push_task so it makes
>   more sense without proxy-execution
> v10:
> * Changed name to move_queued_task_locked as suggested by Valentin
> ---
>  kernel/sched/core.c     |  4 +---
>  kernel/sched/deadline.c |  8 ++------
>  kernel/sched/rt.c       |  8 ++------
>  kernel/sched/sched.h    | 11 +++++++++++
>  4 files changed, 16 insertions(+), 15 deletions(-)
> 
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 7019a40457a6..48f0d4b381d5 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -2712,9 +2712,7 @@ int push_cpu_stop(void *arg)
>  
>  	// XXX validate p is still the highest prio task
>  	if (task_rq(p) == rq) {
> -		deactivate_task(rq, p, 0);
> -		set_task_cpu(p, lowest_rq->cpu);
> -		activate_task(lowest_rq, p, 0);
> +		move_queued_task_locked(rq, lowest_rq, p);
>  		resched_curr(lowest_rq);
>  	}
>  
> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
> index a04a436af8cc..eaedc69c5e30 100644
> --- a/kernel/sched/deadline.c
> +++ b/kernel/sched/deadline.c
> @@ -2443,9 +2443,7 @@ static int push_dl_task(struct rq *rq)
>  		goto retry;
>  	}
>  
> -	deactivate_task(rq, next_task, 0);
> -	set_task_cpu(next_task, later_rq->cpu);
> -	activate_task(later_rq, next_task, 0);
> +	move_queued_task_locked(rq, later_rq, next_task);
>  	ret = 1;
>  
>  	resched_curr(later_rq);
> @@ -2531,9 +2529,7 @@ static void pull_dl_task(struct rq *this_rq)
>  			if (is_migration_disabled(p)) {
>  				push_task = get_push_task(src_rq);
>  			} else {
> -				deactivate_task(src_rq, p, 0);
> -				set_task_cpu(p, this_cpu);
> -				activate_task(this_rq, p, 0);
> +				move_queued_task_locked(src_rq, this_rq, p);
>  				dmin = p->dl.deadline;
>  				resched = true;
>  			}
> diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
> index 3261b067b67e..975cb49a64dc 100644
> --- a/kernel/sched/rt.c
> +++ b/kernel/sched/rt.c
> @@ -2106,9 +2106,7 @@ static int push_rt_task(struct rq *rq, bool pull)
>  		goto retry;
>  	}
>  
> -	deactivate_task(rq, next_task, 0);
> -	set_task_cpu(next_task, lowest_rq->cpu);
> -	activate_task(lowest_rq, next_task, 0);
> +	move_queued_task_locked(rq, lowest_rq, next_task);
>  	resched_curr(lowest_rq);
>  	ret = 1;
>  
> @@ -2379,9 +2377,7 @@ static void pull_rt_task(struct rq *this_rq)
>  			if (is_migration_disabled(p)) {
>  				push_task = get_push_task(src_rq);
>  			} else {
> -				deactivate_task(src_rq, p, 0);
> -				set_task_cpu(p, this_cpu);
> -				activate_task(this_rq, p, 0);
> +				move_queued_task_locked(src_rq, this_rq, p);
>  				resched = true;
>  			}
>  			/*
> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index ae50f212775e..2d41ebe200c7 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -3480,5 +3480,16 @@ static inline void init_sched_mm_cid(struct task_struct *t) { }
>  
>  extern u64 avg_vruntime(struct cfs_rq *cfs_rq);
>  extern int entity_eligible(struct cfs_rq *cfs_rq, struct sched_entity *se);
> +#ifdef CONFIG_SMP
> +static inline
> +void move_queued_task_locked(struct rq *rq, struct rq *dst_rq, struct task_struct *task)
> +{
> +	lockdep_assert_rq_held(rq);
> +	lockdep_assert_rq_held(dst_rq);
> +	deactivate_task(rq, task, 0);
> +	set_task_cpu(task, dst_rq->cpu);
> +	activate_task(dst_rq, task, 0);
> +}
> +#endif

I see this pattern in __migrate_swap_task() and try_steal_cookie(), should they
be converted to?

Beside this

Reviewed-by: Qais Yousef <qyousef@layalina.io>

>  
>  #endif /* _KERNEL_SCHED_SCHED_H */
> -- 
> 2.45.0.rc1.225.g2a3ae87e7f-goog
>