linux-kernel - [PATCH 1/6] sched/deadline: Consolidate the SCHED_DL task_can

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Date:   Tue, 12 Jan 2021 16:53:40 +0100
From:   Daniel Bristot de Oliveira <bristot@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     Marco Perronet <perronet@...-sws.org>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        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>,
        Li Zefan <lizefan@...wei.com>, Tejun Heo <tj@...nel.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Valentin Schneider <valentin.schneider@....com>,
        cgroups@...r.kernel.org
Subject: [PATCH 1/6] sched/deadline: Consolidate the SCHED_DL task_can_attach() check on its own function

It is easier to track the restrictions imposed on SCHED_DEADLINE
tasks if we keep them all together in a single function.

No function changes.

Signed-off-by: Daniel Bristot de Oliveira <bristot@...hat.com>
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: Steven Rostedt <rostedt@...dmis.org>
Cc: Ben Segall <bsegall@...gle.com>
Cc: Mel Gorman <mgorman@...e.de>
Cc: Daniel Bristot de Oliveira <bristot@...hat.com>
Cc: Li Zefan <lizefan@...wei.com>
Cc: Tejun Heo <tj@...nel.org>
Cc: Johannes Weiner <hannes@...xchg.org>
Cc: Valentin Schneider <valentin.schneider@....com>
Cc: linux-kernel@...r.kernel.org
Cc: cgroups@...r.kernel.org
---
 kernel/sched/core.c     | 3 +--
 kernel/sched/deadline.c | 7 +++++++
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 7af80c3fce12..f4aede34449c 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7142,8 +7142,7 @@ int task_can_attach(struct task_struct *p,
 		goto out;
 	}
 
-	if (dl_task(p) && !cpumask_intersects(task_rq(p)->rd->span,
-					      cs_cpus_allowed))
+	if (dl_task(p))
 		ret = dl_task_can_attach(p, cs_cpus_allowed);
 
 out:
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 75686c6d4436..c97d2c707b98 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -2870,6 +2870,13 @@ int dl_task_can_attach(struct task_struct *p, const struct cpumask *cs_cpus_allo
 	bool overflow;
 	int ret;
 
+	/*
+	 * The task is not moving to another root domain, so it is
+	 * already accounted.
+	 */
+	if (cpumask_intersects(task_rq(p)->rd->span, cs_cpus_allowed))
+		return 0;
+
 	dest_cpu = cpumask_any_and(cpu_active_mask, cs_cpus_allowed);
 
 	rcu_read_lock_sched();
-- 
2.29.2