linux-kernel - [RFC PATCH v3 04/16] sched/{rt,deadline}: Fix set_next_task vs pick_next

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Date:   Wed, 29 May 2019 20:36:40 +0000
From:   Vineeth Remanan Pillai <vpillai@...italocean.com>
To:     Nishanth Aravamudan <naravamudan@...italocean.com>,
        Julien Desfossez <jdesfossez@...italocean.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>, mingo@...nel.org,
        tglx@...utronix.de, pjt@...gle.com, torvalds@...ux-foundation.org
Cc:     linux-kernel@...r.kernel.org, subhra.mazumdar@...cle.com,
        fweisbec@...il.com, keescook@...omium.org, kerrnel@...gle.com,
        Phil Auld <pauld@...hat.com>, Aaron Lu <aaron.lwe@...il.com>,
        Aubrey Li <aubrey.intel@...il.com>,
        Valentin Schneider <valentin.schneider@....com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: [RFC PATCH v3 04/16] sched/{rt,deadline}: Fix set_next_task vs pick_next_task

From: Peter Zijlstra <peterz@...radead.org>

Because pick_next_task() implies set_curr_task() and some of the
details haven't matter too much, some of what _should_ be in
set_curr_task() ended up in pick_next_task, correct this.

This prepares the way for a pick_next_task() variant that does not
affect the current state; allowing remote picking.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 kernel/sched/deadline.c | 23 ++++++++++++-----------
 kernel/sched/rt.c       | 27 ++++++++++++++-------------
 2 files changed, 26 insertions(+), 24 deletions(-)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index e683d4c19ab8..0783dfa65150 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1694,12 +1694,21 @@ static void start_hrtick_dl(struct rq *rq, struct task_struct *p)
 }
 #endif
 
-static inline void set_next_task(struct rq *rq, struct task_struct *p)
+static void set_next_task_dl(struct rq *rq, struct task_struct *p)
 {
 	p->se.exec_start = rq_clock_task(rq);
 
 	/* You can't push away the running task */
 	dequeue_pushable_dl_task(rq, p);
+
+	if (hrtick_enabled(rq))
+		start_hrtick_dl(rq, p);
+
+	if (rq->curr->sched_class != &dl_sched_class)
+		update_dl_rq_load_avg(rq_clock_pelt(rq), rq, 0);
+
+	if (rq->curr != p)
+		deadline_queue_push_tasks(rq);
 }
 
 static struct sched_dl_entity *pick_next_dl_entity(struct rq *rq,
@@ -1758,15 +1767,7 @@ pick_next_task_dl(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
 
 	p = dl_task_of(dl_se);
 
-	set_next_task(rq, p);
-
-	if (hrtick_enabled(rq))
-		start_hrtick_dl(rq, p);
-
-	deadline_queue_push_tasks(rq);
-
-	if (rq->curr->sched_class != &dl_sched_class)
-		update_dl_rq_load_avg(rq_clock_pelt(rq), rq, 0);
+	set_next_task_dl(rq, p);
 
 	return p;
 }
@@ -1813,7 +1814,7 @@ static void task_fork_dl(struct task_struct *p)
 
 static void set_curr_task_dl(struct rq *rq)
 {
-	set_next_task(rq, rq->curr);
+	set_next_task_dl(rq, rq->curr);
 }
 
 #ifdef CONFIG_SMP
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 3d9db8c75d53..353ad960691b 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -1498,12 +1498,23 @@ static void check_preempt_curr_rt(struct rq *rq, struct task_struct *p, int flag
 #endif
 }
 
-static inline void set_next_task(struct rq *rq, struct task_struct *p)
+static inline void set_next_task_rt(struct rq *rq, struct task_struct *p)
 {
 	p->se.exec_start = rq_clock_task(rq);
 
 	/* The running task is never eligible for pushing */
 	dequeue_pushable_task(rq, p);
+
+	/*
+	 * If prev task was rt, put_prev_task() has already updated the
+	 * utilization. We only care of the case where we start to schedule a
+	 * rt task
+	 */
+	if (rq->curr->sched_class != &rt_sched_class)
+		update_rt_rq_load_avg(rq_clock_pelt(rq), rq, 0);
+
+	if (rq->curr != p)
+		rt_queue_push_tasks(rq);
 }
 
 static struct sched_rt_entity *pick_next_rt_entity(struct rq *rq,
@@ -1577,17 +1588,7 @@ pick_next_task_rt(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
 
 	p = _pick_next_task_rt(rq);
 
-	set_next_task(rq, p);
-
-	rt_queue_push_tasks(rq);
-
-	/*
-	 * If prev task was rt, put_prev_task() has already updated the
-	 * utilization. We only care of the case where we start to schedule a
-	 * rt task
-	 */
-	if (rq->curr->sched_class != &rt_sched_class)
-		update_rt_rq_load_avg(rq_clock_pelt(rq), rq, 0);
+	set_next_task_rt(rq, p);
 
 	return p;
 }
@@ -2356,7 +2357,7 @@ static void task_tick_rt(struct rq *rq, struct task_struct *p, int queued)
 
 static void set_curr_task_rt(struct rq *rq)
 {
-	set_next_task(rq, rq->curr);
+	set_next_task_rt(rq, rq->curr);
 }
 
 static unsigned int get_rr_interval_rt(struct rq *rq, struct task_struct *task)
-- 
2.17.1