linux-kernel - [tip: sched/core] sched/core: Make pick_next_task

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Date:   Mon, 11 Nov 2019 09:32:35 -0000
From:   "tip-bot2 for Peter Zijlstra" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>, bsegall@...gle.com,
        dietmar.eggemann@....com, juri.lelli@...hat.com,
        ktkhai@...tuozzo.com, mgorman@...e.de, qais.yousef@....com,
        qperret@...gle.com, rostedt@...dmis.org,
        valentin.schneider@....com, vincent.guittot@...aro.org,
        Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>,
        linux-kernel@...r.kernel.org
Subject: [tip: sched/core] sched/core: Make pick_next_task_idle() more consistent

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     f488e1057bb97b881ed317557dc5e62ff8747393
Gitweb:        https://git.kernel.org/tip/f488e1057bb97b881ed317557dc5e62ff8747393
Author:        Peter Zijlstra <peterz@...radead.org>
AuthorDate:    Fri, 08 Nov 2019 14:15:56 +01:00
Committer:     Ingo Molnar <mingo@...nel.org>
CommitterDate: Mon, 11 Nov 2019 08:35:19 +01:00

sched/core: Make pick_next_task_idle() more consistent

Only pick_next_task_fair() needs the @prev and @rf argument; these are
required to implement the cpu-cgroup optimization. None of the other
pick_next_task() methods need this. Make pick_next_task_idle() more
consistent.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: bsegall@...gle.com
Cc: dietmar.eggemann@....com
Cc: juri.lelli@...hat.com
Cc: ktkhai@...tuozzo.com
Cc: mgorman@...e.de
Cc: qais.yousef@....com
Cc: qperret@...gle.com
Cc: rostedt@...dmis.org
Cc: valentin.schneider@....com
Cc: vincent.guittot@...aro.org
Link: https://lkml.kernel.org/r/20191108131909.545730862@infradead.org
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 kernel/sched/core.c | 6 ++++--
 kernel/sched/idle.c | 3 +--
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 0f2eb36..59c4f29 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3922,8 +3922,10 @@ pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
 			goto restart;
 
 		/* Assumes fair_sched_class->next == idle_sched_class */
-		if (unlikely(!p))
-			p = idle_sched_class.pick_next_task(rq, prev, rf);
+		if (unlikely(!p)) {
+			put_prev_task(rq, prev);
+			p = idle_sched_class.pick_next_task(rq, NULL, NULL);
+		}
 
 		return p;
 	}
diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
index f65ef1e..179d1d4 100644
--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -396,8 +396,7 @@ pick_next_task_idle(struct rq *rq, struct task_struct *prev, struct rq_flags *rf
 {
 	struct task_struct *next = rq->idle;
 
-	if (prev)
-		put_prev_task(rq, prev);
+	WARN_ON_ONCE(prev || rf);
 
 	set_next_task_idle(rq, next);