linux-kernel - [PATCH -next v2] sched/deadline: Add dl_task_is_earliest

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Date:   Fri, 26 Aug 2022 16:34:53 +0800
From:   Shang XiaoJing <shangxiaojing@...wei.com>
To:     <mingo@...hat.com>, <peterz@...radead.org>,
        <juri.lelli@...hat.com>, <vincent.guittot@...aro.org>,
        <dietmar.eggemann@....com>, <rostedt@...dmis.org>,
        <bsegall@...gle.com>, <mgorman@...e.de>, <bristot@...hat.com>,
        <vschneid@...hat.com>, <linux-kernel@...r.kernel.org>
CC:     <shangxiaojing@...wei.com>
Subject: [PATCH -next v2] sched/deadline: Add dl_task_is_earliest_deadline helper

Wrap repeated code in helper function dl_task_is_earliest_deadline, which
return true if there is no deadline task on the rq at all, or task's
deadline earlier than the whole rq.

Signed-off-by: Shang XiaoJing <shangxiaojing@...wei.com>
---
changes in v2:
- pick a more descriptive function name rather than compare_task_rq.
---
 kernel/sched/deadline.c | 24 ++++++++++++------------
 1 file changed, 12 insertions(+), 12 deletions(-)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index d116d2b9d2f9..34271aff4712 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1810,6 +1810,14 @@ static void yield_task_dl(struct rq *rq)
 
 #ifdef CONFIG_SMP
 
+static inline bool dl_task_is_earliest_deadline(struct task_struct *p,
+						 struct rq *rq)
+{
+	return (!rq->dl.dl_nr_running ||
+		dl_time_before(p->dl.deadline,
+			       rq->dl.earliest_dl.curr));
+}
+
 static int find_later_rq(struct task_struct *task);
 
 static int
@@ -1852,9 +1860,7 @@ select_task_rq_dl(struct task_struct *p, int cpu, int flags)
 		int target = find_later_rq(p);
 
 		if (target != -1 &&
-				(dl_time_before(p->dl.deadline,
-					cpu_rq(target)->dl.earliest_dl.curr) ||
-				(cpu_rq(target)->dl.dl_nr_running == 0)))
+		    dl_task_is_earliest_deadline(p, cpu_rq(target)))
 			cpu = target;
 	}
 	rcu_read_unlock();
@@ -2221,9 +2227,7 @@ static struct rq *find_lock_later_rq(struct task_struct *task, struct rq *rq)
 
 		later_rq = cpu_rq(cpu);
 
-		if (later_rq->dl.dl_nr_running &&
-		    !dl_time_before(task->dl.deadline,
-					later_rq->dl.earliest_dl.curr)) {
+		if (!dl_task_is_earliest_deadline(task, later_rq)) {
 			/*
 			 * Target rq has tasks of equal or earlier deadline,
 			 * retrying does not release any lock and is unlikely
@@ -2251,9 +2255,7 @@ static struct rq *find_lock_later_rq(struct task_struct *task, struct rq *rq)
 		 * its earliest one has a later deadline than our
 		 * task, the rq is a good one.
 		 */
-		if (!later_rq->dl.dl_nr_running ||
-		    dl_time_before(task->dl.deadline,
-				   later_rq->dl.earliest_dl.curr))
+		if (dl_task_is_earliest_deadline(task, later_rq))
 			break;
 
 		/* Otherwise we try again. */
@@ -2424,9 +2426,7 @@ static void pull_dl_task(struct rq *this_rq)
 		 *  - it will preempt the last one we pulled (if any).
 		 */
 		if (p && dl_time_before(p->dl.deadline, dmin) &&
-		    (!this_rq->dl.dl_nr_running ||
-		     dl_time_before(p->dl.deadline,
-				    this_rq->dl.earliest_dl.curr))) {
+		    dl_task_is_earliest_deadline(p, this_rq)) {
 			WARN_ON(p == src_rq->curr);
 			WARN_ON(!task_on_rq_queued(p));
 
-- 
2.17.1