linux-kernel - [PATCH v4 3/5] sched/deadline: Change return value of cpudl

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Date:   Fri, 12 May 2017 14:48:47 +0900
From:   Byungchul Park <byungchul.park@....com>
To:     <peterz@...radead.org>, <mingo@...nel.org>
CC:     <linux-kernel@...r.kernel.org>, <juri.lelli@...il.com>,
        <rostedt@...dmis.org>, <bristot@...hat.com>, <kernel-team@....com>
Subject: [PATCH v4 3/5] sched/deadline: Change return value of cpudl_find()

Currently cpudl_find() returns the best cpu that means it has the
maximum dl, however, the value is already kept in later_mask and the
return value is not referred directly any more.

Now, it's enough to return whether CPUs were found or not, like rt.

Signed-off-by: Byungchul Park <byungchul.park@....com>
---
 kernel/sched/cpudeadline.c | 13 +++++--------
 kernel/sched/deadline.c    |  6 +++---
 2 files changed, 8 insertions(+), 11 deletions(-)

diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c
index 6b67016..28d057f 100644
--- a/kernel/sched/cpudeadline.c
+++ b/kernel/sched/cpudeadline.c
@@ -119,18 +119,16 @@ static inline int cpudl_maximum(struct cpudl *cp)
  * @p: the task
  * @later_mask: a mask to fill in with the selected CPUs (or NULL)
  *
- * Returns: int - best CPU (heap maximum if suitable)
+ * Returns: (int)bool - CPUs were found
  */
 int cpudl_find(struct cpudl *cp, struct task_struct *p,
 	       struct cpumask *later_mask)
 {
-	int best_cpu = -1;
 	const struct sched_dl_entity *dl_se = &p->dl;
 
 	if (later_mask &&
 	    cpumask_and(later_mask, cp->free_cpus, &p->cpus_allowed)) {
-		best_cpu = cpumask_any(later_mask);
-		goto out;
+		return 1;
 	} else {
 		u64 cpudl_dl;
 		int cpudl_cpu;
@@ -157,14 +155,13 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p,
 		if (cpudl_valid != IDX_INVALID &&
 		    cpumask_test_cpu(cpudl_cpu, &p->cpus_allowed) &&
 		    dl_time_before(dl_se->deadline, cpudl_dl)) {
-			best_cpu = cpudl_cpu;
 			if (later_mask)
-				cpumask_set_cpu(best_cpu, later_mask);
+				cpumask_set_cpu(cpudl_cpu, later_mask);
+			return 1;
 		}
 	}
 
-out:
-	return best_cpu;
+	return 0;
 }
 
 /*
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 9d997d9..0223694 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1107,7 +1107,7 @@ static void check_preempt_equal_dl(struct rq *rq, struct task_struct *p)
 	 * let's hope p can move out.
 	 */
 	if (rq->curr->nr_cpus_allowed == 1 ||
-	    cpudl_find(&rq->rd->cpudl, rq->curr, NULL) == -1)
+	    !cpudl_find(&rq->rd->cpudl, rq->curr, NULL))
 		return;
 
 	/*
@@ -1115,7 +1115,7 @@ static void check_preempt_equal_dl(struct rq *rq, struct task_struct *p)
 	 * see if it is pushed or pulled somewhere else.
 	 */
 	if (p->nr_cpus_allowed != 1 &&
-	    cpudl_find(&rq->rd->cpudl, p, NULL) != -1)
+	    cpudl_find(&rq->rd->cpudl, p, NULL))
 		return;
 
 	resched_curr(rq);
@@ -1337,7 +1337,7 @@ static int find_later_rq(struct task_struct *task)
 	 * We have to consider system topology and task affinity
 	 * first, then we can look for a suitable cpu.
 	 */
-	if (cpudl_find(&task_rq(task)->rd->cpudl, task, later_mask) == -1)
+	if (!cpudl_find(&task_rq(task)->rd->cpudl, task, later_mask))
 		return -1;
 
 	/*
-- 
1.9.1