linux-kernel - [PATCH v3 14/18] locking/lockdep: Change the return type of __cq

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Message-Id: <20190321075725.14054-15-duyuyang@gmail.com>
Date:   Thu, 21 Mar 2019 15:57:21 +0800
From:   Yuyang Du <duyuyang@...il.com>
To:     peterz@...radead.org, will.deacon@....com, mingo@...nel.org
Cc:     bvanassche@....org, ming.lei@...hat.com,
        linux-kernel@...r.kernel.org, joe@...ches.com,
        Yuyang Du <duyuyang@...il.com>
Subject: [PATCH v3 14/18] locking/lockdep: Change the return type of __cq_dequeue()

With the change, we can slightly adjust the code to iterate the queue in BFS
search, which simplifies the code. No functional change.

Signed-off-by: Yuyang Du <duyuyang@...il.com>
---
 kernel/locking/lockdep.c | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 8167d69..ad16793 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -1317,14 +1317,21 @@ static inline int __cq_enqueue(struct circular_queue *cq, struct lock_list *elem
 	return 0;
 }
 
-static inline int __cq_dequeue(struct circular_queue *cq, struct lock_list **elem)
+/*
+ * Dequeue an element from the circular_queue, return the lock if the queue
+ * is not empty, or NULL if otherwise
+ */
+static inline struct lock_list * __cq_dequeue(struct circular_queue *cq)
 {
+	struct lock_list * lock;
+
 	if (__cq_empty(cq))
-		return -1;
+		return NULL;
 
-	*elem = cq->element[cq->front];
+	lock = cq->element[cq->front];
 	cq->front = (cq->front + 1) & CQ_MASK;
-	return 0;
+
+	return lock;
 }
 
 static inline unsigned int  __cq_get_elem_count(struct circular_queue *cq)
@@ -1376,6 +1383,7 @@ static int __bfs(struct lock_list *source_entry,
 		 int forward)
 {
 	struct lock_list *entry;
+	struct lock_list *lock;
 	struct list_head *head;
 	struct circular_queue *cq = &lock_cq;
 	int ret = 1;
@@ -1397,10 +1405,7 @@ static int __bfs(struct lock_list *source_entry,
 	__cq_init(cq);
 	__cq_enqueue(cq, source_entry);
 
-	while (!__cq_empty(cq)) {
-		struct lock_list *lock;
-
-		__cq_dequeue(cq, &lock);
+	while ((lock = __cq_dequeue(cq))) {
 
 		if (!lock->class) {
 			ret = -2;
-- 
1.8.3.1