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@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: bvanassche@acm.org
Cc: frederic@kernel.org
Cc: ming.lei@redhat.com
Cc: will.deacon@arm.com
Link: https://lkml.kernel.org/r/20190506081939.74287-14-duyuyang@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 13 insertions, 8 deletions

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index d467ba825dca..d23dcb47389e 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -1308,14 +1308,21 @@ 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 a lock_list 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)
@@ -1367,6 +1374,7 @@ 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;
@@ -1388,10 +1396,7 @@ 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;