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Commit aa480771 authored by Yuyang Du's avatar Yuyang Du Committed by Ingo Molnar
Browse files

locking/lockdep: Change type of the element field in circular_queue 



The element field is an array in struct circular_queue to keep track of locks
in the search. Making it the same type as the locks avoids type cast. Also
fix a typo and elaborate the comment above struct circular_queue.

No functional change.

Signed-off-by: default avatarYuyang Du <duyuyang@gmail.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarBart Van Assche <bvanassche@acm.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: frederic@kernel.org
Cc: ming.lei@redhat.com
Cc: will.deacon@arm.com
Link: https://lkml.kernel.org/r/20190506081939.74287-13-duyuyang@gmail.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 31a490e5

kernel/locking/lockdep.c

+14 −10
Original line number Diff line number Diff line
@@ -1262,13 +1262,17 @@ static int add_lock_to_list(struct lock_class *this, 
#define CQ_MASK				(MAX_CIRCULAR_QUEUE_SIZE-1)



/*

 * The circular_queue and helpers is used to implement the

 * breadth-first search(BFS)algorithem, by which we can build

 * the shortest path from the next lock to be acquired to the

 * previous held lock if there is a circular between them.

 * The circular_queue and helpers are used to implement graph

 * breadth-first search (BFS) algorithm, by which we can determine

 * whether there is a path from a lock to another. In deadlock checks,

 * a path from the next lock to be acquired to a previous held lock

 * indicates that adding the <prev> -> <next> lock dependency will

 * produce a circle in the graph. Breadth-first search instead of

 * depth-first search is used in order to find the shortest (circular)

 * path.

 */

struct circular_queue {

	unsigned long element[MAX_CIRCULAR_QUEUE_SIZE];

	struct lock_list *element[MAX_CIRCULAR_QUEUE_SIZE];

	unsigned int  front, rear;

};
@@ -1294,7 +1298,7 @@ static inline int __cq_full(struct circular_queue *cq) 
	return ((cq->rear + 1) & CQ_MASK) == cq->front;

}



static inline int __cq_enqueue(struct circular_queue *cq, unsigned long elem)

static inline int __cq_enqueue(struct circular_queue *cq, struct lock_list *elem)

{

	if (__cq_full(cq))

		return -1;
@@ -1304,7 +1308,7 @@ static inline int __cq_enqueue(struct circular_queue *cq, unsigned long elem) 
	return 0;

}



static inline int __cq_dequeue(struct circular_queue *cq, unsigned long *elem)

static inline int __cq_dequeue(struct circular_queue *cq, struct lock_list **elem)

{

	if (__cq_empty(cq))

		return -1;
@@ -1382,12 +1386,12 @@ static int __bfs(struct lock_list *source_entry, 
		goto exit;



	__cq_init(cq);

	__cq_enqueue(cq, (unsigned long)source_entry);

	__cq_enqueue(cq, source_entry);



	while (!__cq_empty(cq)) {

		struct lock_list *lock;



		__cq_dequeue(cq, (unsigned long *)&lock);

		__cq_dequeue(cq, &lock);



		if (!lock->class) {

			ret = -2;
@@ -1411,7 +1415,7 @@ static int __bfs(struct lock_list *source_entry, 
					goto exit;

				}



				if (__cq_enqueue(cq, (unsigned long)entry)) {

				if (__cq_enqueue(cq, entry)) {

					ret = -1;

					goto exit;

				}