linux-kernel - [PATCH v2 16/19] locking/lockdep: Use function pointer to avoid constant checks

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Date:   Mon, 18 Mar 2019 16:57:30 +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, Yuyang Du <duyuyang@...il.com>
Subject: [PATCH v2 16/19] locking/lockdep: Use function pointer to avoid constant checks

In search of a dependency in the lock graph, there is contant check for
forward or backward search. Use a function pointer to avoid that check.

No functional change.

Signed-off-by: Yuyang Du <duyuyang@...il.com>
---
 kernel/locking/lockdep.c | 27 +++++++++++++++------------
 1 file changed, 15 insertions(+), 12 deletions(-)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index ee8fe64..3dbb4d0 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -1374,11 +1374,21 @@ static inline int get_lock_depth(struct lock_list *child)
 	return depth;
 }
 
+static inline struct list_head *get_forward_dep(struct lock_list * lock)
+{
+	return &lock->class->locks_after;
+}
+
+static inline struct list_head *get_backward_dep(struct lock_list * lock)
+{
+	return &lock->class->locks_before;
+}
+
 static int __bfs(struct lock_list *source_entry,
 		 void *data,
 		 int (*match)(struct lock_list *entry, void *data),
 		 struct lock_list **target_entry,
-		 int forward)
+		 struct list_head *(*get_dep)(struct lock_list * lock))
 {
 	struct lock_list *entry;
 	struct lock_list *lock;
@@ -1392,11 +1402,7 @@ static int __bfs(struct lock_list *source_entry,
 		goto exit;
 	}
 
-	if (forward)
-		head = &source_entry->class->locks_after;
-	else
-		head = &source_entry->class->locks_before;
-
+	head = get_dep(source_entry);
 	if (list_empty(head))
 		goto exit;
 
@@ -1410,10 +1416,7 @@ static int __bfs(struct lock_list *source_entry,
 			goto exit;
 		}
 
-		if (forward)
-			head = &lock->class->locks_after;
-		else
-			head = &lock->class->locks_before;
+		head = get_dep(lock);
 
 		DEBUG_LOCKS_WARN_ON(!irqs_disabled());
 
@@ -1445,7 +1448,7 @@ static inline int __bfs_forwards(struct lock_list *src_entry, void *data,
 				 int (*match)(struct lock_list *entry, void *data),
 				 struct lock_list **target_entry)
 {
-	return __bfs(src_entry, data, match, target_entry, 1);
+	return __bfs(src_entry, data, match, target_entry, get_forward_dep);
 
 }
 
@@ -1453,7 +1456,7 @@ static inline int __bfs_backwards(struct lock_list *src_entry, void *data,
 				  int (*match)(struct lock_list *entry, void *data),
 				  struct lock_list **target_entry)
 {
-	return __bfs(src_entry, data, match, target_entry, 0);
+	return __bfs(src_entry, data, match, target_entry, get_backward_dep);
 
 }
 
-- 
1.8.3.1