linux-kernel - [PATCH v4 03/30] locking/lockdep: Change return type of lookup_chain_cache

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Date:   Thu, 29 Aug 2019 16:31:05 +0800
From:   Yuyang Du <duyuyang@...il.com>
To:     peterz@...radead.org, will.deacon@....com, mingo@...nel.org
Cc:     bvanassche@....org, ming.lei@...hat.com, frederic@...nel.org,
        tglx@...utronix.de, linux-kernel@...r.kernel.org,
        longman@...hat.com, paulmck@...ux.vnet.ibm.com,
        boqun.feng@...il.com, Yuyang Du <duyuyang@...il.com>
Subject: [PATCH v4 03/30] locking/lockdep: Change return type of lookup_chain_cache_add()

Like the previous change, the function lookup_chain_cache_add() returns
the pointer of the lock chain if the chain is new.

No functional change.

Signed-off-by: Yuyang Du <duyuyang@...il.com>
---
 kernel/locking/lockdep.c | 23 ++++++++++-------------
 1 file changed, 10 insertions(+), 13 deletions(-)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 9c9b408..51918d2 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -2870,13 +2870,13 @@ static inline struct lock_chain *lookup_chain_cache(u64 chain_key)
 
 /*
  * If the key is not present yet in dependency chain cache then
- * add it and return 1 - in this case the new dependency chain is
- * validated. If the key is already hashed, return 0.
- * (On return with 1 graph_lock is held.)
+ * add it and return the chain - in this case the new dependency
+ * chain will be validated. If the key is already hashed, return
+ * NULL. (On return with the new chain graph_lock is held.)
  */
-static inline int lookup_chain_cache_add(struct task_struct *curr,
-					 struct held_lock *hlock,
-					 u64 chain_key)
+static inline struct lock_chain *
+lookup_chain_cache_add(struct task_struct *curr, struct held_lock *hlock,
+		       u64 chain_key)
 {
 	struct lock_class *class = hlock_class(hlock);
 	struct lock_chain *chain = lookup_chain_cache(chain_key);
@@ -2884,7 +2884,7 @@ static inline int lookup_chain_cache_add(struct task_struct *curr,
 	if (chain) {
 cache_hit:
 		if (!check_no_collision(curr, hlock, chain))
-			return 0;
+			return NULL;
 
 		if (very_verbose(class)) {
 			printk("\nhash chain already cached, key: "
@@ -2893,7 +2893,7 @@ static inline int lookup_chain_cache_add(struct task_struct *curr,
 					class->key, class->name);
 		}
 
-		return 0;
+		return NULL;
 	}
 
 	if (very_verbose(class)) {
@@ -2902,7 +2902,7 @@ static inline int lookup_chain_cache_add(struct task_struct *curr,
 	}
 
 	if (!graph_lock())
-		return 0;
+		return NULL;
 
 	/*
 	 * We have to walk the chain again locked - to avoid duplicates:
@@ -2913,10 +2913,7 @@ static inline int lookup_chain_cache_add(struct task_struct *curr,
 		goto cache_hit;
 	}
 
-	if (!add_chain_cache(curr, hlock, chain_key))
-		return 0;
-
-	return 1;
+	return add_chain_cache(curr, hlock, chain_key);
 }
 
 static int validate_chain(struct task_struct *curr,
-- 
1.8.3.1