linux-kernel - [PATCH v4 02/30] locking/lockdep: Change return type of add_chain

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Date:   Thu, 29 Aug 2019 16:31:04 +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 02/30] locking/lockdep: Change return type of add_chain_cache()

The function add_chain_cache() adds a new chain - the current lock chain
- into the lock_chains cache if it does not exist in there.

Previously if failed, an integer 0 is returned and if successful, 1 is
returned. Change the return type to the pointer of the chain if the new
chain is added or NULL otherwise for later use.

No functional change.

Signed-off-by: Yuyang Du <duyuyang@...il.com>
---
 kernel/locking/lockdep.c | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 3c89a50..9c9b408 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -2788,12 +2788,12 @@ static struct lock_chain *alloc_lock_chain(void)
  * Adds a dependency chain into chain hashtable. And must be called with
  * graph_lock held.
  *
- * Return 0 if fail, and graph_lock is released.
- * Return 1 if succeed, with graph_lock held.
+ * Return NULL if failed, and graph_lock is released.
+ * Return the new chain if successful, with graph_lock held.
  */
-static inline int add_chain_cache(struct task_struct *curr,
-				  struct held_lock *hlock,
-				  u64 chain_key)
+static inline struct lock_chain *add_chain_cache(struct task_struct *curr,
+						 struct held_lock *hlock,
+						 u64 chain_key)
 {
 	struct lock_class *class = hlock_class(hlock);
 	struct hlist_head *hash_head = chainhashentry(chain_key);
@@ -2806,16 +2806,16 @@ static inline int add_chain_cache(struct task_struct *curr,
 	 * lockdep won't complain about its own locking errors.
 	 */
 	if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
-		return 0;
+		return NULL;
 
 	chain = alloc_lock_chain();
 	if (!chain) {
 		if (!debug_locks_off_graph_unlock())
-			return 0;
+			return NULL;
 
 		print_lockdep_off("BUG: MAX_LOCKDEP_CHAINS too low!");
 		dump_stack();
-		return 0;
+		return NULL;
 	}
 	chain->chain_key = chain_key;
 	chain->irq_context = hlock->irq_context;
@@ -2836,18 +2836,18 @@ static inline int add_chain_cache(struct task_struct *curr,
 		nr_chain_hlocks += chain->depth;
 	} else {
 		if (!debug_locks_off_graph_unlock())
-			return 0;
+			return NULL;
 
 		print_lockdep_off("BUG: MAX_LOCKDEP_CHAIN_HLOCKS too low!");
 		dump_stack();
-		return 0;
+		return NULL;
 	}
 
 	hlist_add_head_rcu(&chain->entry, hash_head);
 	debug_atomic_inc(chain_lookup_misses);
 	inc_chains();
 
-	return 1;
+	return chain;
 }
 
 /*
-- 
1.8.3.1