linux-kernel - [PATCH v3 09/30] locking/lockdep: Remove chain_head argument in validate

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Date:   Fri, 28 Jun 2019 17:15:07 +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 v3 09/30] locking/lockdep: Remove chain_head argument in validate_chain()

This argument says whether the chain is a head, meaning having just one
lock, which can actually be tested by lock_chain->depth. So there is no
need to explicitly make this argument, so remove it.

No functional change.

Signed-off-by: Yuyang Du <duyuyang@...il.com>
---
 kernel/locking/lockdep.c | 18 +++++++-----------
 1 file changed, 7 insertions(+), 11 deletions(-)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 4ffb4df..e2ad673 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -2807,9 +2807,8 @@ static inline struct lock_chain *lookup_chain_cache(u64 chain_key)
 	return add_chain_cache(curr, hlock, chain_key);
 }
 
-static int validate_chain(struct task_struct *curr,
-			  struct held_lock *hlock,
-			  int chain_head, u64 chain_key)
+static int validate_chain(struct task_struct *curr, struct held_lock *hlock,
+			  u64 chain_key)
 {
 	struct lock_chain *chain;
 	/*
@@ -2857,7 +2856,7 @@ static int validate_chain(struct task_struct *curr,
 		 * Add dependency only if this lock is not the head
 		 * of the chain, and if it's not a secondary read-lock:
 		 */
-		if (!chain_head && ret != 2) {
+		if (chain->depth > 1 && ret != 2) {
 			if (!check_prevs_add(curr, hlock, chain))
 				return 0;
 		}
@@ -2874,7 +2873,7 @@ static int validate_chain(struct task_struct *curr,
 #else
 static inline int validate_chain(struct task_struct *curr,
 				 struct held_lock *hlock,
-				 int chain_head, u64 chain_key)
+				 u64 chain_key)
 {
 	return 1;
 }
@@ -3707,7 +3706,6 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
 	struct lock_class *class = NULL;
 	struct held_lock *hlock;
 	unsigned int depth;
-	int chain_head = 0;
 	int class_idx;
 	u64 chain_key;
 
@@ -3821,14 +3819,12 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
 		 */
 		if (DEBUG_LOCKS_WARN_ON(chain_key != INITIAL_CHAIN_KEY))
 			return 0;
-		chain_head = 1;
 	}
 
 	hlock->prev_chain_key = chain_key;
-	if (separate_irq_context(curr, hlock)) {
+	if (separate_irq_context(curr, hlock))
 		chain_key = INITIAL_CHAIN_KEY;
-		chain_head = 1;
-	}
+
 	chain_key = iterate_chain_key(chain_key, class_idx);
 
 	if (nest_lock && !__lock_is_held(nest_lock, -1)) {
@@ -3841,7 +3837,7 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
 		WARN_ON_ONCE(!hlock_class(hlock)->key);
 	}
 
-	if (!validate_chain(curr, hlock, chain_head, chain_key))
+	if (!validate_chain(curr, hlock, chain_key))
 		return 0;
 
 	curr->curr_chain_key = chain_key;
-- 
1.8.3.1