linux-kernel - [PATCH v2 19/19] locking/lockdep: Change if to else-if when checking bfs errors

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Date:   Mon, 18 Mar 2019 16:57:33 +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 19/19] locking/lockdep: Change if to else-if when checking bfs errors

After BFS searching, we check whether there is an error. These checks are
exclusive, so we can use "else if" instead of "if", which results in a bit
optimized code.

No functional change.

Signed-off-by: Yuyang Du <duyuyang@...il.com>
---
 kernel/locking/lockdep.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 1d38bf6..3efc00e 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -1950,21 +1950,21 @@ static void print_lock_class_header(struct lock_class *class, int depth)
 
 	this.class = hlock_class(prev);
 	ret = find_usage_backwards(&this, bit_backwards, &target_entry);
-	if (ret < 0) {
+	if (unlikely(ret < 0)) {
 		print_bfs_bug(ret);
 		return 0;
 	}
-	if (ret == 1)
+	else if (ret == 1)
 		return ret;
 
 	that.parent = NULL;
 	that.class = hlock_class(next);
 	ret = find_usage_forwards(&that, bit_forwards, &target_entry1);
-	if (ret < 0) {
+	if (unlikely(ret < 0)) {
 		print_bfs_bug(ret);
 		return 0;
 	}
-	if (ret == 1)
+	else if (ret == 1)
 		return ret;
 
 	print_bad_irq_dependency(curr, &this, &that,
@@ -2282,7 +2282,7 @@ static void print_deadlock_scenario(struct held_lock *nxt,
 		debug_atomic_inc(nr_redundant);
 		return 2;
 	}
-	if (ret < 0) {
+	else if (unlikely(ret < 0)) {
 		print_bfs_bug(ret);
 		return 0;
 	}
@@ -2967,11 +2967,11 @@ static int mark_lock(struct task_struct *curr, struct held_lock *this,
 	root.parent = NULL;
 	root.class = hlock_class(this);
 	ret = find_usage_forwards(&root, bit, &target_entry);
-	if (ret < 0) {
+	if (unlikely(ret < 0)) {
 		print_bfs_bug(ret);
 		return 0;
 	}
-	if (ret == 1)
+	else if (ret == 1)
 		return ret;
 
 	print_irq_inversion_bug(curr, &root, target_entry,
@@ -2994,11 +2994,11 @@ static int mark_lock(struct task_struct *curr, struct held_lock *this,
 	root.parent = NULL;
 	root.class = hlock_class(this);
 	ret = find_usage_backwards(&root, bit, &target_entry);
-	if (ret < 0) {
+	if (unlikely(ret < 0)) {
 		print_bfs_bug(ret);
 		return 0;
 	}
-	if (ret == 1)
+	else if (ret == 1)
 		return ret;
 
 	print_irq_inversion_bug(curr, &root, target_entry,
-- 
1.8.3.1