linux-kernel - [PATCH v2 2/3] locking/lockdep: Unlikely conditons about BFS

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Date:   Fri, 18 Jun 2021 22:55:33 +0800
From:   Xiongwei Song <sxwjean@...com>
To:     peterz@...radead.org, mingo@...hat.com, will@...nel.org,
        longman@...hat.com, boqun.feng@...il.com
Cc:     linux-kernel@...r.kernel.org, Xiongwei Song <sxwjean@...il.com>
Subject: [PATCH v2 2/3] locking/lockdep: Unlikely conditons about BFS_RMATCH

From: Xiongwei Song <sxwjean@...il.com>

The probability that graph walk will return BFS_RMATCH is slim, so unlikey
conditons about BFS_RMATCH can improve performance a little bit.

Signed-off-by: Xiongwei Song <sxwjean@...il.com>
---
 kernel/locking/lockdep.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index a8a66a2a9bc1..cb94097014d8 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -2750,7 +2750,7 @@ check_redundant(struct held_lock *src, struct held_lock *target)
 	 */
 	ret = check_path(target, &src_entry, hlock_equal, usage_skip, &target_entry);
 
-	if (ret == BFS_RMATCH)
+	if (unlikely(ret == BFS_RMATCH))
 		debug_atomic_inc(nr_redundant);
 
 	return ret;
@@ -2992,7 +2992,7 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev,
 	ret = check_redundant(prev, next);
 	if (bfs_error(ret))
 		return 0;
-	else if (ret == BFS_RMATCH)
+	else if (unlikely(ret == BFS_RMATCH))
 		return 2;
 
 	if (!*trace) {
-- 
2.30.2