linux-kernel - [PATCH v6 03/15] lockdep: Change the meaning of check_prev

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Message-ID: <1489479542-27030-4-git-send-email-byungchul.park@lge.com>
Date:   Tue, 14 Mar 2017 17:18:50 +0900
From:   Byungchul Park <byungchul.park@....com>
To:     <peterz@...radead.org>, <mingo@...nel.org>
CC:     <tglx@...utronix.de>, <walken@...gle.com>, <boqun.feng@...il.com>,
        <kirill@...temov.name>, <linux-kernel@...r.kernel.org>,
        <linux-mm@...ck.org>, <iamjoonsoo.kim@....com>,
        <akpm@...ux-foundation.org>, <willy@...radead.org>,
        <npiggin@...il.com>, <kernel-team@....com>
Subject: [PATCH v6 03/15] lockdep: Change the meaning of check_prev_add()'s return value

Firstly, return 1 instead of 2 when 'prev -> next' dependency already
exists. Since the value 2 is not referenced anywhere, just return 1
indicating success in this case.

Secondly, return 2 instead of 1 when successfully added a lock_list
entry with saving stack_trace. With that, a caller can decide whether
to avoid redundant save_trace() on the caller site.

Signed-off-by: Byungchul Park <byungchul.park@....com>
---
 kernel/locking/lockdep.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index eb39474..4709110 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -1854,7 +1854,7 @@ static inline void inc_chains(void)
 		if (entry->class == hlock_class(next)) {
 			if (distance == 1)
 				entry->distance = 1;
-			return 2;
+			return 1;
 		}
 	}
 
@@ -1894,9 +1894,10 @@ static inline void inc_chains(void)
 		print_lock_name(hlock_class(next));
 		printk(KERN_CONT "\n");
 		dump_stack();
-		return graph_lock();
+		if (!graph_lock())
+			return 0;
 	}
-	return 1;
+	return 2;
 }
 
 /*
-- 
1.9.1