linux-kernel - [PATCH v8 03/14] lockdep: Change the meaning of check_prev

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Date:   Mon,  7 Aug 2017 16:12:50 +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, akpm@...ux-foundation.org, willy@...radead.org,
        npiggin@...il.com, kernel-team@....com
Subject: [PATCH v8 03/14] 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 9d16723..b23e930 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -1870,7 +1870,7 @@ static inline void inc_chains(void)
 		if (entry->class == hlock_class(next)) {
 			if (distance == 1)
 				entry->distance = 1;
-			return 2;
+			return 1;
 		}
 	}
 
@@ -1910,9 +1910,10 @@ 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