linux-kernel - [tip:locking/core] locking/lockdep: Change the meaning of check_prev

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Date:   Thu, 10 Aug 2017 05:19:12 -0700
From:   tip-bot for Byungchul Park <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     hpa@...or.com, mingo@...nel.org, tglx@...utronix.de,
        torvalds@...ux-foundation.org, byungchul.park@....com,
        linux-kernel@...r.kernel.org, peterz@...radead.org
Subject: [tip:locking/core] locking/lockdep: Change the meaning of
 check_prev_add()'s return value

Commit-ID:  70911fdc9576f4eeb3986689a1c9a778a4a4aacb
Gitweb:     http://git.kernel.org/tip/70911fdc9576f4eeb3986689a1c9a778a4a4aacb
Author:     Byungchul Park <byungchul.park@....com>
AuthorDate: Mon, 7 Aug 2017 16:12:50 +0900
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Thu, 10 Aug 2017 12:29:06 +0200

locking/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>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: akpm@...ux-foundation.org
Cc: boqun.feng@...il.com
Cc: kernel-team@....com
Cc: kirill@...temov.name
Cc: npiggin@...il.com
Cc: walken@...gle.com
Cc: willy@...radead.org
Link: http://lkml.kernel.org/r/1502089981-21272-4-git-send-email-byungchul.park@lge.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 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 bdf6b31..7cf02fa 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -1881,7 +1881,7 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev,
 		if (entry->class == hlock_class(next)) {
 			if (distance == 1)
 				entry->distance = 1;
-			return 2;
+			return 1;
 		}
 	}
 
@@ -1935,9 +1935,10 @@ check_prev_add(struct task_struct *curr, struct held_lock *prev,
 		print_lock_name(hlock_class(next));
 		printk(KERN_CONT "\n");
 		dump_stack();
-		return graph_lock();
+		if (!graph_lock())
+			return 0;
 	}
-	return 1;
+	return 2;
 }
 
 /*