linux-kernel - [tip: locking/core] locking/lockdep: Print more debug information - report name and key when look_up_lock

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Date:   Wed, 21 Sep 2022 08:01:26 -0000
From:   "tip-bot2 for Tetsuo Handa" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
        Ingo Molnar <mingo@...nel.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: locking/core] locking/lockdep: Print more debug information -
 report name and key when look_up_lock_class() got confused

The following commit has been merged into the locking/core branch of tip:

Commit-ID:     76e64c73db9542ff4bae8a60f4f32e38f3799b95
Gitweb:        https://git.kernel.org/tip/76e64c73db9542ff4bae8a60f4f32e38f3799b95
Author:        Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
AuthorDate:    Mon, 19 Sep 2022 09:52:13 +09:00
Committer:     Ingo Molnar <mingo@...nel.org>
CommitterDate: Wed, 21 Sep 2022 09:58:21 +02:00

locking/lockdep: Print more debug information - report name and key when look_up_lock_class() got confused

Printing this information will be helpful:

  ------------[ cut here ]------------
  Looking for class "l2tp_sock" with key l2tp_socket_class, but found a different class "slock-AF_INET6" with the same key
  WARNING: CPU: 1 PID: 14195 at kernel/locking/lockdep.c:940 look_up_lock_class+0xcc/0x140
  Modules linked in:
  CPU: 1 PID: 14195 Comm: a.out Not tainted 6.0.0-rc6-dirty #863
  Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006
  RIP: 0010:look_up_lock_class+0xcc/0x140

Signed-off-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Link: https://lore.kernel.org/r/bd99391e-f787-efe9-5ec6-3c6dc4c587b0@I-love.SAKURA.ne.jp
---
 kernel/locking/lockdep.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 64a13eb..e3375bc 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -934,8 +934,10 @@ look_up_lock_class(const struct lockdep_map *lock, unsigned int subclass)
 			 * Huh! same key, different name? Did someone trample
 			 * on some memory? We're most confused.
 			 */
-			WARN_ON_ONCE(class->name != lock->name &&
-				     lock->key != &__lockdep_no_validate__);
+			WARN_ONCE(class->name != lock->name &&
+				  lock->key != &__lockdep_no_validate__,
+				  "Looking for class \"%s\" with key %ps, but found a different class \"%s\" with the same key\n",
+				  lock->name, lock->key, class->name);
 			return class;
 		}
 	}