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

Tetsuo Handa · Ingo Molnar · commit 76e64c73db95 · 2022-09-21T09:58:21.000+02:00
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 torvalds#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@I-love.SAKURA.ne.jp> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lore.kernel.org/r/bd99391e-f787-efe9-5ec6-3c6dc4c587b0@I-love.SAKURA.ne.jp
diff --git 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;
 		}
 	}

Original file line number	Diff line number	Diff line change
`@@ -934,8 +934,10 @@ look_up_lock_class(const struct lockdep_map *lock, unsigned int subclass)`
`934`	`934`	`* Huh! same key, different name? Did someone trample`
`935`	`935`	`* on some memory? We're most confused.`
`936`	`936`	`*/`
`937`		`- WARN_ON_ONCE(class->name != lock->name &&`
`938`		`- lock->key != &__lockdep_no_validate__);`
	`937`	`+ WARN_ONCE(class->name != lock->name &&`
	`938`	`+ lock->key != &__lockdep_no_validate__,`
	`939`	`+ "Looking for class \"%s\" with key %ps, but found a different class \"%s\" with the same key\n",`
	`940`	`+ lock->name, lock->key, class->name);`
`939`	`941`	`return class;`
`940`	`942`	`}`
`941`	`943`	`}`