linux-kernel - [PATCH for 2.6.24] fix workqueue creation API lockdep interaction

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 15 Jan 2008 14:04:31 +0100
From:	Johannes Berg <johannes@...solutions.net>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Dave Young <hidave.darkstar@...il.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>, Oleg Nesterov <oleg@...sign.ru>
Subject: [PATCH for 2.6.24] fix workqueue creation API lockdep interaction

Dave Young reported warnings from lockdep that the workqueue API
can sometimes try to register lockdep classes with the same key
but different names. This is not permitted in lockdep.

Unfortunately, I was unaware of that restriction when I wrote
the code to debug workqueue problems with lockdep and used the
workqueue name as the lockdep class name. This can obviously
lead to the problem if the workqueue name is dynamic.

This patch solves the problem by always using a constant name
for the workqueue's lockdep class, namely either the constant
name that was passed in or a string consisting of the variable
name.

Signed-off-by: Johannes Berg <johannes@...solutions.net>
---
Please be careful with this patch, I haven't been able to test it so far
because my powerbook doesn't have lockdep.

 include/linux/workqueue.h |   14 +++++++++++---
 kernel/workqueue.c        |    5 +++--
 2 files changed, 14 insertions(+), 5 deletions(-)

--- everything.orig/include/linux/workqueue.h	2008-01-15 02:10:55.098131131 +0100
+++ everything/include/linux/workqueue.h	2008-01-15 02:26:37.428130426 +0100
@@ -149,19 +149,27 @@ struct execute_work {
 
 extern struct workqueue_struct *
 __create_workqueue_key(const char *name, int singlethread,
-		       int freezeable, struct lock_class_key *key);
+		       int freezeable, struct lock_class_key *key,
+		       const char *lock_name);
 
 #ifdef CONFIG_LOCKDEP
 #define __create_workqueue(name, singlethread, freezeable)	\
 ({								\
 	static struct lock_class_key __key;			\
+	const char *__lock_name;				\
+								\
+	if (__builtin_constant_p(name))				\
+		__lock_name = (name);				\
+	else							\
+		__lock_name = #name;				\
 								\
 	__create_workqueue_key((name), (singlethread),		\
-			       (freezeable), &__key);		\
+			       (freezeable), &__key,		\
+			       __lock_name);			\
 })
 #else
 #define __create_workqueue(name, singlethread, freezeable)	\
-	__create_workqueue_key((name), (singlethread), (freezeable), NULL)
+	__create_workqueue_key((name), (singlethread), (freezeable), NULL, NULL)
 #endif
 
 #define create_workqueue(name) __create_workqueue((name), 0, 0)
--- everything.orig/kernel/workqueue.c	2008-01-15 02:15:13.578132867 +0100
+++ everything/kernel/workqueue.c	2008-01-15 02:18:40.518138455 +0100
@@ -722,7 +722,8 @@ static void start_workqueue_thread(struc
 struct workqueue_struct *__create_workqueue_key(const char *name,
 						int singlethread,
 						int freezeable,
-						struct lock_class_key *key)
+						struct lock_class_key *key,
+						const char *lock_name)
 {
 	struct workqueue_struct *wq;
 	struct cpu_workqueue_struct *cwq;
@@ -739,7 +740,7 @@ struct workqueue_struct *__create_workqu
 	}
 
 	wq->name = name;
-	lockdep_init_map(&wq->lockdep_map, name, key, 0);
+	lockdep_init_map(&wq->lockdep_map, lock_name, key, 0);
 	wq->singlethread = singlethread;
 	wq->freezeable = freezeable;
 	INIT_LIST_HEAD(&wq->list);


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/