[PATCH] lockdep: prove mutex locking correctness

Use the lock validator framework to prove mutex locking correctness.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

include/linux/mutex-debug.h

@@ -2,6 +2,7 @@
 #define __LINUX_MUTEX_DEBUG_H
 
 #include <linux/linkage.h>
+#include <linux/lockdep.h>
 
 /*
  * Mutexes - debugging helpers:
@@ -10,7 +11,12 @@
 #define __DEBUG_MUTEX_INITIALIZER(lockname)				\
 	, .magic = &lockname
 
-#define mutex_init(sem)		__mutex_init(sem, __FILE__":"#sem)
+#define mutex_init(mutex)						\
+do {									\
+	static struct lock_class_key __key;				\
+									\
+	__mutex_init((mutex), #mutex, &__key);				\
+} while (0)
 
 extern void FASTCALL(mutex_destroy(struct mutex *lock));
 

include/linux/mutex.h

@@ -13,6 +13,7 @@
 #include <linux/list.h>
 #include <linux/spinlock_types.h>
 #include <linux/linkage.h>
+#include <linux/lockdep.h>
 
 #include <asm/atomic.h>
 
@@ -53,6 +54,9 @@ struct mutex {
 	const char 		*name;
 	void			*magic;
 #endif
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+	struct lockdep_map	dep_map;
+#endif
 };
 
 /*
@@ -72,20 +76,34 @@ struct mutex_waiter {
 # include <linux/mutex-debug.h>
 #else
 # define __DEBUG_MUTEX_INITIALIZER(lockname)
-# define mutex_init(mutex)			__mutex_init(mutex, NULL)
+# define mutex_init(mutex) \
+do {							\
+	static struct lock_class_key __key;		\
+							\
+	__mutex_init((mutex), #mutex, &__key);		\
+} while (0)
 # define mutex_destroy(mutex)				do { } while (0)
 #endif
 
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+# define __DEP_MAP_MUTEX_INITIALIZER(lockname) \
+		, .dep_map = { .name = #lockname }
+#else
+# define __DEP_MAP_MUTEX_INITIALIZER(lockname)
+#endif
+
 #define __MUTEX_INITIALIZER(lockname) \
 		{ .count = ATOMIC_INIT(1) \
 		, .wait_lock = SPIN_LOCK_UNLOCKED \
 		, .wait_list = LIST_HEAD_INIT(lockname.wait_list) \
-		__DEBUG_MUTEX_INITIALIZER(lockname) }
+		__DEBUG_MUTEX_INITIALIZER(lockname) \
+		__DEP_MAP_MUTEX_INITIALIZER(lockname) }
 
 #define DEFINE_MUTEX(mutexname) \
 	struct mutex mutexname = __MUTEX_INITIALIZER(mutexname)
 
-extern void fastcall __mutex_init(struct mutex *lock, const char *name);
+extern void __mutex_init(struct mutex *lock, const char *name,
+			 struct lock_class_key *key);
 
 /***
  * mutex_is_locked - is the mutex locked
@@ -104,6 +122,13 @@ static inline int fastcall mutex_is_locked(struct mutex *lock)
  */
 extern void fastcall mutex_lock(struct mutex *lock);
 extern int fastcall mutex_lock_interruptible(struct mutex *lock);
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+extern void mutex_lock_nested(struct mutex *lock, unsigned int subclass);
+#else
+# define mutex_lock_nested(lock, subclass) mutex_lock(lock)
+#endif
+
 /*
  * NOTE: mutex_trylock() follows the spin_trylock() convention,
  *       not the down_trylock() convention!

kernel/mutex-debug.c

@@ -83,12 +83,16 @@ void debug_mutex_unlock(struct mutex *lock)
 	DEBUG_LOCKS_WARN_ON(lock->owner != current_thread_info());
 }
 
-void debug_mutex_init(struct mutex *lock, const char *name)
+void debug_mutex_init(struct mutex *lock, const char *name,
+		      struct lock_class_key *key)
 {
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
 	/*
 	 * Make sure we are not reinitializing a held lock:
 	 */
 	debug_check_no_locks_freed((void *)lock, sizeof(*lock));
+	lockdep_init_map(&lock->dep_map, name, key);
+#endif
 	lock->owner = NULL;
 	lock->magic = lock;
 }

kernel/mutex.c

@@ -39,13 +39,14 @@
  *
  * It is not allowed to initialize an already locked mutex.
  */
-__always_inline void fastcall __mutex_init(struct mutex *lock, const char *name)
+void
+__mutex_init(struct mutex *lock, const char *name, struct lock_class_key *key)
 {
 	atomic_set(&lock->count, 1);
 	spin_lock_init(&lock->wait_lock);
 	INIT_LIST_HEAD(&lock->wait_list);
 
-	debug_mutex_init(lock, name);
+	debug_mutex_init(lock, name, key);
 }
 
 EXPORT_SYMBOL(__mutex_init);
@@ -131,6 +132,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass)
 	spin_lock_mutex(&lock->wait_lock, flags);
 
 	debug_mutex_lock_common(lock, &waiter);
+	mutex_acquire(&lock->dep_map, subclass, 0, _RET_IP_);
 	debug_mutex_add_waiter(lock, &waiter, task->thread_info);
 
 	/* add waiting tasks to the end of the waitqueue (FIFO): */
@@ -158,6 +160,7 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass)
 		if (unlikely(state == TASK_INTERRUPTIBLE &&
 						signal_pending(task))) {
 			mutex_remove_waiter(lock, &waiter, task->thread_info);
+			mutex_release(&lock->dep_map, 1, _RET_IP_);
 			spin_unlock_mutex(&lock->wait_lock, flags);
 
 			debug_mutex_free_waiter(&waiter);
@@ -194,16 +197,28 @@ __mutex_lock_slowpath(atomic_t *lock_count)
 	__mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, 0);
 }
 
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+void __sched
+mutex_lock_nested(struct mutex *lock, unsigned int subclass)
+{
+	might_sleep();
+	__mutex_lock_common(lock, TASK_UNINTERRUPTIBLE, subclass);
+}
+
+EXPORT_SYMBOL_GPL(mutex_lock_nested);
+#endif
+
 /*
  * Release the lock, slowpath:
  */
 static fastcall inline void
-__mutex_unlock_common_slowpath(atomic_t *lock_count)
+__mutex_unlock_common_slowpath(atomic_t *lock_count, int nested)
 {
 	struct mutex *lock = container_of(lock_count, struct mutex, count);
 	unsigned long flags;
 
 	spin_lock_mutex(&lock->wait_lock, flags);
+	mutex_release(&lock->dep_map, nested, _RET_IP_);
 	debug_mutex_unlock(lock);
 
 	/*
@@ -236,7 +251,7 @@ __mutex_unlock_common_slowpath(atomic_t *lock_count)
 static fastcall noinline void
 __mutex_unlock_slowpath(atomic_t *lock_count)
 {
-	__mutex_unlock_common_slowpath(lock_count);
+	__mutex_unlock_common_slowpath(lock_count, 1);
 }
 
 /*
@@ -287,9 +302,10 @@ static inline int __mutex_trylock_slowpath(atomic_t *lock_count)
 	spin_lock_mutex(&lock->wait_lock, flags);
 
 	prev = atomic_xchg(&lock->count, -1);
-	if (likely(prev == 1))
+	if (likely(prev == 1)) {
 		debug_mutex_set_owner(lock, current_thread_info());
-
+		mutex_acquire(&lock->dep_map, 0, 1, _RET_IP_);
+	}
 	/* Set it back to 0 if there are no waiters: */
 	if (likely(list_empty(&lock->wait_list)))
 		atomic_set(&lock->count, 0);

kernel/mutex.h

@@ -22,7 +22,7 @@
 #define debug_mutex_free_waiter(waiter)			do { } while (0)
 #define debug_mutex_add_waiter(lock, waiter, ti)	do { } while (0)
 #define debug_mutex_unlock(lock)			do { } while (0)
-#define debug_mutex_init(lock, name)			do { } while (0)
+#define debug_mutex_init(lock, name, key)		do { } while (0)
 
 static inline void
 debug_mutex_lock_common(struct mutex *lock, struct mutex_waiter *waiter)