[PATCH] lockdep: prove rwsem locking correctness

Use the lock validator framework to prove rwsem locking correctness.
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NArjan van de Ven <arjan@linux.intel.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

include/asm-i386/rwsem.h

@@ -40,6 +40,7 @@
 
 #include <linux/list.h>
 #include <linux/spinlock.h>
+#include <linux/lockdep.h>
 
 struct rwsem_waiter;
 
@@ -61,21 +62,34 @@ struct rw_semaphore {
 #define RWSEM_ACTIVE_WRITE_BIAS		(RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
 	spinlock_t		wait_lock;
 	struct list_head	wait_list;
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+	struct lockdep_map dep_map;
+#endif
 };
 
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+# define __RWSEM_DEP_MAP_INIT(lockname) , .dep_map = { .name = #lockname }
+#else
+# define __RWSEM_DEP_MAP_INIT(lockname)
+#endif
+
+
 #define __RWSEM_INITIALIZER(name) \
 { RWSEM_UNLOCKED_VALUE, SPIN_LOCK_UNLOCKED, LIST_HEAD_INIT((name).wait_list) \
-	}
+	__RWSEM_DEP_MAP_INIT(name) }
 
 #define DECLARE_RWSEM(name) \
 	struct rw_semaphore name = __RWSEM_INITIALIZER(name)
 
-static inline void init_rwsem(struct rw_semaphore *sem)
-{
-	sem->count = RWSEM_UNLOCKED_VALUE;
-	spin_lock_init(&sem->wait_lock);
-	INIT_LIST_HEAD(&sem->wait_list);
-}
+extern void __init_rwsem(struct rw_semaphore *sem, const char *name,
+			 struct lock_class_key *key);
+
+#define init_rwsem(sem)						\
+do {								\
+	static struct lock_class_key __key;			\
+								\
+	__init_rwsem((sem), #sem, &__key);			\
+} while (0)
 
 /*
  * lock for reading
@@ -128,7 +142,7 @@ LOCK_PREFIX	"  cmpxchgl  %2,%0\n\t"
 /*
  * lock for writing
  */
-static inline void __down_write(struct rw_semaphore *sem)
+static inline void __down_write_nested(struct rw_semaphore *sem, int subclass)
 {
 	int tmp;
 
@@ -152,6 +166,11 @@ LOCK_PREFIX	"  xadd      %%edx,(%%eax)\n\t" /* subtract 0x0000ffff, returns the
 		: "memory", "cc");
 }
 
+static inline void __down_write(struct rw_semaphore *sem)
+{
+	__down_write_nested(sem, 0);
+}
+
 /*
  * trylock for writing -- returns 1 if successful, 0 if contention
  */

include/asm-s390/rwsem.h

@@ -61,6 +61,9 @@ struct rw_semaphore {
 	signed long		count;
 	spinlock_t		wait_lock;
 	struct list_head	wait_list;
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+	struct lockdep_map	dep_map;
+#endif
 };
 
 #ifndef __s390x__
@@ -80,8 +83,16 @@ struct rw_semaphore {
 /*
  * initialisation
  */
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+# define __RWSEM_DEP_MAP_INIT(lockname) , .dep_map = { .name = #lockname }
+#else
+# define __RWSEM_DEP_MAP_INIT(lockname)
+#endif
+
 #define __RWSEM_INITIALIZER(name) \
-{ RWSEM_UNLOCKED_VALUE, SPIN_LOCK_UNLOCKED, LIST_HEAD_INIT((name).wait_list) }
+{ RWSEM_UNLOCKED_VALUE, SPIN_LOCK_UNLOCKED, LIST_HEAD_INIT((name).wait_list) \
+  __RWSEM_DEP_MAP_INIT(name) }
 
 #define DECLARE_RWSEM(name) \
 	struct rw_semaphore name = __RWSEM_INITIALIZER(name)
@@ -93,6 +104,17 @@ static inline void init_rwsem(struct rw_semaphore *sem)
 	INIT_LIST_HEAD(&sem->wait_list);
 }
 
+extern void __init_rwsem(struct rw_semaphore *sem, const char *name,
+			 struct lock_class_key *key);
+
+#define init_rwsem(sem)				\
+do {						\
+	static struct lock_class_key __key;	\
+						\
+	__init_rwsem((sem), #sem, &__key);	\
+} while (0)
+
+
 /*
  * lock for reading
  */
@@ -155,7 +177,7 @@ static inline int __down_read_trylock(struct rw_semaphore *sem)
 /*
  * lock for writing
  */
-static inline void __down_write(struct rw_semaphore *sem)
+static inline void __down_write_nested(struct rw_semaphore *sem, int subclass)
 {
 	signed long old, new, tmp;
 
@@ -181,6 +203,11 @@ static inline void __down_write(struct rw_semaphore *sem)
 		rwsem_down_write_failed(sem);
 }
 
+static inline void __down_write(struct rw_semaphore *sem)
+{
+	__down_write_nested(sem, 0);
+}
+
 /*
  * trylock for writing -- returns 1 if successful, 0 if contention
  */

include/asm-s390/semaphore.h

@@ -37,7 +37,8 @@ struct semaphore {
 
 static inline void sema_init (struct semaphore *sem, int val)
 {
-	*sem = (struct semaphore) __SEMAPHORE_INITIALIZER((*sem),val);
+	atomic_set(&sem->count, val);
+	init_waitqueue_head(&sem->wait);
 }
 
 static inline void init_MUTEX (struct semaphore *sem)

include/linux/rwsem-spinlock.h

@@ -32,18 +32,37 @@ struct rw_semaphore {
 	__s32			activity;
 	spinlock_t		wait_lock;
 	struct list_head	wait_list;
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+	struct lockdep_map dep_map;
+#endif
 };
 
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+# define __RWSEM_DEP_MAP_INIT(lockname) , .dep_map = { .name = #lockname }
+#else
+# define __RWSEM_DEP_MAP_INIT(lockname)
+#endif
+
 #define __RWSEM_INITIALIZER(name) \
-{ 0, SPIN_LOCK_UNLOCKED, LIST_HEAD_INIT((name).wait_list) }
+{ 0, SPIN_LOCK_UNLOCKED, LIST_HEAD_INIT((name).wait_list) __RWSEM_DEP_MAP_INIT(name) }
 
 #define DECLARE_RWSEM(name) \
 	struct rw_semaphore name = __RWSEM_INITIALIZER(name)
 
-extern void FASTCALL(init_rwsem(struct rw_semaphore *sem));
+extern void __init_rwsem(struct rw_semaphore *sem, const char *name,
+			 struct lock_class_key *key);
+
+#define init_rwsem(sem)						\
+do {								\
+	static struct lock_class_key __key;			\
+								\
+	__init_rwsem((sem), #sem, &__key);			\
+} while (0)
+
 extern void FASTCALL(__down_read(struct rw_semaphore *sem));
 extern int FASTCALL(__down_read_trylock(struct rw_semaphore *sem));
 extern void FASTCALL(__down_write(struct rw_semaphore *sem));
+extern void FASTCALL(__down_write_nested(struct rw_semaphore *sem, int subclass));
 extern int FASTCALL(__down_write_trylock(struct rw_semaphore *sem));
 extern void FASTCALL(__up_read(struct rw_semaphore *sem));
 extern void FASTCALL(__up_write(struct rw_semaphore *sem));

include/linux/rwsem.h

@@ -27,64 +27,55 @@ struct rw_semaphore;
 /*
  * lock for reading
  */
-static inline void down_read(struct rw_semaphore *sem)
-{
-	might_sleep();
-	__down_read(sem);
-}
+extern void down_read(struct rw_semaphore *sem);
 
 /*
  * trylock for reading -- returns 1 if successful, 0 if contention
  */
-static inline int down_read_trylock(struct rw_semaphore *sem)
-{
-	int ret;
-	ret = __down_read_trylock(sem);
-	return ret;
-}
+extern int down_read_trylock(struct rw_semaphore *sem);
 
 /*
  * lock for writing
  */
-static inline void down_write(struct rw_semaphore *sem)
-{
-	might_sleep();
-	__down_write(sem);
-}
+extern void down_write(struct rw_semaphore *sem);
 
 /*
  * trylock for writing -- returns 1 if successful, 0 if contention
  */
-static inline int down_write_trylock(struct rw_semaphore *sem)
-{
-	int ret;
-	ret = __down_write_trylock(sem);
-	return ret;
-}
+extern int down_write_trylock(struct rw_semaphore *sem);
 
 /*
  * release a read lock
  */
-static inline void up_read(struct rw_semaphore *sem)
-{
-	__up_read(sem);
-}
+extern void up_read(struct rw_semaphore *sem);
 
 /*
  * release a write lock
  */
-static inline void up_write(struct rw_semaphore *sem)
-{
-	__up_write(sem);
-}
+extern void up_write(struct rw_semaphore *sem);
 
 /*
  * downgrade write lock to read lock
  */
-static inline void downgrade_write(struct rw_semaphore *sem)
-{
-	__downgrade_write(sem);
-}
+extern void downgrade_write(struct rw_semaphore *sem);
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+/*
+ * nested locking:
+ */
+extern void down_read_nested(struct rw_semaphore *sem, int subclass);
+extern void down_write_nested(struct rw_semaphore *sem, int subclass);
+/*
+ * Take/release a lock when not the owner will release it:
+ */
+extern void down_read_non_owner(struct rw_semaphore *sem);
+extern void up_read_non_owner(struct rw_semaphore *sem);
+#else
+# define down_read_nested(sem, subclass)		down_read(sem)
+# define down_write_nested(sem, subclass)	down_write(sem)
+# define down_read_non_owner(sem)		down_read(sem)
+# define up_read_non_owner(sem)			up_read(sem)
+#endif
 
 #endif /* __KERNEL__ */
 #endif /* _LINUX_RWSEM_H */

kernel/Makefile

@@ -8,7 +8,7 @@ obj-y     = sched.o fork.o exec_domain.o panic.o printk.o profile.o \
 	    signal.o sys.o kmod.o workqueue.o pid.o \
 	    rcupdate.o extable.o params.o posix-timers.o \
 	    kthread.o wait.o kfifo.o sys_ni.o posix-cpu-timers.o mutex.o \
-	    hrtimer.o
+	    hrtimer.o rwsem.o
 
 obj-$(CONFIG_STACKTRACE) += stacktrace.o
 obj-y += time/

kernel/rwsem.c

@@ -103,3 +103,45 @@ void downgrade_write(struct rw_semaphore *sem)
 }
 
 EXPORT_SYMBOL(downgrade_write);
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+
+void down_read_nested(struct rw_semaphore *sem, int subclass)
+{
+	might_sleep();
+	rwsem_acquire_read(&sem->dep_map, subclass, 0, _RET_IP_);
+
+	__down_read(sem);
+}
+
+EXPORT_SYMBOL(down_read_nested);
+
+void down_read_non_owner(struct rw_semaphore *sem)
+{
+	might_sleep();
+
+	__down_read(sem);
+}
+
+EXPORT_SYMBOL(down_read_non_owner);
+
+void down_write_nested(struct rw_semaphore *sem, int subclass)
+{
+	might_sleep();
+	rwsem_acquire(&sem->dep_map, subclass, 0, _RET_IP_);
+
+	__down_write_nested(sem, subclass);
+}
+
+EXPORT_SYMBOL(down_write_nested);
+
+void up_read_non_owner(struct rw_semaphore *sem)
+{
+	__up_read(sem);
+}
+
+EXPORT_SYMBOL(up_read_non_owner);
+
+#endif
+
+

lib/rwsem-spinlock.c

@@ -20,8 +20,16 @@ struct rwsem_waiter {
 /*
  * initialise the semaphore
  */
-void fastcall init_rwsem(struct rw_semaphore *sem)
+void __init_rwsem(struct rw_semaphore *sem, const char *name,
+		  struct lock_class_key *key)
 {
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+	/*
+	 * Make sure we are not reinitializing a held semaphore:
+	 */
+	debug_check_no_locks_freed((void *)sem, sizeof(*sem));
+	lockdep_init_map(&sem->dep_map, name, key);
+#endif
 	sem->activity = 0;
 	spin_lock_init(&sem->wait_lock);
 	INIT_LIST_HEAD(&sem->wait_list);
@@ -183,7 +191,7 @@ int fastcall __down_read_trylock(struct rw_semaphore *sem)
  * get a write lock on the semaphore
  * - we increment the waiting count anyway to indicate an exclusive lock
  */
-void fastcall __sched __down_write(struct rw_semaphore *sem)
+void fastcall __sched __down_write_nested(struct rw_semaphore *sem, int subclass)
 {
 	struct rwsem_waiter waiter;
 	struct task_struct *tsk;
@@ -223,6 +231,11 @@ void fastcall __sched __down_write(struct rw_semaphore *sem)
 	;
 }
 
+void fastcall __sched __down_write(struct rw_semaphore *sem)
+{
+	__down_write_nested(sem, 0);
+}
+
 /*
  * trylock for writing -- returns 1 if successful, 0 if contention
  */
@@ -292,9 +305,10 @@ void fastcall __downgrade_write(struct rw_semaphore *sem)
 	spin_unlock_irqrestore(&sem->wait_lock, flags);
 }
 
-EXPORT_SYMBOL(init_rwsem);
+EXPORT_SYMBOL(__init_rwsem);
 EXPORT_SYMBOL(__down_read);
 EXPORT_SYMBOL(__down_read_trylock);
+EXPORT_SYMBOL(__down_write_nested);
 EXPORT_SYMBOL(__down_write);
 EXPORT_SYMBOL(__down_write_trylock);
 EXPORT_SYMBOL(__up_read);

lib/rwsem.c

@@ -8,6 +8,26 @@
 #include <linux/init.h>
 #include <linux/module.h>
 
+/*
+ * Initialize an rwsem:
+ */
+void __init_rwsem(struct rw_semaphore *sem, const char *name,
+		  struct lock_class_key *key)
+{
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+	/*
+	 * Make sure we are not reinitializing a held semaphore:
+	 */
+	debug_check_no_locks_freed((void *)sem, sizeof(*sem));
+	lockdep_init_map(&sem->dep_map, name, key);
+#endif
+	sem->count = RWSEM_UNLOCKED_VALUE;
+	spin_lock_init(&sem->wait_lock);
+	INIT_LIST_HEAD(&sem->wait_list);
+}
+
+EXPORT_SYMBOL(__init_rwsem);
+
 struct rwsem_waiter {
 	struct list_head list;
 	struct task_struct *task;