[PATCH] lockdep: prove rwsem locking correctness

Use the lock validator framework to prove rwsem 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>

9 files changed, 184 insertions, 51 deletions

diff --git a/include/asm-i386/rwsem.h b/include/asm-i386/rwsem.h
index 558804e4a039..2f07601562e7 100644
--- a/include/asm-i386/rwsem.h
+++ b/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
  */
diff --git a/include/asm-s390/rwsem.h b/include/asm-s390/rwsem.h
index 0422a085dd56..13ec16965150 100644
--- a/include/asm-s390/rwsem.h
+++ b/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
  */
diff --git a/include/asm-s390/semaphore.h b/include/asm-s390/semaphore.h
index 702cf436698c..32cdc69f39f4 100644
--- a/include/asm-s390/semaphore.h
+++ b/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)
diff --git a/include/linux/rwsem-spinlock.h b/include/linux/rwsem-spinlock.h
index d68afcc36ac9..ae1fcadd598e 100644
--- a/include/linux/rwsem-spinlock.h
+++ b/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));
diff --git a/include/linux/rwsem.h b/include/linux/rwsem.h
index 93581534b915..658afb37c3f5 100644
--- a/include/linux/rwsem.h
+++ b/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 */
diff --git a/kernel/Makefile b/kernel/Makefile
index 3dd994eedc5c..df6ef3263699 100644
--- a/kernel/Makefile
+++ b/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/
diff --git a/kernel/rwsem.c b/kernel/rwsem.c
index 790a99bb25aa..291ded556aa0 100644
--- a/kernel/rwsem.c
+++ b/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
+
+
diff --git a/lib/rwsem-spinlock.c b/lib/rwsem-spinlock.c
index 03b6097eb04e..db4fed74b940 100644
--- a/lib/rwsem-spinlock.c
+++ b/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);
diff --git a/lib/rwsem.c b/lib/rwsem.c
index bae597284889..b322421c2969 100644
--- a/lib/rwsem.c
+++ b/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;