locking, rwsem: Annotate inner lock as raw

There is no reason to allow the lock protecting rwsems (the
ownerless variant) to be preemptible on -rt. Convert it to raw.

In mainline this change documents the low level nature of
the lock - otherwise there's no functional difference. Lockdep
and Sparse checking will work as usual.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

include/linux/rwsem-spinlock.h

@@ -22,7 +22,7 @@
  */
 struct rw_semaphore {
 	__s32			activity;
-	spinlock_t		wait_lock;
+	raw_spinlock_t		wait_lock;
 	struct list_head	wait_list;
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 	struct lockdep_map dep_map;

include/linux/rwsem.h

@@ -25,7 +25,7 @@ struct rw_semaphore;
 /* All arch specific implementations share the same struct */
 struct rw_semaphore {
 	long			count;
-	spinlock_t		wait_lock;
+	raw_spinlock_t		wait_lock;
 	struct list_head	wait_list;
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 	struct lockdep_map	dep_map;
@@ -56,9 +56,11 @@ static inline int rwsem_is_locked(struct rw_semaphore *sem)
 # define __RWSEM_DEP_MAP_INIT(lockname)
 #endif
 
-#define __RWSEM_INITIALIZER(name) \
-	{ RWSEM_UNLOCKED_VALUE, __SPIN_LOCK_UNLOCKED(name.wait_lock),	\
-	  LIST_HEAD_INIT((name).wait_list) __RWSEM_DEP_MAP_INIT(name) }
+#define __RWSEM_INITIALIZER(name)			\
+	{ RWSEM_UNLOCKED_VALUE,				\
+	  __RAW_SPIN_LOCK_UNLOCKED(name.wait_lock),	\
+	  LIST_HEAD_INIT((name).wait_list)		\
+	  __RWSEM_DEP_MAP_INIT(name) }
 
 #define DECLARE_RWSEM(name) \
 	struct rw_semaphore name = __RWSEM_INITIALIZER(name)

lib/rwsem-spinlock.c

@@ -22,9 +22,9 @@ int rwsem_is_locked(struct rw_semaphore *sem)
 	int ret = 1;
 	unsigned long flags;
 
-	if (spin_trylock_irqsave(&sem->wait_lock, flags)) {
+	if (raw_spin_trylock_irqsave(&sem->wait_lock, flags)) {
 		ret = (sem->activity != 0);
-		spin_unlock_irqrestore(&sem->wait_lock, flags);
+		raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
 	}
 	return ret;
 }
@@ -44,7 +44,7 @@ void __init_rwsem(struct rw_semaphore *sem, const char *name,
 	lockdep_init_map(&sem->dep_map, name, key, 0);
 #endif
 	sem->activity = 0;
-	spin_lock_init(&sem->wait_lock);
+	raw_spin_lock_init(&sem->wait_lock);
 	INIT_LIST_HEAD(&sem->wait_list);
 }
 EXPORT_SYMBOL(__init_rwsem);
@@ -145,12 +145,12 @@ void __sched __down_read(struct rw_semaphore *sem)
 	struct task_struct *tsk;
 	unsigned long flags;
 
-	spin_lock_irqsave(&sem->wait_lock, flags);
+	raw_spin_lock_irqsave(&sem->wait_lock, flags);
 
 	if (sem->activity >= 0 && list_empty(&sem->wait_list)) {
 		/* granted */
 		sem->activity++;
-		spin_unlock_irqrestore(&sem->wait_lock, flags);
+		raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
 		goto out;
 	}
 
@@ -165,7 +165,7 @@ void __sched __down_read(struct rw_semaphore *sem)
 	list_add_tail(&waiter.list, &sem->wait_list);
 
 	/* we don't need to touch the semaphore struct anymore */
-	spin_unlock_irqrestore(&sem->wait_lock, flags);
+	raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
 
 	/* wait to be given the lock */
 	for (;;) {
@@ -189,7 +189,7 @@ int __down_read_trylock(struct rw_semaphore *sem)
 	int ret = 0;
 
 
-	spin_lock_irqsave(&sem->wait_lock, flags);
+	raw_spin_lock_irqsave(&sem->wait_lock, flags);
 
 	if (sem->activity >= 0 && list_empty(&sem->wait_list)) {
 		/* granted */
@@ -197,7 +197,7 @@ int __down_read_trylock(struct rw_semaphore *sem)
 		ret = 1;
 	}
 
-	spin_unlock_irqrestore(&sem->wait_lock, flags);
+	raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
 
 	return ret;
 }
@@ -212,12 +212,12 @@ void __sched __down_write_nested(struct rw_semaphore *sem, int subclass)
 	struct task_struct *tsk;
 	unsigned long flags;
 
-	spin_lock_irqsave(&sem->wait_lock, flags);
+	raw_spin_lock_irqsave(&sem->wait_lock, flags);
 
 	if (sem->activity == 0 && list_empty(&sem->wait_list)) {
 		/* granted */
 		sem->activity = -1;
-		spin_unlock_irqrestore(&sem->wait_lock, flags);
+		raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
 		goto out;
 	}
 
@@ -232,7 +232,7 @@ void __sched __down_write_nested(struct rw_semaphore *sem, int subclass)
 	list_add_tail(&waiter.list, &sem->wait_list);
 
 	/* we don't need to touch the semaphore struct anymore */
-	spin_unlock_irqrestore(&sem->wait_lock, flags);
+	raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
 
 	/* wait to be given the lock */
 	for (;;) {
@@ -260,7 +260,7 @@ int __down_write_trylock(struct rw_semaphore *sem)
 	unsigned long flags;
 	int ret = 0;
 
-	spin_lock_irqsave(&sem->wait_lock, flags);
+	raw_spin_lock_irqsave(&sem->wait_lock, flags);
 
 	if (sem->activity == 0 && list_empty(&sem->wait_list)) {
 		/* granted */
@@ -268,7 +268,7 @@ int __down_write_trylock(struct rw_semaphore *sem)
 		ret = 1;
 	}
 
-	spin_unlock_irqrestore(&sem->wait_lock, flags);
+	raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
 
 	return ret;
 }
@@ -280,12 +280,12 @@ void __up_read(struct rw_semaphore *sem)
 {
 	unsigned long flags;
 
-	spin_lock_irqsave(&sem->wait_lock, flags);
+	raw_spin_lock_irqsave(&sem->wait_lock, flags);
 
 	if (--sem->activity == 0 && !list_empty(&sem->wait_list))
 		sem = __rwsem_wake_one_writer(sem);
 
-	spin_unlock_irqrestore(&sem->wait_lock, flags);
+	raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
 }
 
 /*
@@ -295,13 +295,13 @@ void __up_write(struct rw_semaphore *sem)
 {
 	unsigned long flags;
 
-	spin_lock_irqsave(&sem->wait_lock, flags);
+	raw_spin_lock_irqsave(&sem->wait_lock, flags);
 
 	sem->activity = 0;
 	if (!list_empty(&sem->wait_list))
 		sem = __rwsem_do_wake(sem, 1);
 
-	spin_unlock_irqrestore(&sem->wait_lock, flags);
+	raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
 }
 
 /*
@@ -312,12 +312,12 @@ void __downgrade_write(struct rw_semaphore *sem)
 {
 	unsigned long flags;
 
-	spin_lock_irqsave(&sem->wait_lock, flags);
+	raw_spin_lock_irqsave(&sem->wait_lock, flags);
 
 	sem->activity = 1;
 	if (!list_empty(&sem->wait_list))
 		sem = __rwsem_do_wake(sem, 0);
 
-	spin_unlock_irqrestore(&sem->wait_lock, flags);
+	raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
 }
 

lib/rwsem.c

@@ -22,7 +22,7 @@ void __init_rwsem(struct rw_semaphore *sem, const char *name,
 	lockdep_init_map(&sem->dep_map, name, key, 0);
 #endif
 	sem->count = RWSEM_UNLOCKED_VALUE;
-	spin_lock_init(&sem->wait_lock);
+	raw_spin_lock_init(&sem->wait_lock);
 	INIT_LIST_HEAD(&sem->wait_list);
 }
 
@@ -180,7 +180,7 @@ rwsem_down_failed_common(struct rw_semaphore *sem,
 	set_task_state(tsk, TASK_UNINTERRUPTIBLE);
 
 	/* set up my own style of waitqueue */
-	spin_lock_irq(&sem->wait_lock);
+	raw_spin_lock_irq(&sem->wait_lock);
 	waiter.task = tsk;
 	waiter.flags = flags;
 	get_task_struct(tsk);
@@ -204,7 +204,7 @@ rwsem_down_failed_common(struct rw_semaphore *sem,
 		 adjustment == -RWSEM_ACTIVE_WRITE_BIAS)
 		sem = __rwsem_do_wake(sem, RWSEM_WAKE_READ_OWNED);
 
-	spin_unlock_irq(&sem->wait_lock);
+	raw_spin_unlock_irq(&sem->wait_lock);
 
 	/* wait to be given the lock */
 	for (;;) {
@@ -245,13 +245,13 @@ struct rw_semaphore *rwsem_wake(struct rw_semaphore *sem)
 {
 	unsigned long flags;
 
-	spin_lock_irqsave(&sem->wait_lock, flags);
+	raw_spin_lock_irqsave(&sem->wait_lock, flags);
 
 	/* do nothing if list empty */
 	if (!list_empty(&sem->wait_list))
 		sem = __rwsem_do_wake(sem, RWSEM_WAKE_ANY);
 
-	spin_unlock_irqrestore(&sem->wait_lock, flags);
+	raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
 
 	return sem;
 }
@@ -265,13 +265,13 @@ struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem)
 {
 	unsigned long flags;
 
-	spin_lock_irqsave(&sem->wait_lock, flags);
+	raw_spin_lock_irqsave(&sem->wait_lock, flags);
 
 	/* do nothing if list empty */
 	if (!list_empty(&sem->wait_list))
 		sem = __rwsem_do_wake(sem, RWSEM_WAKE_READ_OWNED);
 
-	spin_unlock_irqrestore(&sem->wait_lock, flags);
+	raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
 
 	return sem;
 }