locking, semaphores: Annotate inner lock as raw

There is no reason to have the spin_lock protecting the semaphore
preemptible on -rt. Annotate it as a raw_spinlock.

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.

( On rt this also solves lockdep complaining about the
  rt_mutex.wait_lock being not initialized. )
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

include/linux/semaphore.h

@@ -14,14 +14,14 @@
 
 /* Please don't access any members of this structure directly */
 struct semaphore {
-	spinlock_t		lock;
+	raw_spinlock_t		lock;
 	unsigned int		count;
 	struct list_head	wait_list;
 };
 
 #define __SEMAPHORE_INITIALIZER(name, n)				\
 {									\
-	.lock		= __SPIN_LOCK_UNLOCKED((name).lock),		\
+	.lock		= __RAW_SPIN_LOCK_UNLOCKED((name).lock),	\
 	.count		= n,						\
 	.wait_list	= LIST_HEAD_INIT((name).wait_list),		\
 }

kernel/semaphore.c

@@ -54,12 +54,12 @@ void down(struct semaphore *sem)
 {
 	unsigned long flags;
 
-	spin_lock_irqsave(&sem->lock, flags);
+	raw_spin_lock_irqsave(&sem->lock, flags);
 	if (likely(sem->count > 0))
 		sem->count--;
 	else
 		__down(sem);
-	spin_unlock_irqrestore(&sem->lock, flags);
+	raw_spin_unlock_irqrestore(&sem->lock, flags);
 }
 EXPORT_SYMBOL(down);
 
@@ -77,12 +77,12 @@ int down_interruptible(struct semaphore *sem)
 	unsigned long flags;
 	int result = 0;
 
-	spin_lock_irqsave(&sem->lock, flags);
+	raw_spin_lock_irqsave(&sem->lock, flags);
 	if (likely(sem->count > 0))
 		sem->count--;
 	else
 		result = __down_interruptible(sem);
-	spin_unlock_irqrestore(&sem->lock, flags);
+	raw_spin_unlock_irqrestore(&sem->lock, flags);
 
 	return result;
 }
@@ -103,12 +103,12 @@ int down_killable(struct semaphore *sem)
 	unsigned long flags;
 	int result = 0;
 
-	spin_lock_irqsave(&sem->lock, flags);
+	raw_spin_lock_irqsave(&sem->lock, flags);
 	if (likely(sem->count > 0))
 		sem->count--;
 	else
 		result = __down_killable(sem);
-	spin_unlock_irqrestore(&sem->lock, flags);
+	raw_spin_unlock_irqrestore(&sem->lock, flags);
 
 	return result;
 }
@@ -132,11 +132,11 @@ int down_trylock(struct semaphore *sem)
 	unsigned long flags;
 	int count;
 
-	spin_lock_irqsave(&sem->lock, flags);
+	raw_spin_lock_irqsave(&sem->lock, flags);
 	count = sem->count - 1;
 	if (likely(count >= 0))
 		sem->count = count;
-	spin_unlock_irqrestore(&sem->lock, flags);
+	raw_spin_unlock_irqrestore(&sem->lock, flags);
 
 	return (count < 0);
 }
@@ -157,12 +157,12 @@ int down_timeout(struct semaphore *sem, long jiffies)
 	unsigned long flags;
 	int result = 0;
 
-	spin_lock_irqsave(&sem->lock, flags);
+	raw_spin_lock_irqsave(&sem->lock, flags);
 	if (likely(sem->count > 0))
 		sem->count--;
 	else
 		result = __down_timeout(sem, jiffies);
-	spin_unlock_irqrestore(&sem->lock, flags);
+	raw_spin_unlock_irqrestore(&sem->lock, flags);
 
 	return result;
 }
@@ -179,12 +179,12 @@ void up(struct semaphore *sem)
 {
 	unsigned long flags;
 
-	spin_lock_irqsave(&sem->lock, flags);
+	raw_spin_lock_irqsave(&sem->lock, flags);
 	if (likely(list_empty(&sem->wait_list)))
 		sem->count++;
 	else
 		__up(sem);
-	spin_unlock_irqrestore(&sem->lock, flags);
+	raw_spin_unlock_irqrestore(&sem->lock, flags);
 }
 EXPORT_SYMBOL(up);
 
@@ -217,9 +217,9 @@ static inline int __sched __down_common(struct semaphore *sem, long state,
 		if (timeout <= 0)
 			goto timed_out;
 		__set_task_state(task, state);
-		spin_unlock_irq(&sem->lock);
+		raw_spin_unlock_irq(&sem->lock);
 		timeout = schedule_timeout(timeout);
-		spin_lock_irq(&sem->lock);
+		raw_spin_lock_irq(&sem->lock);
 		if (waiter.up)
 			return 0;
 	}