Generic semaphore implementation

Semaphores are no longer performance-critical, so a generic C
implementation is better for maintainability, debuggability and
extensibility.  Thanks to Peter Zijlstra for fixing the lockdep
warning.  Thanks to Harvey Harrison for pointing out that the
unlikely() was unnecessary.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Acked-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 1 insertions, 94 deletions

diff --git a/include/asm-powerpc/semaphore.h b/include/asm-powerpc/semaphore.h
index 48dd32e07749..d9b2034ed1d2 100644
--- a/include/asm-powerpc/semaphore.h
+++ b/include/asm-powerpc/semaphore.h
@@ -1,94 +1 @@
-#ifndef _ASM_POWERPC_SEMAPHORE_H
-#define _ASM_POWERPC_SEMAPHORE_H
-
-/*
- * Remove spinlock-based RW semaphores; RW semaphore definitions are
- * now in rwsem.h and we use the generic lib/rwsem.c implementation.
- * Rework semaphores to use atomic_dec_if_positive.
- * -- Paul Mackerras (paulus@samba.org)
- */
-
-#ifdef __KERNEL__
-
-#include <asm/atomic.h>
-#include <asm/system.h>
-#include <linux/wait.h>
-#include <linux/rwsem.h>
-
-struct semaphore {
-	/*
-	 * Note that any negative value of count is equivalent to 0,
-	 * but additionally indicates that some process(es) might be
-	 * sleeping on `wait'.
-	 */
-	atomic_t count;
-	wait_queue_head_t wait;
-};
-
-#define __SEMAPHORE_INITIALIZER(name, n)				\
-{									\
-	.count		= ATOMIC_INIT(n),				\
-	.wait		= __WAIT_QUEUE_HEAD_INITIALIZER((name).wait)	\
-}
-
-#define __DECLARE_SEMAPHORE_GENERIC(name, count) \
-	struct semaphore name = __SEMAPHORE_INITIALIZER(name,count)
-
-#define DECLARE_MUTEX(name)		__DECLARE_SEMAPHORE_GENERIC(name, 1)
-
-static inline void sema_init (struct semaphore *sem, int val)
-{
-	atomic_set(&sem->count, val);
-	init_waitqueue_head(&sem->wait);
-}
-
-static inline void init_MUTEX (struct semaphore *sem)
-{
-	sema_init(sem, 1);
-}
-
-static inline void init_MUTEX_LOCKED (struct semaphore *sem)
-{
-	sema_init(sem, 0);
-}
-
-extern void __down(struct semaphore * sem);
-extern int  __down_interruptible(struct semaphore * sem);
-extern void __up(struct semaphore * sem);
-
-static inline void down(struct semaphore * sem)
-{
-	might_sleep();
-
-	/*
-	 * Try to get the semaphore, take the slow path if we fail.
-	 */
-	if (unlikely(atomic_dec_return(&sem->count) < 0))
-		__down(sem);
-}
-
-static inline int down_interruptible(struct semaphore * sem)
-{
-	int ret = 0;
-
-	might_sleep();
-
-	if (unlikely(atomic_dec_return(&sem->count) < 0))
-		ret = __down_interruptible(sem);
-	return ret;
-}
-
-static inline int down_trylock(struct semaphore * sem)
-{
-	return atomic_dec_if_positive(&sem->count) < 0;
-}
-
-static inline void up(struct semaphore * sem)
-{
-	if (unlikely(atomic_inc_return(&sem->count) <= 0))
-		__up(sem);
-}
-
-#endif /* __KERNEL__ */
-
-#endif /* _ASM_POWERPC_SEMAPHORE_H */
+#include <linux/semaphore.h>