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, 149 deletions

diff --git a/include/asm-alpha/semaphore.h b/include/asm-alpha/semaphore.h
index f1e9278a9fe2..d9b2034ed1d2 100644
--- a/include/asm-alpha/semaphore.h
+++ b/include/asm-alpha/semaphore.h
@@ -1,149 +1 @@
-#ifndef _ALPHA_SEMAPHORE_H
-#define _ALPHA_SEMAPHORE_H
-
-/*
- * SMP- and interrupt-safe semaphores..
- *
- * (C) Copyright 1996 Linus Torvalds
- * (C) Copyright 1996, 2000 Richard Henderson
- */
-
-#include <asm/current.h>
-#include <asm/system.h>
-#include <asm/atomic.h>
-#include <linux/compiler.h>
-#include <linux/wait.h>
-#include <linux/rwsem.h>
-
-struct semaphore {
-	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)
-{
-	/*
-	 * Logically, 
-	 *   *sem = (struct semaphore)__SEMAPHORE_INITIALIZER((*sem),val);
-	 * except that gcc produces better initializing by parts yet.
-	 */
-
-	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 *);
-extern void __down_failed(struct semaphore *);
-extern int  down_interruptible(struct semaphore *);
-extern int  __down_failed_interruptible(struct semaphore *);
-extern int  down_trylock(struct semaphore *);
-extern void up(struct semaphore *);
-extern void __up_wakeup(struct semaphore *);
-
-/*
- * Hidden out of line code is fun, but extremely messy.  Rely on newer
- * compilers to do a respectable job with this.  The contention cases
- * are handled out of line in arch/alpha/kernel/semaphore.c.
- */
-
-static inline void __down(struct semaphore *sem)
-{
-	long count;
-	might_sleep();
-	count = atomic_dec_return(&sem->count);
-	if (unlikely(count < 0))
-		__down_failed(sem);
-}
-
-static inline int __down_interruptible(struct semaphore *sem)
-{
-	long count;
-	might_sleep();
-	count = atomic_dec_return(&sem->count);
-	if (unlikely(count < 0))
-		return __down_failed_interruptible(sem);
-	return 0;
-}
-
-/*
- * down_trylock returns 0 on success, 1 if we failed to get the lock.
- */
-
-static inline int __down_trylock(struct semaphore *sem)
-{
-	long ret;
-
-	/* "Equivalent" C:
-
-	   do {
-		ret = ldl_l;
-		--ret;
-		if (ret < 0)
-			break;
-		ret = stl_c = ret;
-	   } while (ret == 0);
-	*/
-	__asm__ __volatile__(
-		"1:	ldl_l	%0,%1\n"
-		"	subl	%0,1,%0\n"
-		"	blt	%0,2f\n"
-		"	stl_c	%0,%1\n"
-		"	beq	%0,3f\n"
-		"	mb\n"
-		"2:\n"
-		".subsection 2\n"
-		"3:	br	1b\n"
-		".previous"
-		: "=&r" (ret), "=m" (sem->count)
-		: "m" (sem->count));
-
-	return ret < 0;
-}
-
-static inline void __up(struct semaphore *sem)
-{
-	if (unlikely(atomic_inc_return(&sem->count) <= 0))
-		__up_wakeup(sem);
-}
-
-#if !defined(CONFIG_DEBUG_SEMAPHORE)
-extern inline void down(struct semaphore *sem)
-{
-	__down(sem);
-}
-extern inline int down_interruptible(struct semaphore *sem)
-{
-	return __down_interruptible(sem);
-}
-extern inline int down_trylock(struct semaphore *sem)
-{
-	return __down_trylock(sem);
-}
-extern inline void up(struct semaphore *sem)
-{
-	__up(sem);
-}
-#endif
-
-#endif
+#include <linux/semaphore.h>