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, 108 deletions

diff --git a/include/asm-mips/semaphore.h b/include/asm-mips/semaphore.h
index fdf8042b784b..d9b2034ed1d2 100644
--- a/include/asm-mips/semaphore.h
+++ b/include/asm-mips/semaphore.h
@@ -1,108 +1 @@
-/*
- * This file is subject to the terms and conditions of the GNU General Public
- * License.  See the file "COPYING" in the main directory of this archive
- * for more details.
- *
- * Copyright (C) 1996  Linus Torvalds
- * Copyright (C) 1998, 99, 2000, 01, 04  Ralf Baechle
- * Copyright (C) 1999, 2000, 01  Silicon Graphics, Inc.
- * Copyright (C) 2000, 01 MIPS Technologies, Inc.
- *
- * In all honesty, little of the old MIPS code left - the PPC64 variant was
- * just looking nice and portable so I ripped it.  Credits to whoever wrote
- * it.
- */
-#ifndef __ASM_SEMAPHORE_H
-#define __ASM_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_SEMAPHORE_H */
+#include <linux/semaphore.h>