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/* $Id: semaphore.h,v 1.3 1999/12/04 03:59:12 ralf Exp $
*
* License. See the file "COPYING" in the main directory of this archive
* for more details.
*
* Copyright (C) 1996 Linus Torvalds
* Copyright (C) 1998, 1999 Ralf Baechle
* Copyright (C) 1999 Silicon Graphics, Inc.
*/
#ifndef _ASM_SEMAPHORE_H
#define _ASM_SEMAPHORE_H
#include <asm/system.h>
#include <asm/atomic.h>
#include <linux/spinlock.h>
#include <linux/wait.h>
struct semaphore {
#ifdef __MIPSEB__
atomic_t count;
atomic_t waking;
#else
atomic_t waking;
atomic_t count;
#endif
wait_queue_head_t wait;
#if WAITQUEUE_DEBUG
long __magic;
#endif
};
#if WAITQUEUE_DEBUG
# define __SEM_DEBUG_INIT(name) \
, (long)&(name).__magic
#else
# define __SEM_DEBUG_INIT(name)
#endif
#ifdef __MIPSEB__
#define __SEMAPHORE_INITIALIZER(name,count) \
{ ATOMIC_INIT(count), ATOMIC_INIT(0), __WAIT_QUEUE_HEAD_INITIALIZER((name).wait) \
__SEM_DEBUG_INIT(name) }
#else
#define __SEMAPHORE_INITIALIZER(name,count) \
{ ATOMIC_INIT(0), ATOMIC_INIT(count), __WAIT_QUEUE_HEAD_INITIALIZER((name).wait) \
__SEM_DEBUG_INIT(name) }
#endif
#define __MUTEX_INITIALIZER(name) \
__SEMAPHORE_INITIALIZER(name,1)
#define __DECLARE_SEMAPHORE_GENERIC(name,count) \
struct semaphore name = __SEMAPHORE_INITIALIZER(name,count)
#define DECLARE_MUTEX(name) __DECLARE_SEMAPHORE_GENERIC(name,1)
#define DECLARE_MUTEX_LOCKED(name) __DECLARE_SEMAPHORE_GENERIC(name,0)
extern inline void sema_init (struct semaphore *sem, int val)
{
atomic_set(&sem->count, val);
atomic_set(&sem->waking, 0);
init_waitqueue_head(&sem->wait);
#if WAITQUEUE_DEBUG
sem->__magic = (long)&sem->__magic;
#endif
}
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);
}
asmlinkage void __down(struct semaphore * sem);
asmlinkage int __down_interruptible(struct semaphore * sem);
asmlinkage int __down_trylock(struct semaphore * sem);
asmlinkage void __up(struct semaphore * sem);
extern inline void down(struct semaphore * sem)
{
#if WAITQUEUE_DEBUG
CHECK_MAGIC(sem->__magic);
#endif
if (atomic_dec_return(&sem->count) < 0)
__down(sem);
}
extern inline int down_interruptible(struct semaphore * sem)
{
int ret = 0;
#if WAITQUEUE_DEBUG
CHECK_MAGIC(sem->__magic);
#endif
if (atomic_dec_return(&sem->count) < 0)
ret = __down_interruptible(sem);
return ret;
}
/*
* down_trylock returns 0 on success, 1 if we failed to get the lock.
*
* We must manipulate count and waking simultaneously and atomically.
* Here, we this by using ll/sc on the pair of 32-bit words.
*
* Pseudocode:
*
* Decrement(sem->count)
* If(sem->count >=0) {
* Return(SUCCESS) // resource is free
* } else {
* If(sem->waking <= 0) { // if no wakeup pending
* Increment(sem->count) // undo decrement
* Return(FAILURE)
* } else {
* Decrement(sem->waking) // otherwise "steal" wakeup
* Return(SUCCESS)
* }
* }
*/
extern inline int down_trylock(struct semaphore * sem)
{
long ret, tmp, tmp2, sub;
#if WAITQUEUE_DEBUG
CHECK_MAGIC(sem->__magic);
#endif
__asm__ __volatile__("
.set mips3
0: lld %1, %4
dli %3, 0x0000000100000000
dsubu %1, %3
li %0, 0
bgez %1, 2f
sll %2, %1, 0
blez %2, 1f
daddiu %1, %1, -1
b 2f
1:
daddu %1, %1, %3
li %0, 1
2:
scd %1, %4
beqz %1, 0b
.set mips0"
: "=&r"(ret), "=&r"(tmp), "=&r"(tmp2), "=&r"(sub)
: "m"(*sem)
: "memory");
return ret;
}
/*
* Note! This is subtle. We jump to wake people up only if
* the semaphore was negative (== somebody was waiting on it).
*/
extern inline void up(struct semaphore * sem)
{
#if WAITQUEUE_DEBUG
CHECK_MAGIC(sem->__magic);
#endif
if (atomic_inc_return(&sem->count) <= 0)
__up(sem);
}
#endif /* _ASM_SEMAPHORE_H */
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