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/*
* SMP- and interrupt-safe semaphores..
*
* 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.
*
* (C) Copyright 1996 Linus Torvalds
* (C) Copyright 1998, 99, 2000, 01 Ralf Baechle
* (C) Copyright 1999, 2000 Silicon Graphics, Inc.
* Copyright (C) 2000, 01 MIPS Technologies, Inc. All rights reserved.
*/
#ifndef _ASM_SEMAPHORE_H
#define _ASM_SEMAPHORE_H
#include <asm/system.h>
#include <asm/atomic.h>
#include <linux/spinlock.h>
#include <linux/wait.h>
#include <linux/config.h>
#include <linux/rwsem.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
} __attribute__((aligned(8)));
#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)
static 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);
static inline void down(struct semaphore * sem)
{
#if WAITQUEUE_DEBUG
CHECK_MAGIC(sem->__magic);
#endif
if (atomic_dec_return(&sem->count) < 0)
__down(sem);
}
/*
* Interruptible try to acquire a semaphore. If we obtained
* it, return zero. If we were interrupted, returns -EINTR
*/
static 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;
}
#ifndef CONFIG_CPU_HAS_LLDSCD
/*
* Non-blockingly attempt to down() a semaphore.
* Returns zero if we acquired it
*/
static inline int down_trylock(struct semaphore * sem)
{
int ret = 0;
if (atomic_dec_return(&sem->count) < 0)
ret = __down_trylock(sem);
return ret;
}
#else
/*
* 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 do this by using lld/scd on the pair of 32-bit words. This
* won't work on MIPS32 platforms, however, and must be rewritten.
*
* 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)
* }
* }
*/
static inline int down_trylock(struct semaphore * sem)
{
long ret, tmp, tmp2, sub;
#if WAITQUEUE_DEBUG
CHECK_MAGIC(sem->__magic);
#endif
__asm__ __volatile__(
".set\tmips3\t\t\t# down_trylock\n"
"0:\tlld\t%1, %4\n\t"
"dli\t%3, 0x0000000100000000\n\t"
"dsubu\t%1, %3\n\t"
"li\t%0, 0\n\t"
"bgez\t%1, 2f\n\t"
"sll\t%2, %1, 0\n\t"
"blez\t%2, 1f\n\t"
"daddiu\t%1, %1, -1\n\t"
"b\t2f\n\t"
"1:\tdaddu\t%1, %1, %3\n"
"li\t%0, 1\n"
"2:\tscd\t%1, %4\n\t"
"beqz\t%1, 0b\n\t"
".set mips0"
: "=&r"(ret), "=&r"(tmp), "=&r"(tmp2), "=&r"(sub)
: "m"(*sem)
: "memory");
return ret;
}
#endif /* CONFIG_CPU_HAS_LLDSCD */
/*
* Note! This is subtle. We jump to wake people up only if
* the semaphore was negative (== somebody was waiting on it).
*/
static inline void up(struct semaphore * sem)
{
#if WAITQUEUE_DEBUG
CHECK_MAGIC(sem->__magic);
#endif
if (atomic_inc_return(&sem->count) <= 0)
__up(sem);
}
static inline int sem_getcount(struct semaphore *sem)
{
return atomic_read(&sem->count);
}
#endif /* _ASM_SEMAPHORE_H */
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