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/*
* include/asm-s390/semaphore.h
*
* S390 version
* Copyright (C) 1999,2000 IBM Deutschland Entwicklung GmbH, IBM Corporation
*
* Derived from "include/asm-i386/semaphore.h"
* (C) Copyright 1996 Linus Torvalds
*/
#ifndef _S390_SEMAPHORE_H
#define _S390_SEMAPHORE_H
#include <asm/system.h>
#include <asm/atomic.h>
#include <linux/wait.h>
struct semaphore {
atomic_t count;
int sleepers;
wait_queue_head_t wait;
};
#define __SEM_DEBUG_INIT(name)
#define __SEMAPHORE_INITIALIZER(name,count) \
{ ATOMIC_INIT(count), 0, __WAIT_QUEUE_HEAD_INITIALIZER((name).wait) \
__SEM_DEBUG_INIT(name) }
#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)
{
*sem = (struct semaphore)__SEMAPHORE_INITIALIZER((*sem),val);
}
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_failed(void /* special register calling convention */);
asmlinkage int __down_failed_interruptible(void /* params in registers */);
asmlinkage int __down_failed_trylock(void /* params in registers */);
asmlinkage void __up_wakeup(void /* special register calling convention */);
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 (atomic_dec_return(&sem->count) < 0)
__down(sem);
}
extern inline int down_interruptible(struct semaphore * sem)
{
int ret = 0;
if (atomic_dec_return(&sem->count) < 0)
ret = __down_interruptible(sem);
return ret;
}
extern inline int down_trylock(struct semaphore * sem)
{
int ret = 0;
if (atomic_dec_return(&sem->count) < 0)
ret = __down_trylock(sem);
return ret;
}
extern inline void up(struct semaphore * sem)
{
if (atomic_inc_return(&sem->count) <= 0)
__up(sem);
}
/* rw mutexes (should that be mutices? =) -- throw rw
* spinlocks and semaphores together, and this is what we
* end up with...
*
* The lock is initialized to BIAS. This way, a writer
* subtracts BIAS ands gets 0 for the case of an uncontended
* lock. Readers decrement by 1 and see a positive value
* when uncontended, negative if there are writers waiting
* (in which case it goes to sleep).
*
* The value 0x01000000 supports up to 128 processors and
* lots of processes. BIAS must be chosen such that subl'ing
* BIAS once per CPU will result in the long remaining
* negative.
*
* In terms of fairness, this should result in the lock
* flopping back and forth between readers and writers
* under heavy use.
*
* -ben
*/
struct rw_semaphore {
atomic_t count;
volatile unsigned int write_bias_granted;
volatile unsigned int read_bias_granted;
wait_queue_head_t wait;
wait_queue_head_t write_bias_wait;
};
#define RW_LOCK_BIAS 0x01000000
#define __RWSEM_DEBUG_INIT /* */
#define __RWSEM_INITIALIZER(name,count) \
{ ATOMIC_INIT(count), 0, 0, __WAIT_QUEUE_HEAD_INITIALIZER((name).wait), \
__WAIT_QUEUE_HEAD_INITIALIZER((name).write_bias_wait) \
__SEM_DEBUG_INIT(name) __RWSEM_DEBUG_INIT }
#define __DECLARE_RWSEM_GENERIC(name,count) \
struct rw_semaphore name = __RWSEM_INITIALIZER(name,count)
#define DECLARE_RWSEM(name) __DECLARE_RWSEM_GENERIC(name,RW_LOCK_BIAS)
#define DECLARE_RWSEM_READ_LOCKED(name) __DECLARE_RWSEM_GENERIC(name,RW_LOCK_BIAS-1)
#define DECLARE_RWSEM_WRITE_LOCKED(name) __DECLARE_RWSEM_GENERIC(name,0)
extern inline void init_rwsem(struct rw_semaphore *sem)
{
atomic_set(&sem->count, RW_LOCK_BIAS);
sem->read_bias_granted = 0;
sem->write_bias_granted = 0;
init_waitqueue_head(&sem->wait);
init_waitqueue_head(&sem->write_bias_wait);
}
extern void __down_read_failed(int, struct rw_semaphore *);
extern void __down_write_failed(int, struct rw_semaphore *);
extern void __rwsem_wake(int, struct rw_semaphore *);
extern inline void down_read(struct rw_semaphore *sem)
{
int count;
count = atomic_dec_return(&sem->count);
if (count < 0)
__down_read_failed(count, sem);
}
extern inline void down_write(struct rw_semaphore *sem)
{
int count;
count = atomic_add_return (-RW_LOCK_BIAS, &sem->count);
if (count < 0)
__down_write_failed(count, sem);
}
/* When a reader does a release, the only significant
* case is when there was a writer waiting, and we've
* bumped the count to 0: we must wake the writer up.
*/
extern inline void up_read(struct rw_semaphore *sem)
{
int count;
count = atomic_inc_return(&sem->count);
if (count == 0)
__rwsem_wake(count, sem);
}
/* releasing the writer is easy -- just release it and
* wake up any sleepers.
*/
extern inline void up_write(struct rw_semaphore *sem)
{
int count;
count = atomic_add_return(RW_LOCK_BIAS, &sem->count);
if (count >= 0 && count < RW_LOCK_BIAS)
__rwsem_wake(count, sem);
}
#endif
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