110 lines
2.6 KiB
C
110 lines
2.6 KiB
C
/*
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* SMP- and interrupt-safe semaphores.
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*
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* Copyright (C) 2006 Atmel Corporation
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*
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* Based on include/asm-i386/semaphore.h
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* Copyright (C) 1996 Linus Torvalds
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#ifndef __ASM_AVR32_SEMAPHORE_H
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#define __ASM_AVR32_SEMAPHORE_H
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#include <linux/linkage.h>
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#include <asm/system.h>
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#include <asm/atomic.h>
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#include <linux/wait.h>
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#include <linux/rwsem.h>
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struct semaphore {
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atomic_t count;
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int sleepers;
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wait_queue_head_t wait;
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};
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#define __SEMAPHORE_INITIALIZER(name, n) \
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{ \
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.count = ATOMIC_INIT(n), \
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.wait = __WAIT_QUEUE_HEAD_INITIALIZER((name).wait) \
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}
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#define __DECLARE_SEMAPHORE_GENERIC(name,count) \
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struct semaphore name = __SEMAPHORE_INITIALIZER(name,count)
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#define DECLARE_MUTEX(name) __DECLARE_SEMAPHORE_GENERIC(name,1)
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#define DECLARE_MUTEX_LOCKED(name) __DECLARE_SEMAPHORE_GENERIC(name,0)
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static inline void sema_init (struct semaphore *sem, int val)
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{
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atomic_set(&sem->count, val);
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sem->sleepers = 0;
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init_waitqueue_head(&sem->wait);
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}
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static inline void init_MUTEX (struct semaphore *sem)
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{
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sema_init(sem, 1);
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}
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static inline void init_MUTEX_LOCKED (struct semaphore *sem)
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{
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sema_init(sem, 0);
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}
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void __down(struct semaphore * sem);
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int __down_interruptible(struct semaphore * sem);
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void __up(struct semaphore * sem);
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/*
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* This is ugly, but we want the default case to fall through.
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* "__down_failed" is a special asm handler that calls the C
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* routine that actually waits. See arch/i386/kernel/semaphore.c
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*/
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static inline void down(struct semaphore * sem)
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{
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might_sleep();
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if (unlikely(atomic_dec_return (&sem->count) < 0))
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__down (sem);
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}
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/*
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* Interruptible try to acquire a semaphore. If we obtained
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* it, return zero. If we were interrupted, returns -EINTR
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*/
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static inline int down_interruptible(struct semaphore * sem)
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{
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int ret = 0;
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might_sleep();
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if (unlikely(atomic_dec_return (&sem->count) < 0))
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ret = __down_interruptible (sem);
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return ret;
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}
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/*
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* Non-blockingly attempt to down() a semaphore.
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* Returns zero if we acquired it
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*/
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static inline int down_trylock(struct semaphore * sem)
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{
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return atomic_dec_if_positive(&sem->count) < 0;
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}
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/*
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* Note! This is subtle. We jump to wake people up only if
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* the semaphore was negative (== somebody was waiting on it).
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* The default case (no contention) will result in NO
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* jumps for both down() and up().
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*/
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static inline void up(struct semaphore * sem)
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{
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if (unlikely(atomic_inc_return (&sem->count) <= 0))
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__up (sem);
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}
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#endif /*__ASM_AVR32_SEMAPHORE_H */
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