110 строки
2.6 KiB
C
110 строки
2.6 KiB
C
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/*
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* This file is subject to the terms and conditions of the GNU General Public
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* License. See the file "COPYING" in the main directory of this archive
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* for more details.
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*
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* Copyright (C) 1996 Linus Torvalds
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* Copyright (C) 1998, 99, 2000, 01, 04 Ralf Baechle
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* Copyright (C) 1999, 2000, 01 Silicon Graphics, Inc.
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* Copyright (C) 2000, 01 MIPS Technologies, Inc.
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*
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* In all honesty, little of the old MIPS code left - the PPC64 variant was
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* just looking nice and portable so I ripped it. Credits to whoever wrote
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* it.
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*/
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#ifndef __ASM_SEMAPHORE_H
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#define __ASM_SEMAPHORE_H
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/*
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* Remove spinlock-based RW semaphores; RW semaphore definitions are
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* now in rwsem.h and we use the generic lib/rwsem.c implementation.
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* Rework semaphores to use atomic_dec_if_positive.
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* -- Paul Mackerras (paulus@samba.org)
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*/
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#ifdef __KERNEL__
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#include <asm/atomic.h>
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#include <asm/system.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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/*
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* Note that any negative value of count is equivalent to 0,
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* but additionally indicates that some process(es) might be
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* sleeping on `wait'.
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*/
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atomic_t count;
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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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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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extern void __down(struct semaphore * sem);
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extern int __down_interruptible(struct semaphore * sem);
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extern void __up(struct semaphore * sem);
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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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/*
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* Try to get the semaphore, take the slow path if we fail.
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*/
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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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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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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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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 /* __KERNEL__ */
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#endif /* __ASM_SEMAPHORE_H */
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