134 lines
3.1 KiB
C
134 lines
3.1 KiB
C
/* $Id: semaphore.h,v 1.3 2001/05/08 13:54:09 bjornw Exp $ */
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/* On the i386 these are coded in asm, perhaps we should as well. Later.. */
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#ifndef _CRIS_SEMAPHORE_H
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#define _CRIS_SEMAPHORE_H
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#define RW_LOCK_BIAS 0x01000000
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#include <linux/wait.h>
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#include <linux/spinlock.h>
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#include <linux/rwsem.h>
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#include <asm/system.h>
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#include <asm/atomic.h>
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/*
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* CRIS semaphores, implemented in C-only so far.
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*/
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struct semaphore {
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atomic_t count;
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atomic_t waking;
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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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.waking = ATOMIC_INIT(0), \
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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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static inline void sema_init(struct semaphore *sem, int val)
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{
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*sem = (struct semaphore)__SEMAPHORE_INITIALIZER((*sem),val);
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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 int __down_trylock(struct semaphore * sem);
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extern void __up(struct semaphore * sem);
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/* notice - we probably can do cli/sti here instead of saving */
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static inline void down(struct semaphore * sem)
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{
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unsigned long flags;
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int failed;
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might_sleep();
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/* atomically decrement the semaphores count, and if its negative, we wait */
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cris_atomic_save(sem, flags);
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failed = --(sem->count.counter) < 0;
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cris_atomic_restore(sem, flags);
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if(failed) {
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__down(sem);
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}
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}
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/*
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* This version waits in interruptible state so that the waiting
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* process can be killed. The down_interruptible routine
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* returns negative for signalled and zero for semaphore acquired.
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*/
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static inline int down_interruptible(struct semaphore * sem)
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{
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unsigned long flags;
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int failed;
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might_sleep();
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/* atomically decrement the semaphores count, and if its negative, we wait */
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cris_atomic_save(sem, flags);
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failed = --(sem->count.counter) < 0;
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cris_atomic_restore(sem, flags);
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if(failed)
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failed = __down_interruptible(sem);
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return(failed);
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}
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static inline int down_trylock(struct semaphore * sem)
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{
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unsigned long flags;
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int failed;
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cris_atomic_save(sem, flags);
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failed = --(sem->count.counter) < 0;
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cris_atomic_restore(sem, flags);
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if(failed)
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failed = __down_trylock(sem);
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return(failed);
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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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unsigned long flags;
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int wakeup;
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/* atomically increment the semaphores count, and if it was negative, we wake people */
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cris_atomic_save(sem, flags);
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wakeup = ++(sem->count.counter) <= 0;
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cris_atomic_restore(sem, flags);
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if(wakeup) {
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__up(sem);
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}
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}
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#endif
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