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/* $Id: semaphore.h,v 1.3 2001/05/08 13:54:09 bjornw Exp $ */
/* On the i386 these are coded in asm, perhaps we should as well. Later.. */
#ifndef _CRIS_SEMAPHORE_H
#define _CRIS_SEMAPHORE_H
#define RW_LOCK_BIAS 0x01000000
#include <linux/wait.h>
#include <linux/spinlock.h>
#include <linux/rwsem.h>
#include <asm/system.h>
#include <asm/atomic.h>
/*
* CRIS semaphores, implemented in C-only so far.
*/
struct semaphore {
atomic_t count;
atomic_t waking;
wait_queue_head_t wait;
};
#define __SEMAPHORE_INITIALIZER(name, n) \
{ \
.count = ATOMIC_INIT(n), \
.waking = ATOMIC_INIT(0), \
.wait = __WAIT_QUEUE_HEAD_INITIALIZER((name).wait) \
}
#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)
{
*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);
}
extern void __down(struct semaphore * sem);
extern int __down_interruptible(struct semaphore * sem);
extern int __down_trylock(struct semaphore * sem);
extern void __up(struct semaphore * sem);
/* notice - we probably can do cli/sti here instead of saving */
static inline void down(struct semaphore * sem)
{
unsigned long flags;
int failed;
might_sleep();
/* atomically decrement the semaphores count, and if its negative, we wait */
cris_atomic_save(sem, flags);
failed = --(sem->count.counter) < 0;
cris_atomic_restore(sem, flags);
if(failed) {
__down(sem);
}
}
/*
* This version waits in interruptible state so that the waiting
* process can be killed. The down_interruptible routine
* returns negative for signalled and zero for semaphore acquired.
*/
static inline int down_interruptible(struct semaphore * sem)
{
unsigned long flags;
int failed;
might_sleep();
/* atomically decrement the semaphores count, and if its negative, we wait */
cris_atomic_save(sem, flags);
failed = --(sem->count.counter) < 0;
cris_atomic_restore(sem, flags);
if(failed)
failed = __down_interruptible(sem);
return(failed);
}
static inline int down_trylock(struct semaphore * sem)
{
unsigned long flags;
int failed;
cris_atomic_save(sem, flags);
failed = --(sem->count.counter) < 0;
cris_atomic_restore(sem, flags);
if(failed)
failed = __down_trylock(sem);
return(failed);
}
/*
* Note! This is subtle. We jump to wake people up only if
* the semaphore was negative (== somebody was waiting on it).
* The default case (no contention) will result in NO
* jumps for both down() and up().
*/
static inline void up(struct semaphore * sem)
{
unsigned long flags;
int wakeup;
/* atomically increment the semaphores count, and if it was negative, we wake people */
cris_atomic_save(sem, flags);
wakeup = ++(sem->count.counter) <= 0;
cris_atomic_restore(sem, flags);
if(wakeup) {
__up(sem);
}
}
#endif
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