linux/include/asm-m32r/semaphore.h

#ifndef _ASM_M32R_SEMAPHORE_H
#define _ASM_M32R_SEMAPHORE_H

#include <linux/linkage.h>

#ifdef __KERNEL__

/*
 * SMP- and interrupt-safe semaphores..
 *
 * Copyright (C) 1996  Linus Torvalds
 * Copyright (C) 2004, 2006  Hirokazu Takata <takata at linux-m32r.org>
 */

#include <linux/config.h>
#include <linux/wait.h>
#include <linux/rwsem.h>
#include <asm/assembler.h>
#include <asm/system.h>
#include <asm/atomic.h>

struct semaphore {
	atomic_t count;
	int sleepers;
	wait_queue_head_t wait;
};

#define __SEMAPHORE_INITIALIZER(name, n)				\
{									\
	.count		= ATOMIC_INIT(n),				\
	.sleepers	= 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);
 *
 * i'd rather use the more flexible initialization above, but sadly
 * GCC 2.7.2.3 emits a bogus warning. EGCS doesnt. Oh well.
 */
	atomic_set(&sem->count, val);
	sem->sleepers = 0;
	init_waitqueue_head(&sem->wait);
}

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);

/*
 * Atomically decrement the semaphore's count.  If it goes negative,
 * block the calling thread in the TASK_UNINTERRUPTIBLE state.
 */
static inline void down(struct semaphore * sem)
{
	might_sleep();
	if (unlikely(atomic_dec_return(&sem->count) < 0))
		__down(sem);
}

/*
 * Interruptible try to acquire a semaphore.  If we obtained
 * it, return zero.  If we were interrupted, returns -EINTR
 */
static inline int down_interruptible(struct semaphore * sem)
{
	int result = 0;

	might_sleep();
	if (unlikely(atomic_dec_return(&sem->count) < 0))
		result = __down_interruptible(sem);

	return result;
}

/*
 * Non-blockingly attempt to down() a semaphore.
 * Returns zero if we acquired it
 */
static inline int down_trylock(struct semaphore * sem)
{
	unsigned long flags;
	long count;
	int result = 0;

	local_irq_save(flags);
	__asm__ __volatile__ (
		"# down_trylock			\n\t"
		DCACHE_CLEAR("%0", "r4", "%1")
		M32R_LOCK" %0, @%1;		\n\t"
		"addi	%0, #-1;		\n\t"
		M32R_UNLOCK" %0, @%1;		\n\t"
		: "=&r" (count)
		: "r" (&sem->count)
		: "memory"
#ifdef CONFIG_CHIP_M32700_TS1
		, "r4"
#endif	/* CONFIG_CHIP_M32700_TS1 */
	);
	local_irq_restore(flags);

	if (unlikely(count < 0))
		result = __down_trylock(sem);

	return result;
}

/*
 * 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)
{
	if (unlikely(atomic_inc_return(&sem->count) <= 0))
		__up(sem);
}

#endif  /* __KERNEL__ */

#endif  /* _ASM_M32R_SEMAPHORE_H */