semaphore.h

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/*
 * linux/include/asm-arm/semaphore.h
 */
#ifndef __ASM_ARM_SEMAPHORE_H
#define __ASM_ARM_SEMAPHORE_H

#include <linux/linkage.h>
#include <linux/spinlock.h>
#include <linux/wait.h>

#include <asm/atomic.h>
#include <asm/proc/locks.h>

struct semaphore {
	atomic_t count;
	int sleepers;
	wait_queue_head_t wait;
#if WAITQUEUE_DEBUG
	long __magic;
#endif
};

#if WAITQUEUE_DEBUG
# define __SEM_DEBUG_INIT(name) \
		, (long)&(name).__magic
#else
# define __SEM_DEBUG_INIT(name)
#endif

#define __SEMAPHORE_INIT(name,count)			\
	{ ATOMIC_INIT(count), 0,			\
	  __WAIT_QUEUE_HEAD_INITIALIZER((name).wait)	\
	  __SEM_DEBUG_INIT(name) }

#define __MUTEX_INITIALIZER(name) \
	__SEMAPHORE_INIT(name,1)

#define __DECLARE_SEMAPHORE_GENERIC(name,count)	\
	struct semaphore name = __SEMAPHORE_INIT(name,count)

#define DECLARE_MUTEX(name)		__DECLARE_SEMAPHORE_GENERIC(name,1)
#define DECLARE_MUTEX_LOCKED(name)	__DECLARE_SEMAPHORE_GENERIC(name,0)

extern inline void sema_init(struct semaphore *sem, int val)
{
	atomic_set(&sem->count, val);
	sem->sleepers = 0;
	init_waitqueue_head(&sem->wait);
#if WAITQUEUE_DEBUG
	sem->__magic = (long)&sem->__magic;
#endif
}

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);
}

/*
 * special register calling convention
 */
asmlinkage void __down_failed(void);
asmlinkage int  __down_interruptible_failed(void);
asmlinkage int  __down_trylock_failed(void);
asmlinkage void __up_wakeup(void);

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);

/*
 * This is ugly, but we want the default case to fall through.
 * "__down" is the actual routine that waits...
 */
extern inline void down(struct semaphore * sem)
{
#if WAITQUEUE_DEBUG
	CHECK_MAGIC(sem->__magic);
#endif

	__down_op(sem, __down_failed);
}

/*
 * This is ugly, but we want the default case to fall through.
 * "__down_interruptible" is the actual routine that waits...
 */
extern inline int down_interruptible (struct semaphore * sem)
{
#if WAITQUEUE_DEBUG
	CHECK_MAGIC(sem->__magic);
#endif

	return __down_op_ret(sem, __down_interruptible_failed);
}

extern inline int down_trylock(struct semaphore *sem)
{
#if WAITQUEUE_DEBUG
	CHECK_MAGIC(sem->__magic);
#endif

	return __down_op_ret(sem, __down_trylock_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().
 */
extern inline void up(struct semaphore * sem)
{
#if WAITQUEUE_DEBUG
	CHECK_MAGIC(sem->__magic);
#endif

	__up_op(sem, __up_wakeup);
}

/* rw mutexes (should that be mutices? =) -- throw rw
 * spinlocks and semaphores together, and this is what we
 * end up with...
 *
 * The lock is initialized to BIAS.  This way, a writer
 * subtracts BIAS ands gets 0 for the case of an uncontended
 * lock.  Readers decrement by 1 and see a positive value
 * when uncontended, negative if there are writers waiting
 * (in which case it goes to sleep).
 *
 * In terms of fairness, this should result in the lock
 * flopping back and forth between readers and writers
 * under heavy use.
 *
 *              -ben
 */
struct rw_semaphore {
	atomic_t                count;
	volatile unsigned char  write_bias_granted;
	volatile unsigned char  read_bias_granted;
	volatile unsigned char  pad1;
	volatile unsigned char  pad2;
	wait_queue_head_t       wait;
	wait_queue_head_t	write_bias_wait;
#if WAITQUEUE_DEBUG
	long			__magic;
	atomic_t		readers;
	atomic_t		writers;
#endif
};

#if WAITQUEUE_DEBUG
#define __RWSEM_DEBUG_INIT	, ATOMIC_INIT(0), ATOMIC_INIT(0)
#else
#define __RWSEM_DEBUG_INIT	/* */
#endif

#define __RWSEM_INITIALIZER(name,count) \
{ ATOMIC_INIT(count), 0, 0, 0, 0, __WAIT_QUEUE_HEAD_INITIALIZER((name).wait), \
	__WAIT_QUEUE_HEAD_INITIALIZER((name).write_bias_wait) \
	__SEM_DEBUG_INIT(name) __RWSEM_DEBUG_INIT }

#define __DECLARE_RWSEM_GENERIC(name,count) \
	struct rw_semaphore name = __RWSEM_INITIALIZER(name,count)

#define DECLARE_RWSEM(name) __DECLARE_RWSEM_GENERIC(name,RW_LOCK_BIAS)
#define DECLARE_RWSEM_READ_LOCKED(name) __DECLARE_RWSEM_GENERIC(name,RW_LOCK_BIAS-1)
#define DECLARE_RWSEM_WRITE_LOCKED(name) __DECLARE_RWSEM_GENERIC(name,0)

extern inline void init_rwsem(struct rw_semaphore *sem)
{
	atomic_set(&sem->count, RW_LOCK_BIAS);
	sem->read_bias_granted = 0;
	sem->write_bias_granted = 0;
	init_waitqueue_head(&sem->wait);
	init_waitqueue_head(&sem->write_bias_wait);
#if WAITQUEUE_DEBUG
	sem->__magic = (long)&sem->__magic;
	atomic_set(&sem->readers, 0);
	atomic_set(&sem->writers, 0);
#endif
}

extern struct rw_semaphore *__down_read_failed(struct rw_semaphore *sem);
extern struct rw_semaphore *__down_write_failed(struct rw_semaphore *sem);
extern struct rw_semaphore *__rwsem_wake(struct rw_semaphore *sem);

extern inline void down_read(struct rw_semaphore *sem)
{
#if WAITQUEUE_DEBUG
	CHECK_MAGIC(sem->__magic);
#endif
	__down_op_read(sem, __down_read_failed);
#if WAITQUEUE_DEBUG
	if (sem->write_bias_granted)
		BUG();
	if (atomic_read(&sem->writers))
		BUG();
	atomic_inc(&sem->readers);
#endif
}

extern inline void down_write(struct rw_semaphore *sem)
{
#if WAITQUEUE_DEBUG
	CHECK_MAGIC(sem->__magic);
#endif
	__down_op_write(sem, __down_write_failed);
#if WAITQUEUE_DEBUG
	if (atomic_read(&sem->writers))
		BUG();
	if (atomic_read(&sem->readers))
		BUG();
	if (sem->read_bias_granted)
		BUG();
	if (sem->write_bias_granted)
		BUG();
	atomic_inc(&sem->writers);
#endif
}

extern inline void up_read(struct rw_semaphore *sem)
{
#if WAITQUEUE_DEBUG
	if (sem->write_bias_granted)
		BUG();
	if (atomic_read(&sem->writers))
		BUG();
	atomic_dec(&sem->readers);
#endif
	__up_op_read(sem, __rwsem_wake);
}

extern inline void up_write(struct rw_semaphore *sem)
{
#if WAITQUEUE_DEBUG
	if (sem->read_bias_granted)
		BUG();
	if (sem->write_bias_granted)
		BUG();
	if (atomic_read(&sem->readers))
		BUG();
	if (atomic_read(&sem->writers) != 1)
		BUG();
	atomic_dec(&sem->writers);
#endif
	__up_op_write(sem, __rwsem_wake);
}

#endif