rwsem.h

嵌入式系统设计与实例开发源码

#ifndef _ALPHA_RWSEM_H
#define _ALPHA_RWSEM_H

/*
 * Written by Ivan Kokshaysky <[e-mail]>, 2001.
 * Based on asm-alpha/semaphore.h and asm-i386/rwsem.h
 */

#ifndef _LINUX_RWSEM_H
#error please dont include asm/rwsem.h directly, use linux/rwsem.h instead
#endif

#ifdef __KERNEL__

#include <linux/compiler.h>
#include <linux/list.h>
#include <linux/spinlock.h>

struct rwsem_waiter;

extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *sem);
extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *sem);
extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *);

/*
 * the semaphore definition
 */
struct rw_semaphore {
	long			count;
#define RWSEM_UNLOCKED_VALUE		0x0000000000000000L
#define RWSEM_ACTIVE_BIAS		0x0000000000000001L
#define RWSEM_ACTIVE_MASK		0x00000000ffffffffL
#define RWSEM_WAITING_BIAS		(-0x0000000100000000L)
#define RWSEM_ACTIVE_READ_BIAS		RWSEM_ACTIVE_BIAS
#define RWSEM_ACTIVE_WRITE_BIAS		(RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
	spinlock_t		wait_lock;
	struct list_head	wait_list;
#if RWSEM_DEBUG
	int			debug;
#endif
};

#if RWSEM_DEBUG
#define __RWSEM_DEBUG_INIT      , 0
#else
#define __RWSEM_DEBUG_INIT	/* */
#endif

#define __RWSEM_INITIALIZER(name) \
	{ RWSEM_UNLOCKED_VALUE, SPIN_LOCK_UNLOCKED, \
	LIST_HEAD_INIT((name).wait_list) __RWSEM_DEBUG_INIT }

#define DECLARE_RWSEM(name) \
	struct rw_semaphore name = __RWSEM_INITIALIZER(name)

static inline void init_rwsem(struct rw_semaphore *sem)
{
	sem->count = RWSEM_UNLOCKED_VALUE;
	spin_lock_init(&sem->wait_lock);
	INIT_LIST_HEAD(&sem->wait_list);
#if RWSEM_DEBUG
	sem->debug = 0;
#endif
}

static inline void __down_read(struct rw_semaphore *sem)
{
	long oldcount;
#ifndef	CONFIG_SMP
	oldcount = sem->count;
	sem->count += RWSEM_ACTIVE_READ_BIAS;
#else
	long temp;
	__asm__ __volatile__(
	"1:	ldq_l	%0,%1\n"
	"	addq	%0,%3,%2\n"
	"	stq_c	%2,%1\n"
	"	beq	%2,2f\n"
	"	mb\n"
	".subsection 2\n"
	"2:	br	1b\n"
	".previous"
	:"=&r" (oldcount), "=m" (sem->count), "=&r" (temp)
	:"Ir" (RWSEM_ACTIVE_READ_BIAS), "m" (sem->count) : "memory");
#endif
	if (__builtin_expect(oldcount < 0, 0))
		rwsem_down_read_failed(sem);
}

static inline void __down_write(struct rw_semaphore *sem)
{
	long oldcount;
#ifndef	CONFIG_SMP
	oldcount = sem->count;
	sem->count += RWSEM_ACTIVE_WRITE_BIAS;
#else
	long temp;
	__asm__ __volatile__(
	"1:	ldq_l	%0,%1\n"
	"	addq	%0,%3,%2\n"
	"	stq_c	%2,%1\n"
	"	beq	%2,2f\n"
	"	mb\n"
	".subsection 2\n"
	"2:	br	1b\n"
	".previous"
	:"=&r" (oldcount), "=m" (sem->count), "=&r" (temp)
	:"Ir" (RWSEM_ACTIVE_WRITE_BIAS), "m" (sem->count) : "memory");
#endif
	if (__builtin_expect(oldcount, 0))
		rwsem_down_write_failed(sem);
}

static inline void __up_read(struct rw_semaphore *sem)
{
	long oldcount;
#ifndef	CONFIG_SMP
	oldcount = sem->count;
	sem->count -= RWSEM_ACTIVE_READ_BIAS;
#else
	long temp;
	__asm__ __volatile__(
	"	mb\n"
	"1:	ldq_l	%0,%1\n"
	"	subq	%0,%3,%2\n"
	"	stq_c	%2,%1\n"
	"	beq	%2,2f\n"
	".subsection 2\n"
	"2:	br	1b\n"
	".previous"
	:"=&r" (oldcount), "=m" (sem->count), "=&r" (temp)
	:"Ir" (RWSEM_ACTIVE_READ_BIAS), "m" (sem->count) : "memory");
#endif
	if (__builtin_expect(oldcount < 0, 0)) 
		if ((int)oldcount - RWSEM_ACTIVE_READ_BIAS == 0)
			rwsem_wake(sem);
}

static inline void __up_write(struct rw_semaphore *sem)
{
	long count;
#ifndef	CONFIG_SMP
	sem->count -= RWSEM_ACTIVE_WRITE_BIAS;
	count = sem->count;
#else
	long temp;
	__asm__ __volatile__(
	"	mb\n"
	"1:	ldq_l	%0,%1\n"
	"	subq	%0,%3,%2\n"
	"	stq_c	%2,%1\n"
	"	beq	%2,2f\n"
	"	subq	%0,%3,%0\n"
	".subsection 2\n"
	"2:	br	1b\n"
	".previous"
	:"=&r" (count), "=m" (sem->count), "=&r" (temp)
	:"Ir" (RWSEM_ACTIVE_WRITE_BIAS), "m" (sem->count) : "memory");
#endif
	if (__builtin_expect(count, 0))
		if ((int)count == 0)
			rwsem_wake(sem);
}

static inline void rwsem_atomic_add(long val, struct rw_semaphore *sem)
{
#ifndef	CONFIG_SMP
	sem->count += val;
#else
	long temp;
	__asm__ __volatile__(
	"1:	ldq_l	%0,%1\n"
	"	addq	%0,%2,%0\n"
	"	stq_c	%0,%1\n"
	"	beq	%0,2f\n"
	".subsection 2\n"
	"2:	br	1b\n"
	".previous"
	:"=&r" (temp), "=m" (sem->count)
	:"Ir" (val), "m" (sem->count));
#endif
}

static inline long rwsem_atomic_update(long val, struct rw_semaphore *sem)
{
#ifndef	CONFIG_SMP
	sem->count += val;
	return sem->count;
#else
	long ret, temp;
	__asm__ __volatile__(
	"1:	ldq_l	%0,%1\n"
	"	addq 	%0,%3,%2\n"
	"	addq	%0,%3,%0\n"
	"	stq_c	%2,%1\n"
	"	beq	%2,2f\n"
	".subsection 2\n"
	"2:	br	1b\n"
	".previous"
	:"=&r" (ret), "=m" (sem->count), "=&r" (temp)
	:"Ir" (val), "m" (sem->count));

	return ret;
#endif
}

#endif /* __KERNEL__ */
#endif /* _ALPHA_RWSEM_H */