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Direktori : /usr/src/kernels/3.10.0-1160.88.1.el7.centos.plus.x86_64/include/asm-generic/
Current File : //usr/src/kernels/3.10.0-1160.88.1.el7.centos.plus.x86_64/include/asm-generic/rwsem.h
#ifndef _ASM_POWERPC_RWSEM_H
#define _ASM_POWERPC_RWSEM_H

#ifndef _LINUX_RWSEM_H
#error "Please don't include <asm/rwsem.h> directly, use <linux/rwsem.h> instead."
#endif

#ifdef __KERNEL__

/*
 * R/W semaphores for PPC using the stuff in lib/rwsem.c.
 * Adapted largely from include/asm-i386/rwsem.h
 * by Paul Mackerras <paulus@samba.org>.
 */

/*
 * the semaphore definition
 */
#ifdef CONFIG_PPC64
# define RWSEM_ACTIVE_MASK		0xffffffffL
#else
# define RWSEM_ACTIVE_MASK		0x0000ffffL
#endif

#define RWSEM_UNLOCKED_VALUE		0x00000000L
#define RWSEM_ACTIVE_BIAS		0x00000001L
#define RWSEM_WAITING_BIAS		(-RWSEM_ACTIVE_MASK-1)
#define RWSEM_ACTIVE_READ_BIAS		RWSEM_ACTIVE_BIAS
#define RWSEM_ACTIVE_WRITE_BIAS		(RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)

/*
 * lock for reading
 */
static inline void __down_read(struct rw_semaphore *sem)
{
	if (unlikely(atomic_long_inc_return((atomic_long_t *)&sem->count) <= 0))
		rwsem_down_read_failed(sem);
}

static inline int __down_read_trylock(struct rw_semaphore *sem)
{
	long tmp;

	while ((tmp = atomic_long_read(&sem->count)) >= 0) {
		if (tmp == atomic_long_cmpxchg(&sem->count, tmp,
				   tmp + RWSEM_ACTIVE_READ_BIAS)) {
			return 1;
		}
	}
	return 0;
}

/*
 * lock for writing
 */
static inline void __down_write_nested(struct rw_semaphore *sem, int subclass)
{
	long tmp;

	tmp = atomic_long_add_return(RWSEM_ACTIVE_WRITE_BIAS,
				     (atomic_long_t *)&sem->count);
	if (unlikely(tmp != RWSEM_ACTIVE_WRITE_BIAS))
		rwsem_down_write_failed(sem);
}

static inline void __down_write(struct rw_semaphore *sem)
{
	__down_write_nested(sem, 0);
}

static inline int __down_write_trylock(struct rw_semaphore *sem)
{
	long tmp;

	tmp = atomic_long_cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE,
		      RWSEM_ACTIVE_WRITE_BIAS);
	return tmp == RWSEM_UNLOCKED_VALUE;
}

/*
 * unlock after reading
 */
static inline void __up_read(struct rw_semaphore *sem)
{
	long tmp;

	tmp = atomic_long_dec_return((atomic_long_t *)&sem->count);
	if (unlikely(tmp < -1 && (tmp & RWSEM_ACTIVE_MASK) == 0))
		rwsem_wake(sem);
}

/*
 * unlock after writing
 */
static inline void __up_write(struct rw_semaphore *sem)
{
	if (unlikely(atomic_long_sub_return(RWSEM_ACTIVE_WRITE_BIAS,
				 (atomic_long_t *)&sem->count) < 0))
		rwsem_wake(sem);
}

/*
 * downgrade write lock to read lock
 */
static inline void __downgrade_write(struct rw_semaphore *sem)
{
	long tmp;

	tmp = atomic_long_add_return(-RWSEM_WAITING_BIAS,
				     (atomic_long_t *)&sem->count);
	if (tmp < 0)
		rwsem_downgrade_wake(sem);
}

#endif	/* __KERNEL__ */
#endif	/* _ASM_POWERPC_RWSEM_H */
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