/*-
 * Copyright (c) 2007 Pawel Jakub Dawidek <pjd@FreeBSD.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#ifndef _OPENSOLARIS_SYS_RWLOCK_H_
#define _OPENSOLARIS_SYS_RWLOCK_H_

#include <sys/param.h>
#include <sys/proc.h>
#include <sys/lock.h>
#include <sys/sx.h>

#ifdef _KERNEL

typedef enum {
        RW_DEFAULT = 4          /* kernel default rwlock */
} krw_type_t;

typedef enum {
        RW_WRITER,
        RW_READER
} krw_t;

typedef struct sx       krwlock_t;

#ifndef OPENSOLARIS_WITNESS
#define RW_FLAGS        (SX_DUPOK | SX_NOWITNESS)
#else
#define RW_FLAGS        (SX_DUPOK)
#endif

#define RW_READ_HELD(x)         (rw_read_held((x)))
#define RW_WRITE_HELD(x)        (rw_write_held((x)))
#define RW_LOCK_HELD(x)         (rw_lock_held((x)))
#define RW_ISWRITER(x)          (rw_iswriter(x))

#define rw_init(lock, desc, type, arg)  do {                            \
        const char *_name;                                              \
        ASSERT((type) == 0 || (type) == RW_DEFAULT);                    \
        KASSERT(((lock)->lock_object.lo_flags & LO_ALLMASK) !=          \
            LO_EXPECTED, ("lock %s already initialized", #lock));       \
        bzero((lock), sizeof(struct sx));                               \
        for (_name = #lock; *_name != '\0'; _name++) {                  \
                if (*_name >= 'a' && *_name <= 'z')                     \
                        break;                                          \
        }                                                               \
        if (*_name == '\0')                                             \
                _name = #lock;                                          \
        sx_init_flags((lock), _name, RW_FLAGS);                         \
} while (0)
#define rw_destroy(lock)        sx_destroy(lock)
#define rw_enter(lock, how)     do {                                    \
        if ((how) == RW_READER)                                         \
                sx_slock(lock);                                         \
        else /* if ((how) == RW_WRITER) */                              \
                sx_xlock(lock);                                         \
} while (0)
#define rw_tryenter(lock, how)  ((how) == RW_READER ? sx_try_slock(lock) : sx_try_xlock(lock))
#define rw_exit(lock)           sx_unlock(lock)
#define rw_downgrade(lock)      sx_downgrade(lock)
#define rw_tryupgrade(lock)     sx_try_upgrade(lock)
#define rw_read_held(lock)      ((lock)->sx_lock != SX_LOCK_UNLOCKED && ((lock)->sx_lock & SX_LOCK_SHARED))
#define rw_write_held(lock)     sx_xlocked(lock)
#define rw_lock_held(lock)      (rw_read_held(lock) || rw_write_held(lock))
#define rw_iswriter(lock)       sx_xlocked(lock)
#define rw_owner(lock)          sx_xholder(lock)

#endif  /* defined(_KERNEL) */

#endif  /* _OPENSOLARIS_SYS_RWLOCK_H_ */