LCOM1920-T02G10

/*        $NetBSD: rwlock.h,v 1.10 2010/02/08 09:54:27 skrll Exp $        */

/*-

 * Copyright (c) 2002, 2006, 2007, 2008 The NetBSD Foundation, Inc.

 * All rights reserved.

 *

 * This code is derived from software contributed to The NetBSD Foundation

 * by Jason R. Thorpe and Andrew Doran.

 *

 * 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 NETBSD FOUNDATION, INC. 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 FOUNDATION 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 _SYS_RWLOCK_H_

#define        _SYS_RWLOCK_H_

/*

 * The rwlock provides exclusive access when held as a "writer",

 * and shared access when held as a "reader".

 *

 * Architectures may optionally provide stubs for the following functions to

 * implement the easy (unlocked, no waiters) cases.  If these stubs are

 * provided, __HAVE_RW_STUBS should be defined.

 *

 *        rw_enter()

 *        rw_exit()

 *        rw_tryenter()

 */

#if defined(_KERNEL_OPT)

#include "opt_lockdebug.h"

#endif

#if !defined(_KERNEL)

#include <sys/types.h>

#include <sys/inttypes.h>

#endif

typedef enum krw_t {

        RW_READER = 0,

        RW_WRITER = 1

} krw_t;

typedef struct krwlock krwlock_t;

#ifdef __RWLOCK_PRIVATE

/*

 * Bits in the owner field of the lock that indicate lock state.  If the

 * WRITE_LOCKED bit is clear, then the owner field is actually a count of

 * the number of readers.  The rw_owner field is laid out like so:

 *

 *         N                    4        3        2        1        0

 *        +---------------------------------------------------------+

 *        | owner or read count | nodbug | wrlock | wrwant |  wait  |

 *        +---------------------------------------------------------+

 */

#define        RW_HAS_WAITERS                0x01UL        /* lock has waiters */

#define        RW_WRITE_WANTED                0x02UL        /* >= 1 waiter is a writer */

#define        RW_WRITE_LOCKED                0x04UL        /* lock is currently write locked */

#if defined(LOCKDEBUG)

#define        RW_NODEBUG                0x08UL        /* LOCKDEBUG disabled */

#else

#define        RW_NODEBUG                0x00UL        /* do nothing */

#endif        /* LOCKDEBUG */

#define        RW_READ_COUNT_SHIFT        4

#define        RW_READ_INCR                (1UL << RW_READ_COUNT_SHIFT)

#define        RW_THREAD                ((uintptr_t)-RW_READ_INCR)

#define        RW_OWNER(rw)                ((rw)->rw_owner & RW_THREAD)

#define        RW_COUNT(rw)                ((rw)->rw_owner & RW_THREAD)

#define        RW_FLAGS(rw)                ((rw)->rw_owner & ~RW_THREAD)

void        rw_vector_enter(krwlock_t *, const krw_t);

void        rw_vector_exit(krwlock_t *);

int        rw_vector_tryenter(krwlock_t *, const krw_t);

#endif        /* __RWLOCK_PRIVATE */

#include <machine/rwlock.h>

#ifdef _KERNEL

void        rw_init(krwlock_t *);

void        rw_destroy(krwlock_t *);

int        rw_tryenter(krwlock_t *, const krw_t);

int        rw_tryupgrade(krwlock_t *);

void        rw_downgrade(krwlock_t *);

int        rw_read_held(krwlock_t *);

int        rw_write_held(krwlock_t *);

int        rw_lock_held(krwlock_t *);

void        rw_enter(krwlock_t *, const krw_t);

void        rw_exit(krwlock_t *);

void        rw_obj_init(void);

krwlock_t *rw_obj_alloc(void);

void        rw_obj_hold(krwlock_t *);

bool        rw_obj_free(krwlock_t *);

#endif        /* _KERNEL */

#endif /* _SYS_RWLOCK_H_ */