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/* $OpenBSD: lock.h,v 1.6 1997/10/06 20:23:16 deraadt Exp $ */
/* $NetBSD: lock.h,v 1.8 1994/10/30 19:11:11 cgd Exp $ */
/*
* Copyright (c) 1991, 1993
* The Regents of the University of California. All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* The Mach Operating System project at Carnegie-Mellon University.
*
* 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.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
*
* @(#)lock.h 8.1 (Berkeley) 6/11/93
*
*
* Copyright (c) 1987, 1990 Carnegie-Mellon University.
* All rights reserved.
*
* Authors: Avadis Tevanian, Jr., Michael Wayne Young
*
* Permission to use, copy, modify and distribute this software and
* its documentation is hereby granted, provided that both the copyright
* notice and this permission notice appear in all copies of the
* software, derivative works or modified versions, and any portions
* thereof, and that both notices appear in supporting documentation.
*
* CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
* CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
* FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
*
* Carnegie Mellon requests users of this software to return to
*
* Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
* School of Computer Science
* Carnegie Mellon University
* Pittsburgh PA 15213-3890
*
* any improvements or extensions that they make and grant Carnegie the
* rights to redistribute these changes.
*/
/*
* Locking primitives definitions
*/
#ifndef _LOCK_H_
#define _LOCK_H_
#define NCPUS 1 /* XXX */
/*
* A simple spin lock.
*/
struct slock {
int lock_data; /* in general 1 bit is sufficient */
};
typedef struct slock simple_lock_data_t;
typedef struct slock *simple_lock_t;
/*
* The general lock structure. Provides for multiple readers,
* upgrading from read to write, and sleeping until the lock
* can be gained.
*/
struct lock {
#ifdef vax
/*
* Efficient VAX implementation -- see field description below.
*/
unsigned int read_count:16,
want_upgrade:1,
want_write:1,
waiting:1,
can_sleep:1,
:0;
simple_lock_data_t interlock;
#else /* vax */
#ifdef ns32000
/*
* Efficient ns32000 implementation --
* see field description below.
*/
simple_lock_data_t interlock;
unsigned int read_count:16,
want_upgrade:1,
want_write:1,
waiting:1,
can_sleep:1,
:0;
#else /* ns32000 */
/* Only the "interlock" field is used for hardware exclusion;
* other fields are modified with normal instructions after
* acquiring the interlock bit.
*/
simple_lock_data_t
interlock; /* Interlock for remaining fields */
boolean_t want_write; /* Writer is waiting, or locked for write */
boolean_t want_upgrade; /* Read-to-write upgrade waiting */
boolean_t waiting; /* Someone is sleeping on lock */
boolean_t can_sleep; /* Can attempts to lock go to sleep */
int read_count; /* Number of accepted readers */
#endif /* ns32000 */
#endif /* vax */
void *thread; /* Thread that has lock, if recursive locking allowed */
/* (should be thread_t, but but we then have mutually
recursive definitions) */
int recursion_depth;/* Depth of recursion */
};
typedef struct lock lock_data_t;
typedef struct lock *lock_t;
#if NCPUS > 1
__BEGIN_DECLS
void simple_lock __P((simple_lock_t));
void simple_lock_init __P((simple_lock_t));
boolean_t simple_lock_try __P((simple_lock_t));
void simple_unlock __P((simple_lock_t));
__END_DECLS
#else /* No multiprocessor locking is necessary. */
#define simple_lock(l)
#define simple_lock_init(l)
#define simple_lock_try(l) (1) /* Always succeeds. */
#define simple_unlock(l)
#endif
/* Sleep locks must work even if no multiprocessing. */
#define lock_read_done(l) lock_done(l)
#define lock_write_done(l) lock_done(l)
void lock_clear_recursive __P((lock_t));
void lock_done __P((lock_t));
void lock_init __P((lock_t, boolean_t));
void lock_read __P((lock_t));
boolean_t lock_read_to_write __P((lock_t));
void lock_set_recursive __P((lock_t));
void lock_sleepable __P((lock_t, boolean_t));
boolean_t lock_try_read __P((lock_t));
boolean_t lock_try_read_to_write __P((lock_t));
boolean_t lock_try_write __P((lock_t));
void lock_write __P((lock_t));
void lock_write_to_read __P((lock_t));
#endif /* !_LOCK_H_ */
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