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Annotation of kernel/bsd/sys/lock.h, revision 1.1

1.1     ! root        1: /*
        !             2:  * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
        !             3:  *
        !             4:  * @APPLE_LICENSE_HEADER_START@
        !             5:  * 
        !             6:  * Portions Copyright (c) 1999 Apple Computer, Inc.  All Rights
        !             7:  * Reserved.  This file contains Original Code and/or Modifications of
        !             8:  * Original Code as defined in and that are subject to the Apple Public
        !             9:  * Source License Version 1.1 (the "License").  You may not use this file
        !            10:  * except in compliance with the License.  Please obtain a copy of the
        !            11:  * License at http://www.apple.com/publicsource and read it before using
        !            12:  * this file.
        !            13:  * 
        !            14:  * The Original Code and all software distributed under the License are
        !            15:  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
        !            16:  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
        !            17:  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
        !            18:  * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
        !            19:  * License for the specific language governing rights and limitations
        !            20:  * under the License.
        !            21:  * 
        !            22:  * @APPLE_LICENSE_HEADER_END@
        !            23:  */
        !            24: 
        !            25: /* Copyright (c) 1995, 1997 Apple Computer, Inc. All Rights Reserved */
        !            26: /* 
        !            27:  * Copyright (c) 1995
        !            28:  *     The Regents of the University of California.  All rights reserved.
        !            29:  *
        !            30:  * This code contains ideas from software contributed to Berkeley by
        !            31:  * Avadis Tevanian, Jr., Michael Wayne Young, and the Mach Operating
        !            32:  * System project at Carnegie-Mellon University.
        !            33:  *
        !            34:  * Redistribution and use in source and binary forms, with or without
        !            35:  * modification, are permitted provided that the following conditions
        !            36:  * are met:
        !            37:  * 1. Redistributions of source code must retain the above copyright
        !            38:  *    notice, this list of conditions and the following disclaimer.
        !            39:  * 2. Redistributions in binary form must reproduce the above copyright
        !            40:  *    notice, this list of conditions and the following disclaimer in the
        !            41:  *    documentation and/or other materials provided with the distribution.
        !            42:  * 3. All advertising materials mentioning features or use of this software
        !            43:  *    must display the following acknowledgement:
        !            44:  *     This product includes software developed by the University of
        !            45:  *     California, Berkeley and its contributors.
        !            46:  * 4. Neither the name of the University nor the names of its contributors
        !            47:  *    may be used to endorse or promote products derived from this software
        !            48:  *    without specific prior written permission.
        !            49:  *
        !            50:  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
        !            51:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
        !            52:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
        !            53:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
        !            54:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
        !            55:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
        !            56:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
        !            57:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
        !            58:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
        !            59:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
        !            60:  * SUCH DAMAGE.
        !            61:  *
        !            62:  *     @(#)lock.h      8.12 (Berkeley) 5/19/95
        !            63:  */
        !            64: 
        !            65: #ifndef        _SYS_LOCK_H_
        !            66: #define        _SYS_LOCK_H_
        !            67: 
        !            68: #include <mach/machine/simple_lock.h>
        !            69: 
        !            70: /*
        !            71:  * The general lock structure.  Provides for multiple shared locks,
        !            72:  * upgrading from shared to exclusive, and sleeping until the lock
        !            73:  * can be gained. The simple locks are defined in <machine/param.h>.
        !            74:  */
        !            75: struct lock__bsd__ {
        !            76:        simple_lock_data_t
        !            77:                lk_interlock;           /* lock on remaining fields */
        !            78:        u_int   lk_flags;               /* see below */
        !            79:        int     lk_sharecount;          /* # of accepted shared locks */
        !            80:        int     lk_waitcount;           /* # of processes sleeping for lock */
        !            81:        short   lk_exclusivecount;      /* # of recursive exclusive locks */
        !            82:        short   lk_prio;                /* priority at which to sleep */
        !            83:        char    *lk_wmesg;              /* resource sleeping (for tsleep) */
        !            84:        int     lk_timo;                /* maximum sleep time (for tsleep) */
        !            85:        pid_t   lk_lockholder;          /* pid of exclusive lock holder */
        !            86:        void    *lk_lockthread;         /* thread which acquired excl lock */
        !            87: };
        !            88: /*
        !            89:  * Lock request types:
        !            90:  *   LK_SHARED - get one of many possible shared locks. If a process
        !            91:  *     holding an exclusive lock requests a shared lock, the exclusive
        !            92:  *     lock(s) will be downgraded to shared locks.
        !            93:  *   LK_EXCLUSIVE - stop further shared locks, when they are cleared,
        !            94:  *     grant a pending upgrade if it exists, then grant an exclusive
        !            95:  *     lock. Only one exclusive lock may exist at a time, except that
        !            96:  *     a process holding an exclusive lock may get additional exclusive
        !            97:  *     locks if it explicitly sets the LK_CANRECURSE flag in the lock
        !            98:  *     request, or if the LK_CANRECUSE flag was set when the lock was
        !            99:  *     initialized.
        !           100:  *   LK_UPGRADE - the process must hold a shared lock that it wants to
        !           101:  *     have upgraded to an exclusive lock. Other processes may get
        !           102:  *     exclusive access to the resource between the time that the upgrade
        !           103:  *     is requested and the time that it is granted.
        !           104:  *   LK_EXCLUPGRADE - the process must hold a shared lock that it wants to
        !           105:  *     have upgraded to an exclusive lock. If the request succeeds, no
        !           106:  *     other processes will have gotten exclusive access to the resource
        !           107:  *     between the time that the upgrade is requested and the time that
        !           108:  *     it is granted. However, if another process has already requested
        !           109:  *     an upgrade, the request will fail (see error returns below).
        !           110:  *   LK_DOWNGRADE - the process must hold an exclusive lock that it wants
        !           111:  *     to have downgraded to a shared lock. If the process holds multiple
        !           112:  *     (recursive) exclusive locks, they will all be downgraded to shared
        !           113:  *     locks.
        !           114:  *   LK_RELEASE - release one instance of a lock.
        !           115:  *   LK_DRAIN - wait for all activity on the lock to end, then mark it
        !           116:  *     decommissioned. This feature is used before freeing a lock that
        !           117:  *     is part of a piece of memory that is about to be freed.
        !           118:  *
        !           119:  * These are flags that are passed to the lockmgr routine.
        !           120:  */
        !           121: #define LK_TYPE_MASK   0x0000000f      /* type of lock sought */
        !           122: #define LK_SHARED      0x00000001      /* shared lock */
        !           123: #define LK_EXCLUSIVE   0x00000002      /* exclusive lock */
        !           124: #define LK_UPGRADE     0x00000003      /* shared-to-exclusive upgrade */
        !           125: #define LK_EXCLUPGRADE 0x00000004      /* first shared-to-exclusive upgrade */
        !           126: #define LK_DOWNGRADE   0x00000005      /* exclusive-to-shared downgrade */
        !           127: #define LK_RELEASE     0x00000006      /* release any type of lock */
        !           128: #define LK_DRAIN       0x00000007      /* wait for all lock activity to end */
        !           129: /*
        !           130:  * External lock flags.
        !           131:  *
        !           132:  * The first three flags may be set in lock_init to set their mode permanently,
        !           133:  * or passed in as arguments to the lock manager. The LK_REENABLE flag may be
        !           134:  * set only at the release of a lock obtained by drain.
        !           135:  */
        !           136: #define LK_EXTFLG_MASK 0x00000070      /* mask of external flags */
        !           137: #define LK_NOWAIT      0x00000010      /* do not sleep to await lock */
        !           138: #define LK_SLEEPFAIL   0x00000020      /* sleep, then return failure */
        !           139: #define LK_CANRECURSE  0x00000040      /* allow recursive exclusive lock */
        !           140: #define LK_REENABLE    0x00000080      /* lock is be reenabled after drain */
        !           141: /*
        !           142:  * Internal lock flags.
        !           143:  *
        !           144:  * These flags are used internally to the lock manager.
        !           145:  */
        !           146: #define LK_WANT_UPGRADE        0x00000100      /* waiting for share-to-excl upgrade */
        !           147: #define LK_WANT_EXCL   0x00000200      /* exclusive lock sought */
        !           148: #define LK_HAVE_EXCL   0x00000400      /* exclusive lock obtained */
        !           149: #define LK_WAITDRAIN   0x00000800      /* process waiting for lock to drain */
        !           150: #define LK_DRAINING    0x00004000      /* lock is being drained */
        !           151: #define LK_DRAINED     0x00008000      /* lock has been decommissioned */
        !           152: /*
        !           153:  * Control flags
        !           154:  *
        !           155:  * Non-persistent external flags.
        !           156:  */
        !           157: #define LK_INTERLOCK   0x00010000      /* unlock passed simple lock after
        !           158:                                           getting lk_interlock */
        !           159: #define LK_RETRY       0x00020000      /* vn_lock: retry until locked */
        !           160: 
        !           161: /*
        !           162:  * Lock return status.
        !           163:  *
        !           164:  * Successfully obtained locks return 0. Locks will always succeed
        !           165:  * unless one of the following is true:
        !           166:  *     LK_FORCEUPGRADE is requested and some other process has already
        !           167:  *         requested a lock upgrade (returns EBUSY).
        !           168:  *     LK_WAIT is set and a sleep would be required (returns EBUSY).
        !           169:  *     LK_SLEEPFAIL is set and a sleep was done (returns ENOLCK).
        !           170:  *     PCATCH is set in lock priority and a signal arrives (returns
        !           171:  *         either EINTR or ERESTART if system calls is to be restarted).
        !           172:  *     Non-null lock timeout and timeout expires (returns EWOULDBLOCK).
        !           173:  * A failed lock attempt always returns a non-zero error value. No lock
        !           174:  * is held after an error return (in particular, a failed LK_UPGRADE
        !           175:  * or LK_FORCEUPGRADE will have released its shared access lock).
        !           176:  */
        !           177: 
        !           178: /*
        !           179:  * Indicator that no process holds exclusive lock
        !           180:  */
        !           181: #define LK_KERNPROC ((pid_t) -2)
        !           182: #define LK_NOPROC ((pid_t) -1)
        !           183: 
        !           184: struct proc;
        !           185: 
        !           186: void   lockinit __P((struct lock__bsd__ *, int prio, char *wmesg, int timo,
        !           187:                        int flags));
        !           188: int    lockmgr __P((struct lock__bsd__ *, u_int flags,
        !           189:                        simple_lock_t, struct proc *p));
        !           190: int    lockstatus __P((struct lock__bsd__ *));
        !           191: 
        !           192: #endif /* _SYS_LOCK_H_ */

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