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Annotation of Net2/vm/lock.h, revision 1.1

1.1     ! root        1: /* 
        !             2:  * Copyright (c) 1991 Regents of the University of California.
        !             3:  * All rights reserved.
        !             4:  *
        !             5:  * This code is derived from software contributed to Berkeley by
        !             6:  * The Mach Operating System project at Carnegie-Mellon University.
        !             7:  *
        !             8:  * Redistribution and use in source and binary forms, with or without
        !             9:  * modification, are permitted provided that the following conditions
        !            10:  * are met:
        !            11:  * 1. Redistributions of source code must retain the above copyright
        !            12:  *    notice, this list of conditions and the following disclaimer.
        !            13:  * 2. Redistributions in binary form must reproduce the above copyright
        !            14:  *    notice, this list of conditions and the following disclaimer in the
        !            15:  *    documentation and/or other materials provided with the distribution.
        !            16:  * 3. All advertising materials mentioning features or use of this software
        !            17:  *    must display the following acknowledgement:
        !            18:  *     This product includes software developed by the University of
        !            19:  *     California, Berkeley and its contributors.
        !            20:  * 4. Neither the name of the University nor the names of its contributors
        !            21:  *    may be used to endorse or promote products derived from this software
        !            22:  *    without specific prior written permission.
        !            23:  *
        !            24:  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
        !            25:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
        !            26:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
        !            27:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
        !            28:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
        !            29:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
        !            30:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
        !            31:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
        !            32:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
        !            33:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
        !            34:  * SUCH DAMAGE.
        !            35:  *
        !            36:  *     @(#)lock.h      7.3 (Berkeley) 4/21/91
        !            37:  *
        !            38:  *
        !            39:  * Copyright (c) 1987, 1990 Carnegie-Mellon University.
        !            40:  * All rights reserved.
        !            41:  *
        !            42:  * Authors: Avadis Tevanian, Jr., Michael Wayne Young
        !            43:  * 
        !            44:  * Permission to use, copy, modify and distribute this software and
        !            45:  * its documentation is hereby granted, provided that both the copyright
        !            46:  * notice and this permission notice appear in all copies of the
        !            47:  * software, derivative works or modified versions, and any portions
        !            48:  * thereof, and that both notices appear in supporting documentation.
        !            49:  * 
        !            50:  * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS" 
        !            51:  * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND 
        !            52:  * FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
        !            53:  * 
        !            54:  * Carnegie Mellon requests users of this software to return to
        !            55:  *
        !            56:  *  Software Distribution Coordinator  or  [email protected]
        !            57:  *  School of Computer Science
        !            58:  *  Carnegie Mellon University
        !            59:  *  Pittsburgh PA 15213-3890
        !            60:  *
        !            61:  * any improvements or extensions that they make and grant Carnegie the
        !            62:  * rights to redistribute these changes.
        !            63:  */
        !            64: 
        !            65: /*
        !            66:  *     Locking primitives definitions
        !            67:  */
        !            68: 
        !            69: #ifndef        _LOCK_H_
        !            70: #define        _LOCK_H_
        !            71: 
        !            72: #define        NCPUS   1               /* XXX */
        !            73: 
        !            74: /*
        !            75:  *     A simple spin lock.
        !            76:  */
        !            77: 
        !            78: struct slock {
        !            79:        int             lock_data;      /* in general 1 bit is sufficient */
        !            80: };
        !            81: 
        !            82: typedef struct slock   simple_lock_data_t;
        !            83: typedef struct slock   *simple_lock_t;
        !            84: 
        !            85: /*
        !            86:  *     The general lock structure.  Provides for multiple readers,
        !            87:  *     upgrading from read to write, and sleeping until the lock
        !            88:  *     can be gained.
        !            89:  */
        !            90: 
        !            91: struct lock {
        !            92: #ifdef vax
        !            93:        /*
        !            94:         *      Efficient VAX implementation -- see field description below.
        !            95:         */
        !            96:        unsigned int    read_count:16,
        !            97:                        want_upgrade:1,
        !            98:                        want_write:1,
        !            99:                        waiting:1,
        !           100:                        can_sleep:1,
        !           101:                        :0;
        !           102: 
        !           103:        simple_lock_data_t      interlock;
        !           104: #else  vax
        !           105: #ifdef ns32000
        !           106:        /*
        !           107:         *      Efficient ns32000 implementation --
        !           108:         *      see field description below.
        !           109:         */
        !           110:        simple_lock_data_t      interlock;
        !           111:        unsigned int    read_count:16,
        !           112:                        want_upgrade:1,
        !           113:                        want_write:1,
        !           114:                        waiting:1,
        !           115:                        can_sleep:1,
        !           116:                        :0;
        !           117: 
        !           118: #else  ns32000
        !           119:        /*      Only the "interlock" field is used for hardware exclusion;
        !           120:         *      other fields are modified with normal instructions after
        !           121:         *      acquiring the interlock bit.
        !           122:         */
        !           123:        simple_lock_data_t
        !           124:                        interlock;      /* Interlock for remaining fields */
        !           125:        boolean_t       want_write;     /* Writer is waiting, or locked for write */
        !           126:        boolean_t       want_upgrade;   /* Read-to-write upgrade waiting */
        !           127:        boolean_t       waiting;        /* Someone is sleeping on lock */
        !           128:        boolean_t       can_sleep;      /* Can attempts to lock go to sleep */
        !           129:        int             read_count;     /* Number of accepted readers */
        !           130: #endif /* ns32000 */
        !           131: #endif /* vax */
        !           132:        char            *thread;        /* Thread that has lock, if recursive locking allowed */
        !           133:                                        /* (should be thread_t, but but we then have mutually
        !           134:                                           recursive definitions) */
        !           135:        int             recursion_depth;/* Depth of recursion */
        !           136: };
        !           137: 
        !           138: typedef struct lock    lock_data_t;
        !           139: typedef struct lock    *lock_t;
        !           140: 
        !           141: #if    NCPUS > 1
        !           142: void           simple_lock_init();
        !           143: void           simple_lock();
        !           144: void           simple_unlock();
        !           145: boolean_t      simple_lock_try();
        !           146: #else  NCPUS > 1
        !           147: /*
        !           148:  *     No multiprocessor locking is necessary.
        !           149:  */
        !           150: #define simple_lock_init(l)
        !           151: #define simple_lock(l)
        !           152: #define simple_unlock(l)
        !           153: #define simple_lock_try(l)     (1)     /* always succeeds */
        !           154: #endif /* NCPUS > 1 */
        !           155: 
        !           156: /* Sleep locks must work even if no multiprocessing */
        !           157: 
        !           158: void           lock_init();
        !           159: void           lock_sleepable();
        !           160: void           lock_write();
        !           161: void           lock_read();
        !           162: void           lock_done();
        !           163: boolean_t      lock_read_to_write();
        !           164: void           lock_write_to_read();
        !           165: boolean_t      lock_try_write();
        !           166: boolean_t      lock_try_read();
        !           167: boolean_t      lock_try_read_to_write();
        !           168: 
        !           169: #define        lock_read_done(l)       lock_done(l)
        !           170: #define        lock_write_done(l)      lock_done(l)
        !           171: 
        !           172: void           lock_set_recursive();
        !           173: void           lock_clear_recursive();
        !           174: 
        !           175: #endif /* !_LOCK_H_ */

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