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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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