2 * LWKT_RWLOCK.C (MP SAFE)
4 * Copyright (c) 2003,2004 The DragonFly Project. All rights reserved.
6 * This code is derived from software contributed to The DragonFly Project
7 * by Matthew Dillon <dillon@backplane.com>
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in
17 * the documentation and/or other materials provided with the
19 * 3. Neither the name of The DragonFly Project nor the names of its
20 * contributors may be used to endorse or promote products derived
21 * from this software without specific, prior written permission.
23 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
24 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
25 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
26 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
27 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
28 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
29 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
30 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
31 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
32 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
33 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
36 * Implements simple shared/exclusive locks using LWKT.
38 * $DragonFly: src/sys/kern/Attic/lwkt_rwlock.c,v 1.8 2005/06/20 07:31:05 dillon Exp $
41 #include <sys/param.h>
42 #include <sys/systm.h>
43 #include <sys/kernel.h>
45 #include <sys/rtprio.h>
46 #include <sys/queue.h>
47 #include <sys/thread2.h>
50 * lwkt_rwlock_init() (MP SAFE)
52 * NOTE! called from low level boot, we cannot do anything fancy.
55 lwkt_rwlock_init(lwkt_rwlock_t lock)
57 lwkt_wait_init(&lock->rw_wait);
58 lock->rw_owner = NULL;
60 lock->rw_requests = 0;
64 * lwkt_rwlock_uninit() (MP SAFE)
67 lwkt_rwlock_uninit(lwkt_rwlock_t lock)
73 * lwkt_exlock() (MP SAFE)
75 * NOTE: We need to use a critical section in addition to the token to
76 * interlock against IPI lwkt_schedule calls which may manipulate the
77 * rw_wait structure's list. This is because the IPI runs in the context of
78 * the current thread and thus cannot use any token calls (if it did the
79 * token would just share with the thread's token and not provide any
80 * protection). This needs a rewrite.
83 lwkt_exlock(lwkt_rwlock_t lock, const char *wmesg)
88 lwkt_gettoken(&ilock, &lock->rw_token);
90 gen = lock->rw_wait.wa_gen;
91 while (lock->rw_owner != curthread) {
92 if (lock->rw_owner == NULL && lock->rw_count == 0) {
93 lock->rw_owner = curthread;
97 lwkt_block(&lock->rw_wait, wmesg, &gen);
101 lwkt_reltoken(&ilock);
106 * lwkt_shlock() (MP SAFE)
109 lwkt_shlock(lwkt_rwlock_t lock, const char *wmesg)
114 lwkt_gettoken(&ilock, &lock->rw_token);
116 gen = lock->rw_wait.wa_gen;
117 while (lock->rw_owner != NULL) {
119 lwkt_block(&lock->rw_wait, wmesg, &gen);
123 lwkt_reltoken(&ilock);
128 * lwkt_exunlock() (MP SAFE)
131 lwkt_exunlock(lwkt_rwlock_t lock)
135 lwkt_gettoken(&ilock, &lock->rw_token);
137 KASSERT(lock->rw_owner != NULL, ("lwkt_exunlock: shared lock"));
138 KASSERT(lock->rw_owner == curthread, ("lwkt_exunlock: not owner"));
139 if (--lock->rw_count == 0) {
140 lock->rw_owner = NULL;
141 if (lock->rw_requests)
142 lwkt_signal(&lock->rw_wait, 1);
144 lwkt_reltoken(&ilock);
149 * lwkt_shunlock() (MP SAFE)
152 lwkt_shunlock(lwkt_rwlock_t lock)
156 lwkt_gettoken(&ilock, &lock->rw_token);
158 KASSERT(lock->rw_owner == NULL, ("lwkt_shunlock: exclusive lock"));
159 if (--lock->rw_count == 0) {
160 if (lock->rw_requests)
161 lwkt_signal(&lock->rw_wait, 1);
163 lwkt_reltoken(&ilock);