2 * LWKT_RWLOCK.C (MP SAFE)
4 * Copyright (c) 2003-2006 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>
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10 * modification, are permitted provided that the following conditions
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36 * Implements simple shared/exclusive locks using LWKT.
38 * $DragonFly: src/sys/kern/Attic/lwkt_rwlock.c,v 1.11 2006/05/21 20:23:25 dillon Exp $
41 #include <sys/param.h>
42 #include <sys/systm.h>
43 #include <sys/kernel.h>
44 #include <sys/spinlock.h>
46 #include <sys/rtprio.h>
47 #include <sys/queue.h>
48 #include <sys/thread2.h>
49 #include <sys/spinlock2.h>
52 * lwkt_rwlock_init() (MP SAFE)
54 * NOTE! called from low level boot, we cannot do anything fancy.
57 lwkt_rwlock_init(lwkt_rwlock_t lock)
59 lwkt_wait_init(&lock->rw_wait);
60 lock->rw_owner = NULL;
62 lock->rw_requests = 0;
66 * lwkt_rwlock_uninit() (MP SAFE)
69 lwkt_rwlock_uninit(lwkt_rwlock_t lock)
75 * lwkt_exlock() (MP SAFE)
77 * NOTE: We need to use a critical section in addition to the token to
78 * interlock against IPI lwkt_schedule calls which may manipulate the
79 * rw_wait structure's list. This is because the IPI runs in the context of
80 * the current thread and thus cannot use any token calls (if it did the
81 * token would just share with the thread's token and not provide any
82 * protection). This needs a rewrite.
85 lwkt_exlock(lwkt_rwlock_t lock, const char *wmesg)
89 spin_lock_wr(&lock->rw_spinlock);
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 spin_unlock_wr(&lock->rw_spinlock);
98 lwkt_block(&lock->rw_wait, wmesg, &gen);
99 spin_lock_wr(&lock->rw_spinlock);
103 spin_unlock_wr(&lock->rw_spinlock);
107 * lwkt_shlock() (MP SAFE)
110 lwkt_shlock(lwkt_rwlock_t lock, const char *wmesg)
114 spin_lock_wr(&lock->rw_spinlock);
115 gen = lock->rw_wait.wa_gen;
116 while (lock->rw_owner != NULL) {
118 spin_unlock_wr(&lock->rw_spinlock);
119 lwkt_block(&lock->rw_wait, wmesg, &gen);
120 spin_lock_wr(&lock->rw_spinlock);
124 spin_unlock_wr(&lock->rw_spinlock);
128 * lwkt_exunlock() (MP SAFE)
131 lwkt_exunlock(lwkt_rwlock_t lock)
133 KASSERT(lock->rw_owner != NULL, ("lwkt_exunlock: shared lock"));
134 KASSERT(lock->rw_owner == curthread, ("lwkt_exunlock: not owner"));
135 spin_lock_wr(&lock->rw_spinlock);
136 if (--lock->rw_count == 0) {
137 lock->rw_owner = NULL;
138 if (lock->rw_requests) {
139 spin_unlock_wr(&lock->rw_spinlock);
140 lwkt_signal(&lock->rw_wait, 1);
144 spin_unlock_wr(&lock->rw_spinlock);
148 * lwkt_shunlock() (MP SAFE)
151 lwkt_shunlock(lwkt_rwlock_t lock)
153 KASSERT(lock->rw_owner == NULL, ("lwkt_shunlock: exclusive lock"));
154 spin_lock_wr(&lock->rw_spinlock);
155 if (--lock->rw_count == 0) {
156 if (lock->rw_requests) {
157 spin_unlock_wr(&lock->rw_spinlock);
158 lwkt_signal(&lock->rw_wait, 1);
162 spin_unlock_wr(&lock->rw_spinlock);