| 1 | /* |
| 2 | * Copyright 2000, International Business Machines Corporation and others. |
| 3 | * All Rights Reserved. |
| 4 | * |
| 5 | * This software has been released under the terms of the IBM Public |
| 6 | * License. For details, see the LICENSE file in the top-level source |
| 7 | * directory or online at http://www.openafs.org/dl/license10.html |
| 8 | */ |
| 9 | |
| 10 | /*******************************************************************\ |
| 11 | * * |
| 12 | * Information Technology Center * |
| 13 | * Carnegie-Mellon University * |
| 14 | * * |
| 15 | * * |
| 16 | * * |
| 17 | \*******************************************************************/ |
| 18 | |
| 19 | |
| 20 | /* |
| 21 | Locking routines for Vice. |
| 22 | |
| 23 | */ |
| 24 | |
| 25 | #include <afsconfig.h> |
| 26 | #include <afs/param.h> |
| 27 | |
| 28 | #include <roken.h> |
| 29 | #include <afs/opr.h> |
| 30 | |
| 31 | #include "lwp.h" |
| 32 | #include "lock.h" |
| 33 | |
| 34 | #define FALSE 0 |
| 35 | #define TRUE 1 |
| 36 | |
| 37 | void |
| 38 | Lock_Init(struct Lock *lock) |
| 39 | { |
| 40 | lock->readers_reading = 0; |
| 41 | lock->excl_locked = 0; |
| 42 | lock->wait_states = 0; |
| 43 | lock->num_waiting = 0; |
| 44 | #ifdef AFS_PTHREAD_ENV |
| 45 | opr_mutex_init(&lock->mutex); |
| 46 | opr_cv_init(&lock->read_cv); |
| 47 | opr_cv_init(&lock->write_cv); |
| 48 | #endif /* AFS_PTHREAD_ENV */ |
| 49 | } |
| 50 | |
| 51 | void |
| 52 | Lock_Destroy(struct Lock *lock) |
| 53 | { |
| 54 | #ifdef AFS_PTHREAD_ENV |
| 55 | opr_mutex_destroy(&lock->mutex); |
| 56 | opr_cv_destroy(&lock->read_cv); |
| 57 | opr_cv_destroy(&lock->write_cv); |
| 58 | #endif /* AFS_PTHREAD_ENV */ |
| 59 | } |
| 60 | |
| 61 | void |
| 62 | Afs_Lock_Obtain(struct Lock *lock, int how) |
| 63 | { |
| 64 | switch (how) { |
| 65 | |
| 66 | case READ_LOCK: |
| 67 | lock->num_waiting++; |
| 68 | do { |
| 69 | lock->wait_states |= READ_LOCK; |
| 70 | #ifdef AFS_PTHREAD_ENV |
| 71 | opr_cv_wait(&lock->read_cv, &lock->mutex); |
| 72 | #else /* AFS_PTHREAD_ENV */ |
| 73 | LWP_WaitProcess(&lock->readers_reading); |
| 74 | #endif /* AFS_PTHREAD_ENV */ |
| 75 | } while (lock->excl_locked & WRITE_LOCK); |
| 76 | lock->num_waiting--; |
| 77 | lock->readers_reading++; |
| 78 | break; |
| 79 | |
| 80 | case WRITE_LOCK: |
| 81 | lock->num_waiting++; |
| 82 | do { |
| 83 | lock->wait_states |= WRITE_LOCK; |
| 84 | #ifdef AFS_PTHREAD_ENV |
| 85 | opr_cv_wait(&lock->write_cv, &lock->mutex); |
| 86 | #else /* AFS_PTHREAD_ENV */ |
| 87 | LWP_WaitProcess(&lock->excl_locked); |
| 88 | #endif /* AFS_PTHREAD_ENV */ |
| 89 | } while (lock->excl_locked || lock->readers_reading); |
| 90 | lock->num_waiting--; |
| 91 | lock->excl_locked = WRITE_LOCK; |
| 92 | break; |
| 93 | |
| 94 | case SHARED_LOCK: |
| 95 | lock->num_waiting++; |
| 96 | do { |
| 97 | lock->wait_states |= SHARED_LOCK; |
| 98 | #ifdef AFS_PTHREAD_ENV |
| 99 | opr_cv_wait(&lock->write_cv, &lock->mutex); |
| 100 | #else /* AFS_PTHREAD_ENV */ |
| 101 | LWP_WaitProcess(&lock->excl_locked); |
| 102 | #endif /* AFS_PTHREAD_ENV */ |
| 103 | } while (lock->excl_locked); |
| 104 | lock->num_waiting--; |
| 105 | lock->excl_locked = SHARED_LOCK; |
| 106 | break; |
| 107 | |
| 108 | case BOOSTED_LOCK: |
| 109 | lock->num_waiting++; |
| 110 | do { |
| 111 | lock->wait_states |= WRITE_LOCK; |
| 112 | #ifdef AFS_PTHREAD_ENV |
| 113 | opr_cv_wait(&lock->write_cv, &lock->mutex); |
| 114 | #else /* AFS_PTHREAD_ENV */ |
| 115 | LWP_WaitProcess(&lock->excl_locked); |
| 116 | #endif /* AFS_PTHREAD_ENV */ |
| 117 | } while (lock->readers_reading); |
| 118 | lock->num_waiting--; |
| 119 | lock->excl_locked = WRITE_LOCK; |
| 120 | break; |
| 121 | |
| 122 | default: |
| 123 | printf("Can't happen, bad LOCK type: %d\n", how); |
| 124 | opr_Assert(0); |
| 125 | } |
| 126 | } |
| 127 | |
| 128 | /* wake up readers waiting for this lock */ |
| 129 | void |
| 130 | Afs_Lock_WakeupR(struct Lock *lock) |
| 131 | { |
| 132 | if (lock->wait_states & READ_LOCK) { |
| 133 | lock->wait_states &= ~READ_LOCK; |
| 134 | #ifdef AFS_PTHREAD_ENV |
| 135 | opr_cv_broadcast(&lock->read_cv); |
| 136 | #else /* AFS_PTHREAD_ENV */ |
| 137 | LWP_NoYieldSignal(&lock->readers_reading); |
| 138 | #endif /* AFS_PTHREAD_ENV */ |
| 139 | } |
| 140 | } |
| 141 | |
| 142 | /* release a lock, giving preference to new readers */ |
| 143 | void |
| 144 | Afs_Lock_ReleaseR(struct Lock *lock) |
| 145 | { |
| 146 | if (lock->wait_states & READ_LOCK) { |
| 147 | lock->wait_states &= ~READ_LOCK; |
| 148 | #ifdef AFS_PTHREAD_ENV |
| 149 | opr_cv_broadcast(&lock->read_cv); |
| 150 | #else /* AFS_PTHREAD_ENV */ |
| 151 | LWP_NoYieldSignal(&lock->readers_reading); |
| 152 | #endif /* AFS_PTHREAD_ENV */ |
| 153 | } else { |
| 154 | lock->wait_states &= ~EXCL_LOCKS; |
| 155 | #ifdef AFS_PTHREAD_ENV |
| 156 | opr_cv_broadcast(&lock->write_cv); |
| 157 | #else /* AFS_PTHREAD_ENV */ |
| 158 | LWP_NoYieldSignal(&lock->excl_locked); |
| 159 | #endif /* AFS_PTHREAD_ENV */ |
| 160 | } |
| 161 | } |
| 162 | |
| 163 | /* release a lock, giving preference to new writers */ |
| 164 | void |
| 165 | Afs_Lock_ReleaseW(struct Lock *lock) |
| 166 | { |
| 167 | if (lock->wait_states & EXCL_LOCKS) { |
| 168 | lock->wait_states &= ~EXCL_LOCKS; |
| 169 | #ifdef AFS_PTHREAD_ENV |
| 170 | opr_cv_broadcast(&lock->write_cv); |
| 171 | #else /* AFS_PTHREAD_ENV */ |
| 172 | LWP_NoYieldSignal(&lock->excl_locked); |
| 173 | #endif /* AFS_PTHREAD_ENV */ |
| 174 | } else { |
| 175 | lock->wait_states &= ~READ_LOCK; |
| 176 | #ifdef AFS_PTHREAD_ENV |
| 177 | opr_cv_broadcast(&lock->read_cv); |
| 178 | #else /* AFS_PTHREAD_ENV */ |
| 179 | LWP_NoYieldSignal(&lock->readers_reading); |
| 180 | #endif /* AFS_PTHREAD_ENV */ |
| 181 | } |
| 182 | } |
| 183 | |
| 184 | #ifndef AFS_PTHREAD_ENV |
| 185 | /* These next guys exist to provide an interface to drop a lock atomically with |
| 186 | * blocking. They're trivial to do in a non-preemptive LWP environment. |
| 187 | */ |
| 188 | |
| 189 | /* release a write lock and sleep on an address, atomically */ |
| 190 | void |
| 191 | LWP_WaitProcessR(void *addr, struct Lock *alock) |
| 192 | { |
| 193 | ReleaseReadLock(alock); |
| 194 | LWP_WaitProcess(addr); |
| 195 | } |
| 196 | |
| 197 | /* release a write lock and sleep on an address, atomically */ |
| 198 | void |
| 199 | LWP_WaitProcessW(void *addr, struct Lock *alock) |
| 200 | { |
| 201 | ReleaseWriteLock(alock); |
| 202 | LWP_WaitProcess(addr); |
| 203 | } |
| 204 | |
| 205 | /* release a write lock and sleep on an address, atomically */ |
| 206 | void |
| 207 | LWP_WaitProcessS(void *addr, struct Lock *alock) |
| 208 | { |
| 209 | ReleaseSharedLock(alock); |
| 210 | LWP_WaitProcess(addr); |
| 211 | } |
| 212 | #endif /* AFS_PTHREAD_ENV */ |