117 lines
2.9 KiB
C
117 lines
2.9 KiB
C
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#include <libdfa/rw.h>
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rwl *initlock (void)
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{
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rwl *lock;
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lock = (rwl *)malloc (sizeof (rwl));
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if (lock == NULL) return (NULL);
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lock->mut = (pthread_mutex_t *) malloc (sizeof (pthread_mutex_t));
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if (lock->mut == NULL) { free (lock); return (NULL); }
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lock->writeOK =
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(pthread_cond_t *) malloc (sizeof (pthread_cond_t));
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if (lock->writeOK == NULL) { free (lock->mut); free (lock);
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return (NULL); }
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lock->readOK =
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(pthread_cond_t *) malloc (sizeof (pthread_cond_t));
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if (lock->writeOK == NULL) { free (lock->mut); free (lock->writeOK);
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free (lock); return (NULL); }
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pthread_mutex_init (lock->mut, NULL);
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pthread_cond_init (lock->writeOK, NULL);
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pthread_cond_init (lock->readOK, NULL);
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lock->readers = 0;
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lock->writers = 0;
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lock->waiting = 0;
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return (lock);
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}
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/*void readlock(rwl *lock, int d) {
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writelock(lock, d);
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}*/
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void readlock (rwl *lock, int d)
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{
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/* printf("reader %d\n", d); */
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fflush(NULL);
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pthread_mutex_lock (lock->mut);
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if (lock->writers || lock->waiting) {
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do {
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/* printf ("reader %d blocked. %d readers, %d writers, %d waiting\n", d, lock->readers, lock->writers, lock->waiting); */
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pthread_cond_wait (lock->readOK, lock->mut);
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/* printf ("reader %d unblocked.\n", d); */
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} while (lock->writers);
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}
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lock->readers++;
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pthread_mutex_unlock (lock->mut);
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/* printf("reader %d done\n", d); */
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fflush(NULL);
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return;
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}
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void writelock (rwl *lock, int d)
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{
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/* printf("\nwritelock %d\n", d); */
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fflush(NULL);
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pthread_mutex_lock (lock->mut);
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lock->waiting++;
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while (lock->readers || lock->writers) {
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/* printf ("writer %d blocked. %d readers, %d writers, %d waiting\n", d, lock->readers, lock->writers, lock->waiting); */
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pthread_cond_wait (lock->writeOK, lock->mut);
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/* printf ("writer %d unblocked.\n", d); */
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}
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lock->waiting--;
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lock->writers++;
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pthread_mutex_unlock (lock->mut);
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/* printf("\nwritelock %d done\n", d); */
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fflush(NULL);
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return;
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}
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/*void readunlock(rwl *lock) {
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writeunlock(lock);
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}*/
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void readunlock (rwl *lock)
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{
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pthread_mutex_lock (lock->mut);
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lock->readers--;
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pthread_cond_signal (lock->writeOK);
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/* Don't need to broadcast, since only one writer can run at
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once. */
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/* pthread_cond_broadcast (lock->writeOK); */
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pthread_mutex_unlock (lock->mut);
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/* printf("readunlock done\n"); */
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}
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void writeunlock (rwl *lock)
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{
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/* printf("writeunlock done\n"); */
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fflush(NULL);
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pthread_mutex_lock (lock->mut);
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lock->writers--;
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/* Need this as well (in case there's another writer, which is blocking the all of the readers. */
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pthread_cond_signal (lock->writeOK);
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pthread_cond_broadcast (lock->readOK);
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pthread_mutex_unlock (lock->mut);
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}
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void deletelock (rwl *lock)
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{
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pthread_mutex_destroy (lock->mut);
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pthread_cond_destroy (lock->readOK);
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pthread_cond_destroy (lock->writeOK);
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free (lock);
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return;
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}
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