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read write lock
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#include <pthread.h> | |
struct rwlock { | |
pthread_mutex_t lock; | |
pthread_cond_t read, write; | |
unsigned readers, writers, read_waiters, write_waiters; | |
}; | |
void reader_lock(struct rwlock *self) { | |
pthread_mutex_lock(&self->lock); | |
if (self->writers || self->write_waiters) { | |
self->read_waiters++; | |
do pthread_cond_wait(&self->read, &self->lock); | |
while (self->writers || self->write_waiters); | |
self->read_waiters--; | |
} | |
self->readers++; | |
pthread_mutex_unlock(&self->lock); | |
} | |
void reader_unlock(struct rwlock *self) { | |
pthread_mutex_lock(&self->lock); | |
self->readers--; | |
if (self->write_waiters) | |
pthread_cond_signal(&self->write); | |
pthread_mutex_unlock(&self->lock); | |
} | |
void writer_lock(struct rwlock *self) { | |
pthread_mutex_lock(&self->lock); | |
if (self->readers || self->writers) { | |
self->write_waiters++; | |
do pthread_cond_wait(&self->write, &self->lock); | |
while (self->readers || self->writers); | |
self->write_waiters--; | |
} | |
self->writers = 1; | |
pthread_mutex_unlock(&self->lock); | |
} | |
void writer_unlock(struct rwlock *self) { | |
pthread_mutex_lock(&self->lock); | |
self->writers = 0; | |
if (self->write_waiters) | |
pthread_cond_signal(&self->write); | |
else if (self->read_waiters) | |
pthread_cond_broadcast(&self->read); | |
pthread_mutex_unlock(&self->lock); | |
} | |
void rwlock_init(struct rwlock *self) { | |
self->readers = self->writers = self->read_waiters = self->write_waiters = 0; | |
pthread_mutex_init(&self->lock, NULL); | |
pthread_cond_init(&self->read, NULL); | |
pthread_cond_init(&self->write, NULL); | |
} |
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