4. API 比较细节

4.7.2 读者/写者锁

读者/写者锁允许多于一个的线索，同时读一个变量；使用此类型的锁，在某一时刻仅有一个线索能访问变量以修改它。

• Solaris API

#include <synch.h>

int rwlock_init (rwlock_t *rwlp, int type, void *arg)

int rwlock_destroy (rwlock_t *rwlp)

int rw_rdlock (rwlock_t *rwlp)

int rw_wrlock (rwlock_t *rwlp)

int rw_unlock (rwlock_t *rwlp)

int rw_tryrdlock (rwlock_t *rwlp)

int rw_trywrlock (rwlock_t *rwlp)

• 用进程内部的范围初始化读者/写者锁

rwlock_t rwlp;

int ret;

ret = rwlock_init (&rwlp, USYNC_THREAD, 0); /* to be used within this process only */

• 用进程间的范围初始化读者/写者锁

rwlock_t rwlp;

int ret;

ret = rwlock_init (&rwlp, USYNC_PROCESS, 0); /* to be used among all processes */

• 释放一个读者/写者锁

rwlock_t rwlp;

int ret;

ret = rwlock_destroy(&rwlp); /* rwlock is destroyed */

• 读者/写者锁上锁

rwlock_t rwlp;

int ret;

ret = rw_rdlock (&rwlp); /* acquire the rwlock for reading */

ret = rw_wrlock (&rwlp); /* acquire the rwlock for writing */

• 读者/写者锁解锁

rwlock_t rwlp;

int ret;

ret = rw_unlock (&rwlp); /* release the rwlock */

• 读者/写者锁尝试上锁

rwlock_t rwlp;

int ret;

ret = rw_tryrdlock (&rwlp); /* try to grab rwlock for reading */

ret = rw_trywrlock (&rwlp); /* try to grab rwlock for writing */

Copyright: NPACT