pthread_join(ptid1,NULL);
pthread_join(ptid2,NULL);
printf("sum %d\n", cnt.sum);
pthread_mutex_destroy(&(cnt.lock));
return 0;
} 信号量
sync模块中的信号量： SyncSemaphore文档中显示，它和Mutex的不同之处，在于Semaphore一次可以被多个进程(或线程)得到，而Mutex一次只能被一个得到。所以在SyncSemaphore的构造函数中，有一个参数指定信号量可以被多少进程得到。
public SyncSemaphore::__construct ([ string $name [, integer $initialval [, bool $autounlock ]]] ) 就是这个$initialval (initial value)
$lock = new SyncSemaphore("UniqueName", 2);
for($i=0; $i0){
echo "parent process \n";
}else{
echo "child process {$i} is born. \n";
obtainLock($lock, $i);
}
}
while (pcntl_waitpid(0, $status) != -1) {
$status = pcntl_wexitstatus($status);
echo "Child $status completed\n";
}
function obtainLock ($lock, $i){
echo "process {$i} is getting the lock \n";
$res = $lock->lock(200);
sleep(1);
if (!$res){
echo "process {$i} unable to lock lock. \n";
}else{
echo "process {$i} successfully got the lock \n";
$lock->unlock();
}
exit();
}
这时候两个进程都能得到锁。
sysvsem模块中的信号量
sem_get 创建信号量
sem_remove 删除信号量（一般不用）
sem_acquire 请求得到信号量
sem_release 释放信号量。和 sem_acquire 成对使用。
$key = ftok('/tmp', 'c');
$sem = sem_get($key);
for($i=0; $i0){
//echo "parent process \n";
}else{
echo "child process {$i} is born. \n";
obtainLock($sem, $i);
}
}
while (pcntl_waitpid(0, $status) != -1) {
$status = pcntl_wexitstatus($status);
echo "Child $status completed\n";
}
sem_remove($sem); // finally remove the sem
function obtainLock ($sem, $i){
echo "process {$i} is getting the sem \n";
$res = sem_acquire($sem, true);
sleep(1);
if (!$res){
echo "process {$i} unable to get sem. \n";
}else{
echo "process {$i} successfully got the sem \n";
sem_release($sem);
}
exit();
}
这里有一个问题，sem_acquire()第二个参数$nowait默认为false，阻塞。我设为了true，如果得到锁失败，那么后面的sem_release会报警告 PHP Warning: sem_release(): SysV semaphore 4 (key 0x63000081) is not currently acquired in /home/jason/sysvsem.php on line 33, 所以这里的release操作必须放在得到锁的情况下执行，前面的几个例子中没有这个问题，没得到锁执行release也不会报错。当然最好还是成对出现，确保得到锁的情况下再release。
此外，ftok这个方法的参数有必要说明下，第一个 必须是existing, accessable的文件, 一般使用项目中的文件，第二个是单字符字符串。返回一个int。
输出为
parent process
parent process
child process 1 is born.
process 1 is getting the mutex
child process 0 is born.
process 0 is getting the mutex
process 1 successfully got the mutex
Child 0 completed
process 0 unable to lock mutex.
Child 0 completed