php - 在 PHP 中使用共享内存时出现意外错误(PHP 警告 : shmop_open(): unable to attach or create shared memory segment 'Invalid argument' )

Question

我刚开始在PHP中使用共享内存来做一些事情。这是我的代码。

 <?php
//limit the task to be forked
$task = 100;
$process_pool = array();
//allocate 1kb memory segment to store process_pool
$process_pool_key = ftok(__FILE__,chr(0));
$process_pool_shm = shmop_open($process_pool_key,'c',0644,1024);
$datas = array();
for($i = 1; $i<= $task; $i++) {
    $pid = pcntl_fork();
    if ($pid == -1) {
        die("Can't fork child process.");
    }
    if ($pid == 0) {
        $current_pid = getmypid();
        $process_pool_size = shmop_size($process_pool_shm);
        $process_pool = @unserialize(shmop_read($process_pool_shm,0,$process_pool_size));
        //store child process data into specific memory
        $child_data  = array('pid'=>$current_pid,"data"=>[rand(),'hello']);
        $child_key = ftok(__FILE__,chr($current_pid));
   }

        $size = 1024*1024; 
        $child_shm = shmop_open($child_key,'c',0644,$size);
        shmop_write($child_shm,serialize($child_data),0);
        exit(0);
    } else {
       $process_pool[$pid] = array($pid);
       shmop_write($process_pool_shm,serialize($process_pool),0);
   }
}
while(pcntl_waitpid(-1,$status) > 0);
//Read data from all child process
foreach($process_pool as $pid => $pid_info) {
    $tmp_key = ftok(__FILE__,chr($pid));
    $size= 1024*1024;
    $tmp_shm  = shmop_open($tmp_key,'a',0644,$size);
    $org_data = shmop_read($tmp_shm,0,$size);
    $child_data = @unserialize($org_data);
    if (empty($child_data)) {
        echo "$tmp_key\n";
    }
    shmop_delete($tmp_shm);
    shmop_close($tmp_shm);
    if (!empty($child_data)) {
        $datas[$pid] = $child_data;
    }
}
var_dump(count($datas));
//var_dump(count($process_pool));
//var_dump(count(array_keys($datas)));
//var_dump(count(array_keys($process_pool)));
foreach (array_keys($process_pool) as $p_key) {
    if (!in_array($p_key,array_keys($datas))) {
        echo $p_key."\n";
    }
}
shmop_delete($process_pool_shm);
shmop_close($process_pool_shm);

上面的代码spaws了几个子进程，子进程各自持有自己的共享内存段，子进程的共享内存段用于存储处理后的数据，父进程会从子进程的共享内存中收集数据子进程完成后的片段。

In my humble opinion, this code should run without any problems. But some unexpected problems spat randomly.

有时进展顺利

/home/jhbian/pider/test/process/ReproduceProcessExample.php:60:
int(100)

有时会崩溃

 PHP Warning:  shmop_open(): unable to attach or create shared memory segment 'Invalid argument' in /home/jhbian/pider/test/process/ReproduceProcessExample.php on line 29
PHP Stack trace:
PHP   1. {main}() /home/jhbian/pider/test/process/ReproduceProcessExample.php:0
PHP   2. shmop_open() /home/jhbian/pider/test/process/ReproduceProcessExample.php:29

Warning: shmop_open(): unable to attach or create shared memory segment 'Invalid argument' in /home/jhbian/pider/test/process/ReproduceProcessExample.php on line 29

Call Stack:
    0.0002     366568   1. {main}() /home/jhbian/pider/test/process/ReproduceProcessExample.php:0
    0.0738     367872   2. shmop_open() /home/jhbian/pider/test/process/ReproduceProcessExample.php:29

PHP Warning:  shmop_write() expects parameter 1 to be resource, boolean given in /home/jhbian/pider/test/process/ReproduceProcessExample.php on line 30
PHP Stack trace:
PHP   1. {main}() /home/jhbian/pider/test/process/ReproduceProcessExample.php:0
PHP   2. shmop_write() /home/jhbian/pider/test/process/ReproduceProcessExample.php:30

Warning: shmop_write() expects parameter 1 to be resource, boolean given in /home/jhbian/pider/test/process/ReproduceProcessExample.php on line 30

Call Stack:
    0.0002     366568   1. {main}() /home/jhbian/pider/test/process/ReproduceProcessExample.php:0
    0.0755     368192   2. shmop_write() /home/jhbian/pider/test/process/ReproduceProcessExample.php:30

PHP Warning:  shmop_read(): count is out of range in /home/jhbian/pider/test/process/ReproduceProcessExample.php on line 49
PHP Stack trace:
PHP   1. {main}() /home/jhbian/pider/test/process/ReproduceProcessExample.php:0
PHP   2. shmop_read() /home/jhbian/pider/test/process/ReproduceProcessExample.php:49

Warning: shmop_read(): count is out of range in /home/jhbian/pider/test/process/ReproduceProcessExample.php on line 49

Call Stack:
    0.0002     366568   1. {main}() /home/jhbian/pider/test/process/ReproduceProcessExample.php:0
    0.1350    1551336   2. shmop_read() /home/jhbian/pider/test/process/ReproduceProcessExample.php:49

104785
/home/jhbian/pider/test/process/ReproduceProcessExample.php:60:
int(99)
16896

谁能指出铰链在哪里？

Answer 1

当您已经创建了新的共享内存段并且出于某种原因 PHP 没有关闭它时，就会发生这种情况。 您需要使用“w”标志访问已创建的段

$shared_memory = @shmop_open($key, "c", 0644, 255);
if (false === $shared_memory) {
    $shared_memory = shmop_open($key, "w", 0644, 255);
}