Warning: exec() [function.exec]: Unable to fork，配置git的webhook的问题

我的服务器是阿里云的Win server 2008
git托管仓库是coding，我配置的hook.php内容是
exec("git pull", $array2);var_export($array2);
但是页面返回
Warning: exec() [function.exec]: Unable to fork [git pull]
这是为什么呢？
求助？

回复内容：

我的服务器是阿里云的Win server 2008
git托管仓库是coding，我配置的hook.php内容是
exec("git pull", $array2);var_export($array2);
但是页面返回
Warning: exec() [function.exec]: Unable to fork [git pull]
这是为什么呢？
求助？

可能是资源被耗尽

Forking means in this case the operation to create a new process using the fork() system call. fork() usually failes because necessary system resources are exhausted, it is likely that memory limits or the maximum number of open processes per system is reached.

源自http://stackoverflow.com/questions/20732394/what-does-the-unable-to-fork-error-mean