CacheEngineFiles::lock

protected function lock($fileName)
{

	$wouldBlock = 0;
	self::$lockHandles[$fileName] = @fopen($fileName, "r+");
	if (self::$lockHandles[$fileName])
	{
		flock(self::$lockHandles[$fileName], LOCK_EX | LOCK_NB, $wouldBlock);
		//$wouldBlock === 1 someone else has the lock.
	}
	return $wouldBlock !== 1;
}