Added a file lock check during cache writing, as per suggestion at bug #3466
diff --git a/system/libraries/Output.php b/system/libraries/Output.php
index 781e368..98a941a 100644
--- a/system/libraries/Output.php
+++ b/system/libraries/Output.php
@@ -389,9 +389,16 @@
 		

 		$expire = time() + ($this->cache_expiration * 60);

 		

-		flock($fp, LOCK_EX);

-		fwrite($fp, $expire.'TS--->'.$output);

-		flock($fp, LOCK_UN);

+		if (flock($fp, LOCK_EX))

+		{

+			fwrite($fp, $expire.'TS--->'.$output);

+			flock($fp, LOCK_UN);

+		}

+		else

+		{

+			log_message('error', "Unable to secure a file lock for file at: ".$cache_path);

+			return;

+		}

 		fclose($fp);

 		@chmod($cache_path, DIR_WRITE_MODE);