c3p0 连接池APPARENT DEADLOCK

最近发现系统经常会出现APPARENT DEADLOCK 的错误，如下

DEBUG|16:15:07,278| GenericDao:568 - Hql:  FROM LoginSession l WHERE l.sessionToken = ?
DEBUG|16:15:09,905| GenericDao:568 - Hql:  FROM LoginSession l WHERE l.sessionToken = ?
WARN |16:15:23,125| ThreadPoolAsynchronousRunner:608 - com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector@649948aa -- APPARENT DEADLOCK!!! Creating emergency threads for unassigned pending tasks!
WARN |16:15:23,158| ThreadPoolAsynchronousRunner:624 - com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector@649948aa -- APPARENT DEADLOCK!!! Complete Status:
        Managed Threads: 3
        Active Threads: 3
        Active Tasks:

发现是参数maxStatements和numHelperThreads所致的，
maxStatement太大会导致这个异常，
可以调整maxStatements为一个小点的值， 然后增加numHelperThreads的数量， 就可以修复这个异常

来源：
http://laravel.iteye.com/