使用C3P0-0.9.1.jar包的问题：APPARENT DEADLOCK!!! Creating emergency threads for unassigned pending tasks!

from: http://blog.csdn.net/dingherry/article/details/6534494
C3P0-0.9.1.jar包的问题出现了：

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2011-06-09 16:15:57.500 [com.mchange.v2.c3p0.C3P0Registry]-[INFO] Initializing c3p0-0.9.1 [built 16-January-2007 14:46:42; debug? true; trace: 10]

2011-06-09 16:15:57.640 [com.mchange.v2.c3p0.impl.AbstractPoolBackedDataSource]-[INFO] Initializing c3p0 pool... com.mchange.v2.c3p0.PoolBackedDataSource@6e6ed172 [ connectionPoolDataSource -> com.mchange.v2.c3p0.WrapperConnectionPoolDataSource@68581fed [ acquireIncrement
-> 3, acquireRetryAttempts -> 30, acquireRetryDelay -> 1000, autoCommitOnClose -> false, automaticTestTable -> null, breakAfterAcquireFailure -> false, checkoutTimeout -> 0, connectionCustomizerClassName -> null, connectionTesterClassName -> com.mchange.v2.c3p0.impl.DefaultConnectionTester,
debugUnreturnedConnectionStackTraces -> false, factoryClassLocation -> null, forceIgnoreUnresolvedTransactions -> false, identityToken -> 1bqc2na8gw1f1seoboglg|9bb04a, idleConnectionTestPeriod -> 0, initialPoolSize -> 20, maxAdministrativeTaskTime -> 0, maxConnectionAge
-> 0, maxIdleTime -> 5000, maxIdleTimeExcessConnections -> 0, maxPoolSize -> 50, maxStatements -> 100, maxStatementsPerConnection -> 0, minPoolSize -> 20, nestedDataSource -> com.mchange.v2.c3p0.DriverManagerDataSource@96b27bd3 [ description -> null, driverClass
-> null, factoryClassLocation -> null, identityToken -> 1bqc2na8gw1f1seoboglg|15a6bd5, jdbcUrl -> jdbc:oracle:thin:@172.7.19.70:1521:orcl, properties -> {user=******, password=******, autocommit=false, release_mode=auto} ], preferredTestQuery -> null, propertyCycle
-> 0, testConnectionOnCheckin -> false, testConnectionOnCheckout -> false, unreturnedConnectionTimeout -> 0, usesTraditionalReflectiveProxies -> false; userOverrides: {} ], dataSourceName -> null, factoryClassLocation -> null, identityToken -> 1bqc2na8gw1f1seoboglg|730333,
numHelperThreads -> 3 ]

2011-06-09 16:16:17.640 [com.mchange.v2.async.ThreadPoolAsynchronousRunner]-[WARN] com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector@689af4 -- APPARENT DEADLOCK!!! Creating emergency threads for unassigned pending tasks!

2011-06-09 16:16:17.640 [com.mchange.v2.async.ThreadPoolAsynchronousRunner]-[WARN] com.mchange.v2.async.ThreadPoolAsynchronousRunner$DeadlockDetector@689af4 -- APPARENT DEADLOCK!!! Complete Status:

Managed Threads: 3

Active Threads: 3

Active Tasks:

com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@13c6c41 (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#0)

com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@1e74f39 (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#1)

com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@1023cad (com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#2)

Pending Tasks:

com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@1dd8a94

com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@1b51005

com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@2ec051

com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@15422a8

com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@af4653

com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@1321f9b

com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@1b8ffe1

com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@a738be

com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@7e7592

com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@58d3e2

com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@1be9a9b

com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@985ae9

com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@7890f2

com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@17418ba

com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@10379d4

com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@1336fab

com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask@1e85079

Pool thread stack traces:

Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#0,5,main]

java.net.PlainSocketImpl.socketConnect(Native Method)

java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:333)

java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:195)

java.net.PlainSocketImpl.connect(PlainSocketImpl.java:182)

java.net.SocksSocketImpl.connect(SocksSocketImpl.java:366)

java.net.Socket.connect(Socket.java:525)

java.net.Socket.connect(Socket.java:475)

java.net.Socket.<init>(Socket.java:372)

java.net.Socket.<init>(Socket.java:186)

oracle.net.nt.TcpNTAdapter.connect(Unknown Source)

oracle.net.nt.ConnOption.connect(Unknown Source)

oracle.net.nt.ConnStrategy.execute(Unknown Source)

oracle.net.resolver.AddrResolution.resolveAndExecute(Unknown Source)

oracle.net.ns.NSProtocol.establishConnection(Unknown Source)

oracle.net.ns.NSProtocol.connect(Unknown Source)

oracle.jdbc.driver.T4CConnection.connect(T4CConnection.java:843)

oracle.jdbc.driver.T4CConnection.logon(T4CConnection.java:267)

oracle.jdbc.driver.PhysicalConnection.<init>(PhysicalConnection.java:413)

oracle.jdbc.driver.T4CConnection.<init>(T4CConnection.java:164)

oracle.jdbc.driver.T4CDriverExtension.getConnection(T4CDriverExtension.java:34)

oracle.jdbc.driver.OracleDriver.connect(OracleDriver.java:752)

com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:135)

com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:182)

com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:171)

com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:137)

com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:1014)

com.mchange.v2.resourcepool.BasicResourcePool.access$800(BasicResourcePool.java:32)

com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask.run(BasicResourcePool.java:1810)

com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:547)

Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#1,5,main]

java.net.PlainSocketImpl.socketConnect(Native Method)

java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:333)

java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:195)

java.net.PlainSocketImpl.connect(PlainSocketImpl.java:182)

java.net.SocksSocketImpl.connect(SocksSocketImpl.java:366)

java.net.Socket.connect(Socket.java:525)

java.net.Socket.connect(Socket.java:475)

java.net.Socket.<init>(Socket.java:372)

java.net.Socket.<init>(Socket.java:186)

oracle.net.nt.TcpNTAdapter.connect(Unknown Source)

oracle.net.nt.ConnOption.connect(Unknown Source)

oracle.net.nt.ConnStrategy.execute(Unknown Source)

oracle.net.resolver.AddrResolution.resolveAndExecute(Unknown Source)

oracle.net.ns.NSProtocol.establishConnection(Unknown Source)

oracle.net.ns.NSProtocol.connect(Unknown Source)

oracle.jdbc.driver.T4CConnection.connect(T4CConnection.java:843)

oracle.jdbc.driver.T4CConnection.logon(T4CConnection.java:267)

oracle.jdbc.driver.PhysicalConnection.<init>(PhysicalConnection.java:413)

oracle.jdbc.driver.T4CConnection.<init>(T4CConnection.java:164)

oracle.jdbc.driver.T4CDriverExtension.getConnection(T4CDriverExtension.java:34)

oracle.jdbc.driver.OracleDriver.connect(OracleDriver.java:752)

com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:135)

com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:182)

com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:171)

com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:137)

com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:1014)

com.mchange.v2.resourcepool.BasicResourcePool.access$800(BasicResourcePool.java:32)

com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask.run(BasicResourcePool.java:1810)

com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:547)

Thread[com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread-#2,5,main]

java.net.PlainSocketImpl.socketConnect(Native Method)

java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:333)

java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:195)

java.net.PlainSocketImpl.connect(PlainSocketImpl.java:182)

java.net.SocksSocketImpl.connect(SocksSocketImpl.java:366)

java.net.Socket.connect(Socket.java:525)

java.net.Socket.connect(Socket.java:475)

java.net.Socket.<init>(Socket.java:372)

java.net.Socket.<init>(Socket.java:186)

oracle.net.nt.TcpNTAdapter.connect(Unknown Source)

oracle.net.nt.ConnOption.connect(Unknown Source)

oracle.net.nt.ConnStrategy.execute(Unknown Source)

oracle.net.resolver.AddrResolution.resolveAndExecute(Unknown Source)

oracle.net.ns.NSProtocol.establishConnection(Unknown Source)

oracle.net.ns.NSProtocol.connect(Unknown Source)

oracle.jdbc.driver.T4CConnection.connect(T4CConnection.java:843)

oracle.jdbc.driver.T4CConnection.logon(T4CConnection.java:267)

oracle.jdbc.driver.PhysicalConnection.<init>(PhysicalConnection.java:413)

oracle.jdbc.driver.T4CConnection.<init>(T4CConnection.java:164)

oracle.jdbc.driver.T4CDriverExtension.getConnection(T4CDriverExtension.java:34)

oracle.jdbc.driver.OracleDriver.connect(OracleDriver.java:752)

com.mchange.v2.c3p0.DriverManagerDataSource.getConnection(DriverManagerDataSource.java:135)

com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:182)

com.mchange.v2.c3p0.WrapperConnectionPoolDataSource.getPooledConnection(WrapperConnectionPoolDataSource.java:171)

com.mchange.v2.c3p0.impl.C3P0PooledConnectionPool$1PooledConnectionResourcePoolManager.acquireResource(C3P0PooledConnectionPool.java:137)

com.mchange.v2.resourcepool.BasicResourcePool.doAcquire(BasicResourcePool.java:1014)

com.mchange.v2.resourcepool.BasicResourcePool.access$800(BasicResourcePool.java:32)

com.mchange.v2.resourcepool.BasicResourcePool$AcquireTask.run(BasicResourcePool.java:1810)

com.mchange.v2.async.ThreadPoolAsynchronousRunner$PoolThread.run(ThreadPoolAsynchronousRunner.java:547)

参考比较全的算：http://japi.iteye.com/blog/243702
http://www.dotobe.com/2010/10/tomcat-c3p0连接池问题，apparent-deadlock/ http://muzso.hu/2011/05/06/hibernate-c3p0-and-robust-database-connection-handling http://agodika.com/mblog/tech/2011/02/16/fixing-c3p0-apparent-deadlock-problem/
SSH项目，设置hibernate.properties里的hibernate.c3p0.max_statements为0，重启tomcat好了。

这个C3P0的bug，存在着，并且一直存在着，其作者现在貌似无能为力，希望有人能突破这一瓶颈。