在IBM JVM产生的javacore或者Threaddump文件中应用服务器Web容器的常见线程状态：

Idle线程：一个已经准备好接受请求的线程，但是没有和插件或者客户端建立连接
Keep-Alive线程：是一个已经准备好接受请求的线程，并且已经和插件或者客户端建立连接
正在接受请求的线程：是一个线程正在读取request的内容或者头部

下面就给出各种线程在javacore或者Threaddump中的表现形式：

Idle线程：
"Servlet.Engine.Transports : 20" (TID:0x427F190, sys_thread_t:0x15D175E8, state:R, native ID:0xBB8) prio=5
at java.lang.Object.wait(Native Method)
at java.lang.Object.wait(Object.java:429)
at com.ibm.ws.util.BoundedBuffer.take(BoundedBuffer.java:161)
at com.ibm.ws.util.ThreadPool.getTask(ThreadPool.java(Compiled Code)) at com.ibm.ws.util.ThreadPool$Worker.run(ThreadPool.java(Compiled Code))

Keep-alive线程 (非SSL模式)：
"Servlet.Engine.Transports : 20" (TID:0x427F190, sys_thread_t:0x15D175E8, state:R, native ID:0xBB8) prio=5
at java.net.SocketInputStream.socketRead(Native Method)
at java.net.SocketInputStream.read(SocketInputStream.java:86)
at com.ibm.ws.io.Stream.read(Stream.java)
at com.ibm.ws.io.ReadStream.readBuffer(ReadStream.java)
at com.ibm.ws.io.ReadStream.read(ReadStream.java)
at com.ibm.ws.http.HttpRequest.readRequestLine(HttpRequest.java)
at com.ibm.ws.http.HttpRequest.readRequest(HttpRequest.java)
at com.ibm.ws.http.HttpConnection.readAndHandleRequest(HttpConnection.java)
at com.ibm.ws.http.HttpConnection.run(HttpConnection.java)
at com.ibm.ws.util.CachedThread.run(ThreadPool.java)

Keep-alive线程 (SSL模式)：
"Servlet.Engine.Transports : 12" (TID:0x458DBA18, sys_thread_t:0x60B297C0, state:R, native ID:0x427E) prio=5
at java.net.SocketInputStream.socketRead(Native Method)
at java.net.SocketInputStream.read(SocketInputStream.java(Compiled Code))
at com.ibm.sslite.s.a(Unknown Source)(Compiled Code)
at com.ibm.sslite.s.b(Unknown Source)(Compiled Code)
at com.ibm.sslite.s.a(Unknown Source)(Compiled Code)
at com.ibm.sslite.a.read(Unknown Source)(Compiled Code)
at com.ibm.jsse.a.read(Unknown Source)(Compiled Code)
at com.ibm.ws.io.Stream.read(Stream.java(Compiled Code))
at com.ibm.ws.io.ReadStream.readBuffer(ReadStream.java(Inlined Compiled Code))
at com.ibm.ws.io.ReadStream.read(ReadStream.java(Inlined Compiled Code))
at com.ibm.ws.http.HttpRequest.readRequestLine(HttpRequest.java(Compiled Code))
at com.ibm.ws.http.HttpRequest.readRequest(HttpRequest.java(Compiled Code))
at com.ibm.ws.http.HttpConnection.readAndHandleRequest(HttpConnection)
at com.ibm.ws.http.HttpConnection.run(HttpConnection.java(Compiled Code))
at com.ibm.ws.util.ThreadPool$Worker.run(ThreadPool.java:672)


正在接受请求的线程：
at java.net.SocketInputStream.socketRead(Native Method)
at java.net.SocketInputStream.read(SocketInputStream.java:85)
at com.ibm.ws.io.Stream.read(Stream.java:17)
at com.ibm.ws.io.ReadStream.readBuffer(ReadStream.java:411)
at com.ibm.ws.io.ReadStream.read(ReadStream.java:110)
at com.ibm.ws.http.HttpConnection.run(HttpConnection.java:448)
at com.ibm.ws.util.ThreadPool$Worker.run(ThreadPool.java:672)

Sun JVM的常见线程状态：

对于thread dump信息，主要关注的是线程的状态和其执行堆栈
线程的状态一般为三类
Runnable（R）：当前可以运行的线程
Waiting on monitor（CW）：线程主动wait
Waiting for monitor entry（MW）：线程等锁
一般关注的都是第一和第三种状态的线程
Cpu很忙则关注runnable的线程
Cpu闲则关注waiting for monitor entry的线程
一种典型的死锁是由于在server端应用（比如servlet）中请求由同一weblogic实例server的资源
解决办法就是将该servlet放到另外的执行队列里去执行

下面给出一个典型的死锁线程（注意STUCK关键字）：

"[STUCK] ExecuteThread: '2' for queue: 'weblogic.kernel.Default (self-tuning)'" daemon prio=10 tid=02fe9a18 nid=35 lwp_id=7518924 runnable [440dd000..440db878]
 at java.net.SocketInputStream.socketRead0(Native Method)
 at java.net.SocketInputStream.read(SocketInputStream.java:134)
 at weblogic.jdbc.oracle.net8.OracleDataProvider.getArrayOfBytesFromSocket(Unknown Source)
 at weblogic.jdbc.oracle.net8.OracleDataProvider.readFirstPacketInBuffer(Unknown Source)
 at weblogic.jdbc.oracle.net8.OracleDataProvider.readPacket(Unknown Source)
 at weblogic.jdbc.oracle.net8.OracleDataProvider.receive(Unknown Source)
 at weblogic.jdbc.oracle.net8.OracleNet8NSPTDAPacket.sendRequest(Unknown Source)
 at weblogic.jdbc.oracle.OracleImplStatement.fetchNext(Unknown Source)
 at weblogic.jdbc.oracle.OracleImplStatement.fetchNext2(Unknown Source)
 at weblogic.jdbc.oracle.OracleImplResultset.fetchAtPosition(Unknown Source)
 at weblogic.jdbc.base.BaseImplResultSet.next(Unknown Source)
 at weblogic.jdbc.base.BaseResultSet.next(Unknown Source)
 - locked <55f25550> (a weblogic.jdbc.oracle.OracleConnection)
 at weblogic.jdbc.wrapper.ResultSet_weblogic_jdbc_base_BaseResultSet.next(Unknown Source)
 at org.hibernate.loader.Loader.doQuery(Loader.java:685)

UNIX/Linux下可用top、vmstat或prstat命令观察系统资源状况

 Mandy Chung's Blog 有一篇关于Thread Dump and Concurrency Locks的blog，摘来如下：

Thread dumps are very useful for diagnosing synchronization related problems such as deadlocks on object monitors. Ctrl-\ on Solaris/Linux or Ctrl-Break on Windows has been a common way to get a thread dump of a running application. On Solaris or Linux, you can send a QUIT signal to the target application. The target application in both cases prints a thread dump to the standard output and also detects if there is any deadlock involving object monitors.

jstack, a new troubleshooting utility introduced in Tiger (J2SE 5.0), provides another way to obtain a thread dump of an application. Alan Bateman has a nice blog about jstack and its several improvements in Mustang (Java SE 6). Mustang jstack works like a remote Ctrl-\ or Ctrl-Break if you are on Windows.

jconsole is JMX-complaint GUI tool which allows you to get a thread dump on the fly. The "Using JConsole to Monitor Applications" article gives you an overview of the Tiger monitoring and management functionality.

Mustang extends the thread dump, jstack, and jconsole to support java.util.concurrent.locks to improve its diagnosability. For example, the Threads tab in the Mustang jconsole now shows which synchronizer a thread is waiting to acquire when the thread is blocked to lock a ReentrantLock and also which thread is owning that lock.

In addition, it has a new "detect deadlock" button (in the bottom). When you click on the "detect deadlock" button, it will send a request to the target application to perform the deadlock detection operation. If the target application is running on Mustang, it finds deadlocks involving both object monitors as well as the java.util.concurrent.locks. If the target application is running on Tiger, it finds deadlocks involving object monitors only. Each deadlock cycle will be displayed in a separate Deadlock tab.

Click here to see a wider form of this screenshot.

JDK 6 has a nice demo FullThreadDump under $JDK_HOME/demo/management/FullThreadDump where JDK_HOME is the location of your JDK 6. This demo has been included in JDK 5.0 and is updated to use the new Mustang API. It demonstrates the use of the java.lang.management API to get the thread dump and detect deadlock programmatically.