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For example, this is a stack trace from a Tomcat server:
"RMI TCP Accept-0" daemon prio=10 tid=0x091a5800 nid=0x8f1 runnable [0x8b305000] java.lang.Thread.State: RUNNABLE at java.net.PlainSocketImpl.socketAccept(Native Method) at java.net.PlainSocketImpl.accept(PlainSocketImpl.java:408) - locked <0x911d3c30> (a java.net.SocksSocketImpl) at java.net.ServerSocket.implAccept(ServerSocket.java:462) at java.net.ServerSocket.accept(ServerSocket.java:430) at sun.management.jmxremote.LocalRMIServerSocketFactory$1.accept(LocalRMIServerSocketFactory.java:34) at sun.rmi.transport.tcp.TCPTransport$AcceptLoop.executeAcceptLoop(TCPTransport.java:369) at sun.rmi.transport.tcp.TCPTransport$AcceptLoop.run(TCPTransport.java:341) at java.lang.Thread.run(Thread.java:662) My guess is that "locked" means the CPU is waiting on some sort of a lock. However, if that is the case, why is the thread's state listed as RUNNABLE rather than BLOCKED?
Thanks.
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Simply put, a stack trace is a representation of a call stack at a certain point in time, with each element representing a method invocation. The stack trace contains all invocations from the start of a thread until the point it's generated. This is usually a position at which an exception takes place.
To read this stack trace, start at the top with the Exception's type - ArithmeticException and message The denominator must not be zero . This gives an idea of what went wrong, but to discover what code caused the Exception, skip down the stack trace looking for something in the package com.
Just use new Throwable(). printStackTrace() method and it will print complete stack trace from where a method is called, into the console.
Stack trace error is a generic term frequently associated with long error messages. The stack trace information identifies where in the program the error occurs and is helpful to programmers. For users, the long stack track information may not be very useful for troubleshooting web errors.
It means that this thread (RMI TCP Accept-0) has ownership of the object with hash code 0x911d3c30, in this case a java.net.SocksSocketImpl. While this thread owns the lock, no other thread can have it, blocking them from entering this portion of code (often a function). See here for more info:
http://download.oracle.com/javase/tutorial/essential/concurrency/newlocks.html
Also, it is RUNNABLE because it is still running... If you notice that the locked is not at the TOP of the stack but rather inside it, that means that it holds the lock and continued executing. The next thread to come by this section of code would be blocked by that lock.
EDIT Because this is too awkward to fit into a comment... If you see THIS, you are seeing a thread that is blocked. Note is says waiting to lock
"http-80-exec-113": at com.airs.utilities.server.Entity.serializeZip64(Entity.java:6314) - waiting to lock <0x00007fbefe44d5c8> (a java.lang.String) at com.airs.utilities.server.Entity.serializeZip64(Entity.java:6300) If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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