jstack thread dump error: get_thread_regs failed for a lwp

[Max Lynch]

When using jstack on 9.10 x86_64 (2.6.31-302-rs #7 SMP), with sun-java6-jdk (6.20dlj-0ubuntu1.9.10) it fails with get_thread_regs failed for a lwp errors.

Example:
$ jstack -F 8812

Attaching to process ID 8819, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 16.3-b01
Deadlock Detection:

No deadlocks found.

Thread 8863: (state = BLOCKED)
Error occurred during stack walking:
sun.jvm.hotspot.debugger.DebuggerException: sun.jvm.hotspot.debugger.DebuggerException: get_thread_regs failed for a lwp
        at sun.jvm.hotspot.debugger.linux.LinuxDebuggerLocal$LinuxDebuggerLocalWorkerThread.execute(LinuxDebuggerLocal.java:152)
        at sun.jvm.hotspot.debugger.linux.LinuxDebuggerLocal.getThreadIntegerRegisterSet(LinuxDebuggerLocal.java:466)
        at sun.jvm.hotspot.debugger.linux.LinuxThread.getContext(LinuxThread.java:65)
        at sun.jvm.hotspot.runtime.linux_amd64.LinuxAMD64JavaThreadPDAccess.getCurrentFrameGuess(LinuxAMD64JavaThreadPDAccess.java:92)
        at sun.jvm.hotspot.runtime.JavaThread.getCurrentFrameGuess(JavaThread.java:256)
        at sun.jvm.hotspot.runtime.JavaThread.getLastJavaVFrameDbg(JavaThread.java:218)
        at sun.jvm.hotspot.tools.StackTrace.run(StackTrace.java:76)
        at sun.jvm.hotspot.tools.StackTrace.run(StackTrace.java:45)
        at sun.jvm.hotspot.tools.JStack.run(JStack.java:60)
        at sun.jvm.hotspot.tools.Tool.start(Tool.java:221)
        at sun.jvm.hotspot.tools.JStack.main(JStack.java:86)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)
        at sun.tools.jstack.JStack.runJStackTool(JStack.java:118)
        at sun.tools.jstack.JStack.main(JStack.java:84)
Caused by: sun.jvm.hotspot.debugger.DebuggerException: get_thread_regs failed for a lwp
        at sun.jvm.hotspot.debugger.linux.LinuxDebuggerLocal.getThreadIntegerRegisterSet0(Native Method)
        at sun.jvm.hotspot.debugger.linux.LinuxDebuggerLocal.access$800(LinuxDebuggerLocal.java:51)
        at sun.jvm.hotspot.debugger.linux.LinuxDebuggerLocal$1GetThreadIntegerRegisterSetTask.doit(LinuxDebuggerLocal.java:460)
        at sun.jvm.hotspot.debugger.linux.LinuxDebuggerLocal$LinuxDebuggerLocalWorkerThread.run(LinuxDebuggerLocal.java:127)

AFAIK this is unexpected behavior, and instead a working thread dump should be shown. Unfortunately this is my first experience with jstack so I don't know exactly what I should be seeing.

[Martin Kuen (martin-kuen)]

java version "1.6.0_20"
Java(TM) SE Runtime Environment (build 1.6.0_20-b02)
Java HotSpot(TM) 64-Bit Server VM (build 16.3-b01, mixed mode)

ubuntu 10.04 LTS 64-bit

You must invoke jstack as the user who started/is running the given process.
The above error occurs if you invoke jstack as "root"/via sudo (Has Super Cow Powers but is still the wrong user)

I guess you tried the "-F" option, because it didn't work without it. Therefore, you tried the sledgehammer :). "-F" IS for a hung process.

If you want to create a thread dump of e.g. tomcat6 (installed from ubuntu package repo) you must type the following:

"sudo -u tomcat6 jstack 8812"

Executes jstack as user tomcat6, who is running the service tomcat6, assuming tomcat's pid is 8812.

This is not an ubuntu bug, it's - say - some sort of usability issue with this jstack thing. Blame Sun/Oracle . . .

[Max (ihasmax)]

Thanks for the response.

I was running this as the same user of the process, not as root.

Fortunately (but not for the resolution of this bug) my process is no longer hanging so I can't recreate it. I'll comment again if it happens again.

[Jakub Milkiewicz (jmilkiewicz)]

Hi

I also faced dreadful "get_thread_regs failed for a lwp .." but depending on switches to jstack and whether i run my application in IDE ( eclipse based SpringSource Tools Suite) or from gnome-terminal jstack works..

Below are my observations:
- application ran from IDE, jstack <PID>
in gnome-terminal i got: "Unable to open socket file: target process not responding or HotSpot VM not loaded
The -F option can be used when the target process is not responding"

i can clearly see correct thread dump on eclipse console (sysout)

- application ran from IDE, jstack -F <PID>
in terminal i got: "Attaching to process ID 3744, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 17.0-b16
sun.jvm.hotspot.debugger.DebuggerException: sun.jvm.hotspot.debugger.DebuggerException: get_thread_regs failed for a lwp ..."
on eclipse console (sysout/syserr) i see no stackTrace

- application ran from gnome-terminal, jstack <PID>
in terminal i got correct thread dump. application sysout/syserr is clear

- application ran from gnome-terminal, jstack -F <PID>
in terminal i got "Attaching to process ID 4265, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 17.0-b16
sun.jvm.hotspot.debugger.DebuggerException: sun.jvm.hotspot.debugger.DebuggerException: get_thread_regs failed for a lwp ..."
application sysout/syserr is clear

Ubuntu 10.04.1 LTS

uname -a:
2.6.32-25-generic #44-Ubuntu SMP Fri Sep 17 20:05:27 UTC 2010 x86_64 GNU/Linux

java -version:
java version "1.6.0_21"
Java(TM) SE Runtime Environment (build 1.6.0_21-b06)
Java HotSpot(TM) 64-Bit Server VM (build 17.0-b16, mixed mode)

[Andrew Ball (anball-gmail)]

For Tomcat, I was able to use "kill -3 <tomcat_pid>" as a workaround. I got basically the same behavior with OpenJDK on Ubuntu 10.10 x86_64.

[Nathan Smith (nace)]

I am seeing the exact same behavior on CentOS 5.4 x64, so not necessarily Ubuntu-specific:

# uname -a
Linux ip-#-#-#-# 2.6.21.7-2.fc8xen #1 SMP Fri Feb 15 12:34:28 EST 2008 x86_64 x86_64 x86_64 GNU/Linux

# java -version
Java(TM) SE Runtime Environment (build 1.6.0_14-b08)
Java HotSpot(TM) 64-Bit Server VM (build 14.0-b16, mixed mode)

(server: Jetty 7.4.5)

The "get_thread_regs failed for a lwp" errors occur regardless of whether I invoke jstack as root or as the user that java is running as.

Does anyone have any updates on this? There's not much online about it.