通过jstack分析解决进程死锁问题实例代码

刚才用jstack解决了一个进程死锁的问题——其实早就解决了，也知道原因，只是一直没找到死锁的位置，不太甘心而已。

流程大致如下：

(0)环境要求，jdk1.6及以上

(1)先找到进程的pid，windows下，打开进程管理器，按照名字排序，可以找到叫做javaw.exe的进程(java虚拟机进程一律叫做javaw.exe)，要找出哪个是你的进程，记住当前进程列表，然后重启你的进程，pid刷新过的那个即是你的进程。

(2)在cmd下运行：jstack pid，jstack会在console上打出一系列信息

(3)分析上述信息

实例：

我这个问题的的jstack信息如下：

c:\documents and settings\user>jstack 6652
2012-06-07 21:32:02
full thread dump java hotspot(tm) client vm (16.3-b01 mixed mode, sharing):

"thread-1" daemon prio=6 tid=0x03010c00 nid=0xcdc waiting for monitor entry [0x0
339f000]
  java.lang.thread.state: blocked (on object monitor)
    at org.apache.commons.net.telnet.telnetinputstream.__read(telnetinputstr
eam.java:122)
    - waiting to lock <0x22942280> (a org.apache.commons.net.ftp.ftpclient)
    at org.apache.commons.net.telnet.telnetinputstream.run(telnetinputstream
.java:535)
    at java.lang.thread.run(thread.java:619)

"framework event dispatcher" daemon prio=6 tid=0x03010400 nid=0x998 in object.wa
it() [0x0334f000]
  java.lang.thread.state: waiting (on object monitor)
    at java.lang.object.wait(native method)
    - waiting on <0x228fa800> (a org.eclipse.osgi.framework.eventmgr.eventma
nager$eventthread)
    at java.lang.object.wait(object.java:485)
    at org.eclipse.osgi.framework.eventmgr.eventmanager$eventthread.getnexte
vent(eventmanager.java:400)
    - locked <0x228fa800> (a org.eclipse.osgi.framework.eventmgr.eventmanage
r$eventthread)
    at org.eclipse.osgi.framework.eventmgr.eventmanager$eventthread.run(even
tmanager.java:336)

"start level event dispatcher" daemon prio=6 tid=0x02fcf400 nid=0x2638 in object
.wait() [0x032de000]
  java.lang.thread.state: waiting (on object monitor)
    at java.lang.object.wait(native method)
    - waiting on <0x2295db48> (a [i)
    at java.lang.object.wait(object.java:485)
    at org.apache.commons.net.telnet.telnetinputstream.read(telnetinputstrea
m.java:339)
    - locked <0x2295db48> (a [i)
    at org.apache.commons.net.telnet.telnetinputstream.read(telnetinputstrea
m.java:466)
    at java.io.bufferedinputstream.read1(bufferedinputstream.java:256)
    at java.io.bufferedinputstream.read(bufferedinputstream.java:317)
    - locked <0x2295fe18> (a java.io.bufferedinputstream)
    at sun.nio.cs.streamdecoder.readbytes(streamdecoder.java:264)
    at sun.nio.cs.streamdecoder.implread(streamdecoder.java:306)
    at sun.nio.cs.streamdecoder.read(streamdecoder.java:158)
    - locked <0x22961f88> (a java.io.inputstreamreader)
    at java.io.inputstreamreader.read(inputstreamreader.java:167)
    at java.io.bufferedreader.fill(bufferedreader.java:136)
    at java.io.bufferedreader.readline(bufferedreader.java:299)
    - locked <0x22961f88> (a java.io.inputstreamreader)
    at java.io.bufferedreader.readline(bufferedreader.java:362)
    at org.apache.commons.net.ftp.ftp.__getreply(ftp.java:264)
    at org.apache.commons.net.ftp.ftp._connectaction_(ftp.java:335)
    at org.apache.commons.net.ftp.ftpclient._connectaction_(ftpclient.java:5
50)
    at org.apache.commons.net.socketclient.connect(socketclient.java:163)
    at com.mycompany.dc.ftp.client.ftpclientimpl.connect(ftpclientimpl.java:7
5)
    - locked <0x22942280> (a org.apache.commons.net.ftp.ftpclient)
    at com.mycompany.dc.ftp.client.ftpclientfactoryimpl.getclient(ftpclientfa
ctoryimpl.java:35)
    - locked <0x228f9310> (a java.lang.object)
    at ftpclienttest.activator.start(activator.java:43)
    at org.eclipse.osgi.framework.internal.core.bundlecontextimpl$1.run(bund
lecontextimpl.java:711)
    at java.security.accesscontroller.doprivileged(native method)
    at org.eclipse.osgi.framework.internal.core.bundlecontextimpl.startactiv
ator(bundlecontextimpl.java:702)
    at org.eclipse.osgi.framework.internal.core.bundlecontextimpl.start(bund
lecontextimpl.java:683)
    at org.eclipse.osgi.framework.internal.core.bundlehost.startworker(bundl
ehost.java:381)
    at org.eclipse.osgi.framework.internal.core.abstractbundle.resume(abstra
ctbundle.java:389)
    at org.eclipse.osgi.framework.internal.core.framework.resumebundle(frame
work.java:1131)
    at org.eclipse.osgi.framework.internal.core.startlevelmanager.resumebund
les(startlevelmanager.java:559)
    at org.eclipse.osgi.framework.internal.core.startlevelmanager.resumebund
les(startlevelmanager.java:544)
    at org.eclipse.osgi.framework.internal.core.startlevelmanager.incfwsl(st
artlevelmanager.java:457)
    at org.eclipse.osgi.framework.internal.core.startlevelmanager.dosetstart
level(startlevelmanager.java:243)
    - locked <0x27e68d70> (a java.lang.object)
    at org.eclipse.osgi.framework.internal.core.startlevelmanager.dispatchev
ent(startlevelmanager.java:438)
    at org.eclipse.osgi.framework.internal.core.startlevelmanager.dispatchev
ent(startlevelmanager.java:1)
    at org.eclipse.osgi.framework.eventmgr.eventmanager.dispatchevent(eventm
anager.java:230)
    at org.eclipse.osgi.framework.eventmgr.eventmanager$eventthread.run(even
tmanager.java:340)

"framework active thread" prio=6 tid=0x02ff1800 nid=0x1fbc in object.wait() [0x0
328f000]
  java.lang.thread.state: timed_waiting (on object monitor)
    at java.lang.object.wait(native method)
    - waiting on <0x27e65770> (a org.eclipse.osgi.framework.internal.core.fr
amework)
    at org.eclipse.osgi.framework.internal.core.framework.run(framework.java
:1817)
    - locked <0x27e65770> (a org.eclipse.osgi.framework.internal.core.framew
ork)
    at java.lang.thread.run(thread.java:619)

"osgi console" prio=6 tid=0x03005400 nid=0x225c waiting on condition [0x0323f000
]
  java.lang.thread.state: timed_waiting (sleeping)
    at java.lang.thread.sleep(native method)
    at org.eclipse.osgi.framework.internal.core.frameworkconsole.runconsole(
frameworkconsole.java:125)
    at org.eclipse.osgi.framework.internal.core.frameworkconsole.run(framewo
rkconsole.java:104)
    at java.lang.thread.run(thread.java:619)

"low memory detector" daemon prio=6 tid=0x02c09800 nid=0x1d68 runnable [0x000000
00]
  java.lang.thread.state: runnable

"compilerthread0" daemon prio=10 tid=0x02c03000 nid=0x24c4 waiting on condition
[0x00000000]
  java.lang.thread.state: runnable

"attach listener" daemon prio=10 tid=0x02c01800 nid=0x1138 waiting on condition
[0x00000000]
  java.lang.thread.state: runnable

"signal dispatcher" daemon prio=10 tid=0x02c20c00 nid=0x18ac runnable [0x0000000
0]
  java.lang.thread.state: runnable

"finalizer" daemon prio=8 tid=0x02bc0400 nid=0x11ac in object.wait() [0x02d8f000
]
  java.lang.thread.state: waiting (on object monitor)
    at java.lang.object.wait(native method)
    - waiting on <0x27d5e5c8> (a java.lang.ref.referencequeue$lock)
    at java.lang.ref.referencequeue.remove(referencequeue.java:118)
    - locked <0x27d5e5c8> (a java.lang.ref.referencequeue$lock)
    at java.lang.ref.referencequeue.remove(referencequeue.java:134)
    at java.lang.ref.finalizer$finalizerthread.run(finalizer.java:159)

"reference handler" daemon prio=10 tid=0x02bbb800 nid=0x9cc in object.wait() [0x
02d3f000]
  java.lang.thread.state: waiting (on object monitor)
    at java.lang.object.wait(native method)
    - waiting on <0x27d5e650> (a java.lang.ref.reference$lock)
    at java.lang.object.wait(object.java:485)
    at java.lang.ref.reference$referencehandler.run(reference.java:116)
    - locked <0x27d5e650> (a java.lang.ref.reference$lock)

"main" prio=6 tid=0x008a6c00 nid=0x22ec in object.wait() [0x0098f000]
  java.lang.thread.state: timed_waiting (on object monitor)
    at java.lang.object.wait(native method)
    - waiting on <0x22c303c8> (a org.eclipse.core.runtime.internal.adaptor.s
emaphore)
    at org.eclipse.core.runtime.internal.adaptor.semaphore.acquire(semaphore
.java:55)
    - locked <0x22c303c8> (a org.eclipse.core.runtime.internal.adaptor.semap
hore)
    at org.eclipse.core.runtime.adaptor.eclipsestarter.updatesplash(eclipses
tarter.java:1251)
    at org.eclipse.core.runtime.adaptor.eclipsestarter.setstartlevel(eclipse
starter.java:1213)
    at org.eclipse.core.runtime.adaptor.eclipsestarter.startup(eclipsestarte
r.java:288)
    at org.eclipse.core.runtime.adaptor.eclipsestarter.run(eclipsestarter.ja
va:175)
    at sun.reflect.nativemethodaccessorimpl.invoke0(native method)
    at sun.reflect.nativemethodaccessorimpl.invoke(nativemethodaccessorimpl.
java:39)
    at sun.reflect.delegatingmethodaccessorimpl.invoke(delegatingmethodacces
sorimpl.java:25)
    at java.lang.reflect.method.invoke(method.java:597)
    at org.eclipse.equinox.launcher.main.invokeframework(main.java:622)
    at org.eclipse.equinox.launcher.main.basicrun(main.java:577)
    at org.eclipse.equinox.launcher.main.run(main.java:1410)
    at org.eclipse.equinox.launcher.main.main(main.java:1386)

"vm thread" prio=10 tid=0x02bba000 nid=0xdb4 runnable

"vm periodic task thread" prio=10 tid=0x02c0e400 nid=0x24ac waiting on condition

jni global references: 677

分析：

根据提示，有两个线程都用到了ftpclient这个对象作为锁，而且前一个得到锁的要等待后一个需要这个锁的返回结果，造成死锁。这两处分别为：

(1) at org.apache.commons.net.telnet.telnetinputstream.__read(telnetinputstr

eam.java:122)

(2) - locked <0x22942280> (a org.apache.commons.net.ftp.ftpclient)

at com.sagemcom.dc.ftp.client.ftpclientfactoryimpl.getclient(ftpclientfa

ctoryimpl.java:35)

- locked <0x228f9310> (a java.lang.object)

前者是系统自己用的锁，后者是我代码里面加的。自己代码里面换一个对象做锁就解决了。

总结

jstack在解决问题上还是比较有帮助的，信息简洁有效，其实有很多图形化的分析工具是基于它的。但jstack需要jdk1.6以上的版本才支持。

以上就是本文关于通过jstack分析解决进程死锁问题实例代码的全部内容，希望对大家有所帮助。感兴趣的朋友可以继续参阅本站其他相关专题，如有不足之处，欢迎留言指出。感谢朋友们对本站的支持！