linux下使用jstack报错，牛人速来支援

jstack -F 20940

Attaching to process ID 20940, please wait...
 sun.jvm.hotspot.debugger.NoSuchSymbolException: Could not find symbol "gHotSpotVMTypes" in any of the known library names (libjvm.so, libjvm_g.so, gamma_g)
 at sun.jvm.hotspot.HotSpotTypeDataBase.lookupInProcess(HotSpotTypeDataBase.java:585)
 at sun.jvm.hotspot.HotSpotTypeDataBase.readVMTypes(HotSpotTypeDataBase.java:150)
 at sun.jvm.hotspot.HotSpotTypeDataBase.(HotSpotTypeDataBase.java:85)
 at sun.jvm.hotspot.bugspot.BugSpotAgent.setupVM(BugSpotAgent.java:569)
 at sun.jvm.hotspot.bugspot.BugSpotAgent.go(BugSpotAgent.java:493)
 at sun.jvm.hotspot.bugspot.BugSpotAgent.attach(BugSpotAgent.java:331)
 at sun.jvm.hotspot.tools.Tool.start(Tool.java:163)
 at sun.jvm.hotspot.tools.JStack.main(JStack.java:86)
 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
 at java.lang.reflect.Method.invoke(Method.java:601)
 at sun.tools.jstack.JStack.runJStackTool(JStack.java:136)
 at sun.tools.jstack.JStack.main(JStack.java:102)
 Debugger attached successfully.
 jstack requires a java VM process/core!