RFR: 8192897: NPE occurs on clhsdb jstack

[Sharath Ballal]

Hi Yasumasa,
I tried jhsdb with a simple HelloWorld (with -Xcomp) and did not see any exception.
Your app does anything else ?

Thanks,
Sharath


-----Original Message-----
From: Yasumasa Suenaga [mailto:yasuenag at gmail.com] 
Sent: Friday, December 01, 2017 7:26 PM
To: serviceability-dev at openjdk.java.net
Subject: RFR: 8192897: NPE occurs on clhsdb jstack

Hi all,

I saw NPE when I run jstack on clhsdb as below:

----------------
hsdb> jstack
Deadlock Detection:

No deadlocks found.

"NonBlockingInputStreamThread" #27 daemon prio=5 tid=0x00007f0924674000 nid=0xf429 in Object.wait() [0x00007f08cf6fd000]
    java.lang.Thread.State: WAITING (on object monitor)
    JavaThread state: _thread_blocked
  - java.lang.Object.wait(long) @bci=0 (Compiled frame; information may be imprecise)
         - waiting on <no object reference available> Error occurred during stack walking:
java.lang.NullPointerException
         at jdk.hotspot.agent/sun.jvm.hotspot.runtime.CompiledVFrame.getMonitors(CompiledVFrame.java:131)
         at jdk.hotspot.agent/sun.jvm.hotspot.runtime.JavaVFrame.printLockInfo(JavaVFrame.java:125)
         at jdk.hotspot.agent/sun.jvm.hotspot.tools.StackTrace.run(StackTrace.java:114)
         at jdk.hotspot.agent/sun.jvm.hotspot.CommandProcessor$26.doit(CommandProcessor.java:1073)
         at jdk.hotspot.agent/sun.jvm.hotspot.CommandProcessor.executeCommand(CommandProcessor.java:1964)
         at jdk.hotspot.agent/sun.jvm.hotspot.CommandProcessor.executeCommand(CommandProcessor.java:1934)
         at jdk.hotspot.agent/sun.jvm.hotspot.CommandProcessor.run(CommandProcessor.java:1814)
         at jdk.hotspot.agent/sun.jvm.hotspot.CLHSDB.run(CLHSDB.java:99)
         at jdk.hotspot.agent/sun.jvm.hotspot.CLHSDB.main(CLHSDB.java:40)
         at jdk.hotspot.agent/sun.jvm.hotspot.SALauncher.runCLHSDB(SALauncher.java:191)
         at jdk.hotspot.agent/sun.jvm.hotspot.SALauncher.main(SALauncher.java:439)
----------------

It is caused by CompiledVFrame#getScope() returns null.
We should consider it at CompiledVFrame#getMonitors().

I uploaded a webrev. Could you review it?
I checked this change with hotspot/jtreg/serviceability/sa on Linux x64.

   http://cr.openjdk.java.net/~ysuenaga/JDK-8192897/webrev.00/

We can reproduce this issue when we run the app with -Xcomp option.
So I changed ClhsdbJstack.java to run with it.


I cannot access mach5 and JPRT. So I need sponsor.


Thanks,

Yasumasa