RFR: JDK-8210252: com/sun/jdi/DebuggerThreadTest.java fails with NPE
Gary Adams
gary.adams at oracle.com
Wed Sep 5 14:33:13 UTC 2018
The DebuggerThreadTest ensures it is in sync
at the beginning of RunTests with a breakpoint event
in DebuggerThreadTarg ready() method.
The DebuggerThreadTest then continues with
dumpThreads() and listenUntilVMDisconnect()
completes.
If the DebugThreadTarg is resumed prematurely,
the main thread in the debuggee could complete
before the dumpThreads enumeration is complete.
DebuggerThreadTest
main()
startTests()
runTests()
startTo( "DebuggerThreadTarg.ready()")
dumpThreads()
listenUntilVMDisconnect()
DebuggerThreadTarg
main()
ready()
Revised fix:
- Prevents the NPE from a finished thread group
- Fails the test with a message indicating
number of premature completed threads.
diff --git a/test/jdk/com/sun/jdi/DebuggerThreadTest.java
b/test/jdk/com/sun/jdi/DebuggerThreadTest.java
--- a/test/jdk/com/sun/jdi/DebuggerThreadTest.java
+++ b/test/jdk/com/sun/jdi/DebuggerThreadTest.java
@@ -1,5 +1,5 @@
/*
- * Copyright (c) 2001, 2015, Oracle and/or its affiliates. All rights
reserved.
+ * Copyright (c) 2001, 2018, Oracle and/or its affiliates. All rights
reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
@@ -76,8 +76,16 @@
Thread list[] = new Thread[listThreads * 2];
int gotThreads = tg.enumerate(list, true);
for (int i = 0; i < Math.min(gotThreads, list.length); i++){
+ int finishedThreads = 0;
Thread t = list[i];
- String groupName = t.getThreadGroup().getName();
+ ThreadGroup tga = t.getThreadGroup();
+ String groupName;
+ if (tga == null) {
+ groupName = "<completed>";
+ finishedThreads++ ;
+ } else {
+ groupName =tga.getName();
+ }
System.out.println("Thread [" + i + "] group = '" +
groupName +
@@ -89,7 +97,10 @@
failure("FAIL: non-daemon thread '" + t.getName() +
"' found in ThreadGroup '" + groupName + "'");
}
-
+ if (finishedThreads > 0 ) {
+ failure("FAIL: " + finishedThreads +
+ " threads completed while VM suspended.");
+ }
}
}
On 9/4/18, 3:15 PM, Chris Plummer wrote:
> Hi Gary,
>
> The failed case only had:
>
> Thread [0] group = 'system' name = 'Reference Handler' daemon = true
> Thread [1] group = 'system' name = 'Finalizer' daemon = true
> Thread [2] group = 'system' name = 'Signal Dispatcher' daemon = true
> Thread [3] group = 'system' name = 'process reaper' daemon = true
>
> That would indicate that 'main' is likely the thread that exited.
> Seems odd. Isn't that the thread that the test is executing in?
>
> If you can't reproduce it, maybe it would be better to commit a
> diagnostic fix like the one I suggested and keep an eye on it.
> However, it only seems to have failed once due to this reason, so
> unless it is a new problem we may never see it again.
>
> Chris
>
> On 9/4/18 11:28 AM, Gary Adams wrote:
>> I haven't been able to reproduce the problem locally.
>> Trying larger test runs on mach5 now.
>>
>> Here's the output from a successful test run.
>> If any of the threads exited, they would have a null group name.
>>
>> Howdy!
>> Thread [0] group = 'system' name = 'Reference Handler' daemon = true
>> Thread [1] group = 'system' name = 'Finalizer' daemon = true
>> Thread [2] group = 'system' name = 'Signal Dispatcher' daemon = true
>> Thread [3] group = 'system' name = 'process reaper' daemon = true
>> Thread [4] group = 'main' name = 'main' daemon = false
>> Thread [5] group = 'main' name = 'pool-1-thread-1' daemon = true
>> Thread [6] group = 'AgentVMThreadGroup' name = 'AgentVMThread' daemon
>> = false
>> Thread [7] group = 'AgentVMThreadGroup' name = 'output reader' daemon
>> = false
>> Thread [8] group = 'AgentVMThreadGroup' name = 'output reader' daemon
>> = false
>> Thread [9] group = 'AgentVMThreadGroup' name = 'Thread-5' daemon = true
>> Thread [10] group = 'InnocuousThreadGroup' name = 'Common-Cleaner'
>> daemon = true
>> Thread [11] group = 'JDI [1485331767]' name = 'JDI Internal Event
>> Handler' daemon = true
>> Thread [12] group = 'JDI [1485331767]' name = 'JDI Target VM
>> Interface' daemon = true
>> Goodbye from DebuggerThreadTarg!
>>
>>
>> On 9/4/18, 2:16 PM, Chris Plummer wrote:
>>> Can you reproduce the problem? If so, maybe to find out which thread
>>> is a problem you could check for null, print the thread info, and
>>> then fail the test.
>>>
>>> Chris
>>>
>>> On 9/4/18 11:14 AM, Gary Adams wrote:
>>>> I'm not sure which thread exited causes the NPE.
>>>> This patch will let the test continue and at least
>>>> let the list of threads be processed.
>>>>
>>>> The test walks up the parents to the initial thread
>>>> and then "enumerates()" the set of the threads to check.
>>>> There is an inherent race condition in enumerate()
>>>> that recognizes it is a snapshot of a moving target.
>>>>
>>>> On 9/4/18, 1:51 PM, Chris Plummer wrote:
>>>>> Hi Gary,
>>>>>
>>>>> Why has the thread exited if the debuggee is still running?
>>>>>
>>>>> Chris
>>>>>
>>>>> On 9/4/18 5:22 AM, Gary Adams wrote:
>>>>>> Here's a quick fix to avoid the NPE using a getThreadGroup()
>>>>>> which could be null
>>>>>> if the thread has terminated.
>>>>>>
>>>>>> Issue: https://bugs.openjdk.java.net/browse/JDK-8210252
>>>>>>
>>>>>> diff --git a/test/jdk/com/sun/jdi/DebuggerThreadTest.java
>>>>>> b/test/jdk/com/sun/jdi/DebuggerThreadTest.java
>>>>>> --- a/test/jdk/com/sun/jdi/DebuggerThreadTest.java
>>>>>> +++ b/test/jdk/com/sun/jdi/DebuggerThreadTest.java
>>>>>> @@ -77,7 +77,8 @@
>>>>>> int gotThreads = tg.enumerate(list, true);
>>>>>> for (int i = 0; i < Math.min(gotThreads, list.length);
>>>>>> i++){
>>>>>> Thread t = list[i];
>>>>>> - String groupName = t.getThreadGroup().getName();
>>>>>> + ThreadGroup tga = t.getThreadGroup();
>>>>>> + String groupName = (tga == null ? "<completed>": tga.getName());
>>>>>>
>>>>>> System.out.println("Thread [" + i + "] group = '" +
>>>>>> groupName +
>>>>>
>>>>>
>>>>
>>>
>>>
>>
>
>
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