Ok. Have you found a way to test your changes? Maybe just force or
simulate a failure somehow.
Chris
On 9/5/18 11:26 AM, Gary Adams wrote:
If we go ahead with this proposed fix, the next time it fails
we will have more information about the other threads
captured in the log.
One last observation, the test that failed was running with UseZGC.
Not sure how that might impact this particular test.
On 9/5/18, 2:07 PM, Chris Plummer wrote:
Hi Gary,
If the DebugThreadTarg is resumed prematurely,
The failure explanation seems to hinge on this, but I don't see how
this can happen. What is resuming DebugThreadTarg? Only the call to
listenUntilVMDisconnect() should be doing this, and we aren't even
getting that far. The only thing I can think of is due to some other
issue (maybe host out of memory so process was killed off), the
DebugThreadTarg process has exited unexpectedly. In this case I guess
the fix you have is appropriate defensive programming, causing the
test to fail when this happens, but still won't explain why it
happens and also won't prevent future failures of this test. Also,
this type of Debuggee early exit problem could happen with other
tests too. I'm leaning towards just closing this bug as CNR. I don't
think we want to be writing our tests to defend against random system
related failures, especially when the end result is still going to be
a test failure that we don't fully understand.
thanks,
Chris
On 9/5/18 7:33 AM, Gary Adams wrote:
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 +
