8290200: com/sun/jdi/InvokeHangTest.java fails with "Debuggee appears to be hung" #13068

plummercj · 2023-03-16T21:02:09Z

The debuggee main method creates two threads and then starts them:

    public static void main(String[] args) {
        System.out.println("Howdy!");
        Thread t1 = TestScaffold.newThread(new InvokeHangTarg(), name1);
        Thread t2 = TestScaffold.newThread(new InvokeHangTarg(), name2);

        t1.start();
        t2.start();
    }

These threads will hit breakpoints which the debugger handles and issues an invoke on the breakpoint thread. The threads run until they generate 100 breakpoints. There is an issue when these two threads are virtual threads. Virtual threads are daemon threads. That means the JVM can exit while they are still running. The above main() method is not waiting for these two threads to exit, so main() exits immediately and the JVM starts the shutdown process. It first must wait for all non-daemon threads to exit, but there are none, so the JVM exits right away before the two threads are completed. The end result of this early exit is that sometimes the invoke done by the debugger never completes because the JVM has already issued a VMDeath event and the debuggee has been disconnected.

When these two threads are platform threads, the JVM has to wait until they complete before it exits, so they will always complete. The fix for virtual threads is to do a join with t1 and t2. This forces the main() method to block until they have completed.

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Issue

JDK-8290200: com/sun/jdi/InvokeHangTest.java fails with "Debuggee appears to be hung"

Reviewers

Alex Menkov (@alexmenkov - Reviewer) ⚠️ Review applies to 4d28b92e
Leonid Mesnik (@lmesnik - Reviewer) ⚠️ Review applies to 4d28b92e
Serguei Spitsyn (@sspitsyn - Reviewer) ⚠️ Review applies to 4d28b92e
Daniel D. Daugherty (@dcubed-ojdk - Reviewer) ⚠️ Review applies to 58ca27b8

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$ git checkout pull/13068

Update a local copy of the PR:
$ git checkout pull/13068
$ git pull https://git.openjdk.org/jdk pull/13068/head

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Checkout this PR locally:
$ git pr checkout 13068

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https://git.openjdk.org/jdk/pull/13068.diff

… complete.

bridgekeeper · 2023-03-16T21:03:32Z

👋 Welcome back cjplummer! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

plummercj · 2023-03-16T21:04:34Z

test/jdk/com/sun/jdi/InvokeHangTest.java

@@ -214,7 +220,7 @@ protected void runTests() throws Exception {
        targetClass = bpe.location().declaringType();
        mainThread = bpe.thread();
        EventRequestManager erm = vm().eventRequestManager();
-        final Thread mainThread = Thread.currentThread();
+        final Thread mainTestThread = Thread.currentThread();


This local variable was conflicting with an instance field of the same name. See line 135. I ran into issues when I added some debugging code to this method that referenced the other mainThread, so I did a rename.

openjdk · 2023-03-16T21:06:43Z

@plummercj The following label will be automatically applied to this pull request:

serviceability

When this pull request is ready to be reviewed, an "RFR" email will be sent to the corresponding mailing list. If you would like to change these labels, use the /label pull request command.

mlbridge · 2023-03-16T21:10:49Z

Webrevs

alexmenkov · 2023-03-16T21:25:47Z

test/jdk/com/sun/jdi/InvokeHangTest.java

@@ -191,7 +197,7 @@ public void breakpointReached(BreakpointEvent event) {
        ThreadReference thread = event.thread();
        try {
            StackFrame sf = thread.frame(0);
-            System.err.println("  Debugger: Breakpoint hit at "+sf.location());
+            System.out.println("  Debugger: Breakpoint hit at "+sf.location());


while you are here please add spaces around plus

openjdk · 2023-03-16T21:26:55Z

@plummercj This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

8290200: com/sun/jdi/InvokeHangTest.java fails with "Debuggee appears to be hung"

Reviewed-by: amenkov, lmesnik, sspitsyn, dcubed

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 69 new commits pushed to the master branch:

f8482c2: 8297638: Memory leak in case of many started-dead threads
c56f011: 8298995: tools/jpackage/share/AddLauncherTest.java#id1 failed "AddLauncherTest.test; checks=53"
254288a: 8014021: TreeMaker.Params behaves inconsistently when the owning method has the same number of parameters as the number of parameter types requested
8f5bb53: 8015831: Add lint check for calling overridable methods from a constructor
b085ab9: 8180387: com.sun.source.util.JavacTask should have a protected constructor.
bfb812a: 8292818: replace 96-bit representation for field metadata with variable-sized streams
932be35: 8298469: Obsolete legacy parallel class loading workaround for non-parallel-capable class loaders
02a4ee2: 8303921: serviceability/sa/UniqueVtableTest.java timed out
4486f1b: 8304367: jlink --include-locales=* attempts to parse non .class resource files with classfile reader
8d2ebf2: 8303697: ProcessTools doesn't print last line of process output
... and 59 more: https://git.openjdk.org/jdk/compare/7bbc5e0efbcbf97e8c1d4e889bd06c33c5f4eaa5...master

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

➡️ To integrate this PR with the above commit message to the master branch, type /integrate in a new comment.

sspitsyn

Looks good.
Thanks,
Serguei

dcubed-ojdk · 2023-03-17T15:15:16Z

test/jdk/com/sun/jdi/InvokeHangTest.java

+        try {
+            t1.join();
+            t2.join();
+        } catch (InterruptedException e) {
+            throw new RuntimeException(e);
+        }


Please consider adding a comment that explains that the join() calls
are only necessary when t1 and t2 are virtual threads.

dcubed-ojdk

Thumbs up. Thanks for adding the comment.
One possible nit typo...

dcubed-ojdk · 2023-03-18T00:38:01Z

test/jdk/com/sun/jdi/InvokeHangTest.java

+
+        try {
+            // The join ensures that the test completes before we exit main(). If we are using
+            // virtual threads, they are always daemon threads, and therefor the JVM will exit


nit typo: s/therefor/therefore/

plummercj · 2023-03-21T17:59:21Z

/integrate

openjdk · 2023-03-21T18:00:46Z

Going to push as commit 0deb648.
Since your change was applied there have been 98 commits pushed to the master branch:

019fcd8: 8304139: Add and method constants to ConstantDescs
d6f20e2: 8304680: Problemlist compiler/sharedstubs/SharedStubToInterpTest.java
d788a1b: 8304180: Constant Descriptors for MethodHandles::classData and classDataAt
bbde215: 8299494: Test vmTestbase/nsk/stress/except/except011.java failed: ExceptionInInitializerError: target class not found
1c04686: 8304387: Fix positions of shared static stubs / trampolines
c65bb2c: 8304334: java/awt/color/ICC_ColorSpace/ToFromCIEXYZRoundTrip.java times out on slow platforms
4bf1fbb: 8303648: Add String.indexOf(String str, int beginIndex, int endIndex)
c4df9b5: 8304537: Ant-based langtools build fails after JDK-8015831 Add lint check for calling overridable methods from a constructor
a6b72f5: 8304230: LShift ideal transform assertion
a72ba38: 8303948: HsErrFileUtils.checkHsErrFileContent() fails to check the last pattern.
... and 88 more: https://git.openjdk.org/jdk/compare/7bbc5e0efbcbf97e8c1d4e889bd06c33c5f4eaa5...master

Your commit was automatically rebased without conflicts.

openjdk · 2023-03-21T18:01:04Z

@plummercj Pushed as commit 0deb648.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

Make sure main() debuggee method does not exit until test threads are…

4d28b92

… complete.

plummercj commented Mar 16, 2023

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openjdk bot changed the title ~~8290200~~ 8290200: com/sun/jdi/InvokeHangTest.java fails with "Debuggee appears to be hung" Mar 16, 2023

openjdk bot added the rfr Pull request is ready for review label Mar 16, 2023

openjdk bot added the serviceability serviceability-dev@openjdk.org label Mar 16, 2023

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minor formatting fix

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dcubed-ojdk approved these changes Mar 17, 2023

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plummercj added 2 commits March 17, 2023 17:30

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8290200: com/sun/jdi/InvokeHangTest.java fails with "Debuggee appears to be hung" #13068

8290200: com/sun/jdi/InvokeHangTest.java fails with "Debuggee appears to be hung" #13068

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8290200: com/sun/jdi/InvokeHangTest.java fails with "Debuggee appears to be hung" #13068

8290200: com/sun/jdi/InvokeHangTest.java fails with "Debuggee appears to be hung" #13068

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