JDK-8293156: Dcmd VM.classloaders fails to print the full hierarchy by tstuefe · Pull Request #10312 · openjdk/jdk

tstuefe · 2022-09-16T14:55:42Z

Fixes a bug in the VM.classloaders jcmd that causes class loaders to be omitted from the output if a parent class loader never loaded any class and therefore had no associated DCmd.

The fix changes the command to not rely on the existence of a CLD structure for the loader; instead, all information (loader class name, loader name, etc) is pulled via the loader oop, which has to be always there unless its the bootstrap loader.

Also, the tests were expanded to test the display of empty loaders and empty parent loaders.

Thanks to @dholmes-ora for finding this bug.

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Issue

JDK-8293156: Dcmd VM.classloaders fails to print the full hierarchy

Reviewers

David Holmes (@dholmes-ora - Reviewer)
Chris Plummer (@plummercj - Reviewer)

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bridgekeeper · 2022-09-16T14:55:46Z

👋 Welcome back stuefe! 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.

openjdk · 2022-09-16T14:57:51Z

@tstuefe The following labels will be automatically applied to this pull request:

hotspot-runtime
serviceability

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

mlbridge · 2022-09-16T15:06:10Z

Webrevs

src/hotspot/share/classfile/classLoaderHierarchyDCmd.cpp

plummercj · 2022-09-19T18:48:18Z

src/hotspot/share/classfile/classLoaderHierarchyDCmd.cpp

+    return (loader_klass() != NULL) && (loader_klass() == target_node->loader_klass()) &&
+           ((loader_name_oop() == NULL && target_node->loader_name_oop() == NULL) ||
+             (::strcmp(loader_name(), target_node->loader_name()) == 0));


This is hard to parse. I think using if/else statements would be cleaner.

test/hotspot/jtreg/serviceability/dcmd/vm/ClassLoaderHierarchyTest.java

tstuefe · 2022-09-20T05:33:10Z

Hi @plummercj , thanks for your Review. I worked most of your your feedback.

.. Thomas

dholmes-ora

Hi Thomas,

Generally this seems fine - but one issue below.

Thanks.

dholmes-ora · 2022-09-21T02:26:02Z

src/hotspot/share/classfile/classLoaderHierarchyDCmd.cpp

+        st->print(" \"%s\",", the_loader_name);
      }
-      st->print(" %s", loader_klass != NULL ? loader_klass->external_name() : "??");
+      st->print(" %s", the_loader_class_name);


the_loader_class_name could be NULL here. You need to change loader_class_name() t return "??" like the original code uses.

Good catch. We never encounter this because Klass can only be null for the bootstrap loader, which is handled in a different branch. I'll fix it.

tstuefe · 2022-09-21T06:46:18Z

Hi @plummercj , thanks for your Review. I worked most of your your feedback.

.. Thomas

tstuefe · 2022-09-21T06:47:52Z

Fixed all remaining occurrences of "childs"
Fixed possible segfault when printing class name for bootstrap loader
Fixed GHAs (apparently we don't have a MainWrapper class when executing jtreg in GHAs, so I cannot parse for it)

dholmes-ora

Nothing further from me. Thanks!

openjdk · 2022-09-21T07:45:44Z

@tstuefe 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:

8293156: Dcmd VM.classloaders fails to print the full hierarchy

Reviewed-by: dholmes, cjplummer

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 91 new commits pushed to the master branch:

e195897: 8294068: Unconditional and eager load of nio library since JDK-8264744
84d7ff6: 8288129: Shenandoah: Skynet test crashed with iu + aggressive
07afa3f: 8294110: compiler/uncommontrap/Decompile.java fails after JDK-8293798
0746bcb: 8294083: RISC-V: Minimal build failed with --disable-precompiled-headers
95ec2ea: 8293897: Synthetic final modifier is part of the AST for a try-with-resource resource
d14e96d: 8293493: Signal Handlers printout should show signal block state
da4fdfb: 8293659: Improve UnsatisfiedLinkError error message to include dlopen error details
cd1cdcd: 8293116: Incremental JDK build could be sped up
e9401e6: 8293364: IGV: Refactor Action in EditorTopComponent and fix minor bugs
844a95b: 8292892: Javadoc index descriptions are not deterministic
... and 81 more: https://git.openjdk.org/jdk/compare/7f3250d71c4866a64eb73f52140c669fe90f122f...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.

tstuefe · 2022-09-21T17:05:51Z

Thanks @plummercj and @dholmes-ora .

/integrate

openjdk · 2022-09-21T17:07:54Z

Going to push as commit c6be2cd.
Since your change was applied there have been 93 commits pushed to the master branch:

711e252: 8294039: Remove "Classpath" exception from java/awt tests
27b8e2f: 8294038: Remove "Classpath" exception from javax/swing tests
e195897: 8294068: Unconditional and eager load of nio library since JDK-8264744
84d7ff6: 8288129: Shenandoah: Skynet test crashed with iu + aggressive
07afa3f: 8294110: compiler/uncommontrap/Decompile.java fails after JDK-8293798
0746bcb: 8294083: RISC-V: Minimal build failed with --disable-precompiled-headers
95ec2ea: 8293897: Synthetic final modifier is part of the AST for a try-with-resource resource
d14e96d: 8293493: Signal Handlers printout should show signal block state
da4fdfb: 8293659: Improve UnsatisfiedLinkError error message to include dlopen error details
cd1cdcd: 8293116: Incremental JDK build could be sped up
... and 83 more: https://git.openjdk.org/jdk/compare/7f3250d71c4866a64eb73f52140c669fe90f122f...master

Your commit was automatically rebased without conflicts.

openjdk · 2022-09-21T17:08:21Z

@tstuefe Pushed as commit c6be2cd.

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

JDK-8293156-Dcmd-VM.classloaders-fails-to-print-the-full-hierarchy

0f5de19

openjdk bot added serviceability serviceability-dev@openjdk.org hotspot-runtime hotspot-runtime-dev@openjdk.org labels Sep 16, 2022

tstuefe marked this pull request as ready for review September 16, 2022 14:59

openjdk bot added the rfr Pull request is ready for review label Sep 16, 2022

plummercj reviewed Sep 19, 2022

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cjplummer feedback

224df5f

dholmes-ora suggested changes Sep 21, 2022

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tstuefe added 3 commits September 21, 2022 08:36

childs->children

4029ddc

feedback dholmes

992f829

Fix test error in GHAs

3510ddc

tstuefe closed this Sep 21, 2022

tstuefe reopened this Sep 21, 2022

dholmes-ora approved these changes Sep 21, 2022

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openjdk bot added the ready Pull request is ready to be integrated label Sep 21, 2022

plummercj approved these changes Sep 21, 2022

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openjdk bot added the integrated Pull request has been integrated label Sep 21, 2022

openjdk bot closed this Sep 21, 2022

openjdk bot removed ready Pull request is ready to be integrated rfr Pull request is ready for review labels Sep 21, 2022

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