8261154: Memory leak in Java_java_lang_ClassLoader_defineClass0 with long class names

[cl4es]

This patch resolves a potential memory leak in Java_java_lang_ClassLoader_defineClass0

I've not figured a good way to write a regression test. A crude way to manually verify the leak and the fix is provided by the added microbenchmark that triggers the malloc in ClassLoader.c and the associated leak.

E.g., running this with /usr/bin/time -v $BUILD_DIR/images/jdk/bin/java -Xmx256m -jar $BUILD_DIR/images/test/micro/benchmarks.jar LookupDef.*WeakClass.loadLong -f 0 -i N | grep "Maximum resident set" yields:

Baseline:
N = 20     Maximum resident set size (kbytes): 544860
N = 50     Maximum resident set size (kbytes): 818532
N = 100    Maximum resident set size (kbytes): 1388560
N = 200    Maximum resident set size (kbytes): 2124296
Patch:
N = 20     Maximum resident set size (kbytes): 480476
N = 50     Maximum resident set size (kbytes): 764040
N = 100    Maximum resident set size (kbytes): 782920
N = 200    Maximum resident set size (kbytes): 921272

---

Progress

• Change must not contain extraneous whitespace
• Commit message must refer to an issue
• Change must be properly reviewed

Issue

• JDK-8261154: Memory leak in Java_java_lang_ClassLoader_defineClass0 with long class names

Reviewers

• Thomas Stuefe (@tstuefe - Reviewer)
• Chris Hegarty (@ChrisHegarty - Reviewer)
• Mandy Chung (@mlchung - Reviewer)

Download

$ git fetch https://git.openjdk.java.net/jdk pull/2407/head:pull/2407
$ git checkout pull/2407

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[openjdk]

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[mlbridge]

Webrevs

• 01: Full - Incremental (f25b5f9)
• 00: Full (972696e)

[tstuefe]

Hi Cleas,

looks good but why changing the the NULL comparisons?

If you wanted to simplify you could completely omit the NULL checks since free(NULL) is a noop. And potentially merge the labels - where there are two - into one.

Cheers, Thomas

[cl4es]

I'm not sure every platform have always agreed free(NULL) is a noop. I suspect all the currently supported ones do, though?

[tstuefe]

I'm not sure every platform have always agreed free(NULL) is a noop. I suspect all the currently supported ones do, though?

Its standard behavior.

Posix: https://pubs.opengroup.org/onlinepubs/009695399/functions/free.html "If ptr is a null pointer, no action shall occur. "
Windows: https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/free?view=msvc-160 " If memblock is NULL, the pointer is ignored and free immediately returns. "

So it should be okay.

[cl4es]

Right. I dialed back the changes here since this is a bug fix that should be kept minimal. I have another change in the pipeline that will touch code here that can double down on cleaning up.

[ChrisHegarty]

LGTM.

[tstuefe]

Looks good!

[openjdk]

@cl4es 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:

8261154: Memory leak in Java_java_lang_ClassLoader_defineClass0 with long class names

Reviewed-by: stuefe, chegar, mchung

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 55 new commits pushed to the master branch:

• e93e1e1: 8261157: Incorrect GPL header after JDK-8259956
• c1dea39: 8260335: [macos] Running app using relative path causes problems
• f7a6cff: 8261149: Initial nroff manpage update for JDK 17
• be772ff: 8261023: Document why memory pretouch must be a store
• 83357b1: 8261030: Avoid loading GenerateJLIClassesHelper at runtime
• 992b500: 8261036: Reduce classes loaded by CleanerFactory initialization
• e8ad8b3: 8259956: jdk.jfr.internal.ChunkInputStream#available should return the sum of remaining available bytes
• 06b33a0: 8261107: ArrayIndexOutOfBoundsException in the ICC_Profile.getInstance(InputStream)
• 60f440d: 6436374: Graphics.setColor(null) is not documented
• 82028e7: 8260012: Reduce inclusion of collectedHeap.hpp and heapInspection.hpp
• ... and 45 more: https://git.openjdk.java.net/jdk/compare/ddd2951ba91fe3860b92d2f9bad4e0d900f1d650...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.

[mlchung]

Looks good. Thanks for fixing this.

[cl4es]

@tstuefe, @ChrisHegarty, @mlchung - thanks for reviewing!

/integrate

[openjdk]

@cl4es Since your change was applied there have been 65 commits pushed to the master branch:

• 78b0d32: 8234534: Simplify CardTable code after CMS removal
• ee2f205: 8260926: Trace resource exhausted events unconditionally
• 1e0a101: 8259862: MutableSpace's end should be atomic
• d2bd499: 8163498: Many long-running security libs tests
• c5bb109: 8260019: Move some Thread subtypes out of thread.hpp
• 08f7454: 8261190: restore original Alibaba copyright line in two files
• 3bb6a3d: 8261109: [macOS] Remove disabled warning for JNF in make/autoconf/flags-cflags.m4
• c59e4b6: 8261106: Reduce inclusion of jniHandles.hpp
• d9aefa3: 8260356: (tz) Upgrade time-zone data to tzdata2021a
• bdcbfa1: 8259927: Windows jpackage installer issues
• ... and 55 more: https://git.openjdk.java.net/jdk/compare/ddd2951ba91fe3860b92d2f9bad4e0d900f1d650...master

Your commit was automatically rebased without conflicts.

Pushed as commit 0791899.

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