8298524: Debug function to trace reachability of CDS archived heap objects

[iklam]

Please review this small change to help debugging the CDS heap archiving code.

Here's an example in gdb that shows how the java.lang.Module object at 0x00000005ce8d9ba0 is reached from the root (ArchivedClassLoaders::servicesCatalogs )

Thread 8 "VM Thread" hit Breakpoint 2, HeapShared::check_module_oop (orig_module_obj=0x5ce8bf588)
    at heapShared.cpp:1193
1193	  assert(DumpSharedSpaces, "must be");
(gdb) call CDSHeapVerifier::trace_to_root(tty, orig_module_obj)
[ 0] {0x00000005ce8bb900} jdk.internal.loader.ArchivedClassLoaders::servicesCatalogs (offset = 24)
[ 1] {0x00000005ce8bba08} [Ljdk.internal.module.ServicesCatalog; @[0]
[ 2] {0x00000005ce8bbb60} jdk.internal.module.ServicesCatalog::map (offset = 12)
[ 3] {0x00000005ce8bbb70} java.util.concurrent.ConcurrentHashMap::table (offset = 40)
[ 4] {0x00000005ce8d9638} [Ljava.util.concurrent.ConcurrentHashMap$Node; @[0]
[ 5] {0x00000005ce8d9bc0} java.util.concurrent.ConcurrentHashMap$Node::val (offset = 20)
[ 6] {0x00000005ce8d9b78} java.util.concurrent.CopyOnWriteArrayList::array (offset = 16)
[ 7] {0x00000005ce8d9ba0} [Ljava.lang.Object; @[0]
[ 8] {0x00000005ce8d9b30} jdk.internal.module.ServicesCatalog$ServiceProvider::module (offset = 12)
[ 9] {0x00000005ce8bf588} java.lang.Module

---

Progress

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Issue

• JDK-8298524: Debug function to trace reachability of CDS archived heap objects

Reviewers

• Calvin Cheung (@calvinccheung - Reviewer) ⚠️ Review applies to d6f1a2fa

Reviewing

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[bridgekeeper]

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[openjdk]

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[mlbridge]

Webrevs

• 01: Full - Incremental (6d1d0858)
• 00: Full (d6f1a2fa)

[calvinccheung]

Just one minor comment.

[calvinccheung]

With this change, this function could also be exercised via a debugger. Should the comment be updated?

[iklam]

Thanks for the review. Since the comment a few lines above here mentions gdb, this comment is out-dated, so I deleted it in the latest commit.

[openjdk]

@iklam 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:

8298524: Debug function to trace reachability of CDS archived heap objects

Reviewed-by: ccheung

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 10 new commits pushed to the master branch:

• c3bc4fc: 8297505: Declare fields in some sun.security.pkcs11 classes as final
• c7aca73: 8295857: Clarify that cleanup code can be skipped when the JVM terminates (e.g. when calling halt())
• 781a2e0: 8298343: "Could not confirm if TargetJDK is hardened." warning for SA tests on macosx-aarch64-debug
• 9ff85f6: 8298589: java/net/SctpSanity.java fail with NoClassDefFoundError: sun/nio/ch/sctp/UnsupportedUtil
• 81f57d5: 8298567: Make field in RandomAccessFile final
• 56c438b: 8297822: De-duplicate code in module jdk.sctp
• fabda24: 8296389: C2: PhaseCFG::convert_NeverBranch_to_Goto must handle both orders of successors
• 6c23b4f: 8298480: Remove unused KlassRemSet
• 8e5c331: 8298471: Parallel: Don't keep alive nmethods in Young GC
• d646e32: 8298090: Use String.join() instead of manual loop in DescriptorSupport.toString

Please see this link for an up-to-date comparison between the source branch of this pull request and the master branch.
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.

[iklam]

/integrate

[openjdk]

Going to push as commit 6802277.
Since your change was applied there have been 26 commits pushed to the master branch:

• 23e1827: Merge
• 04b8d0c: 8298084: Memory leak in Method::build_profiling_method_data
• d453190: 8296955: Kitchensink.java failed with "double free or corruption (!prev): "
• 8962c72: 8298488: [macos13] tools/jpackage tests failing with "Exit code: 137" on macOS
• 0267aa5: 8297288: Example code in Scanner class
• cf93933: 8298271: java/security/SignedJar/spi-calendar-provider/TestSPISigned.java failing on Windows
• d624deb: 8298459: Fix msys2 linking and handling out of tree build directory for source zip creation
• 042b706: 8297235: ZGC: assert(regs[i] != regs[j]) failed: Multiple uses of register: rax
• 4081bba: 8297960: G1: Move Root Region Scan Waiting outside collection in logs
• 216775f: 8298144: Remove Space::new_dcto_cl
• ... and 16 more: https://git.openjdk.org/jdk/compare/a37de62d9ddadf1490ee59bd03224e8cea70a75b...master

Your commit was automatically rebased without conflicts.

[openjdk]

@iklam Pushed as commit 6802277.

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