8347463: jdk/jfr/threading/TestManyVirtualThreads.java crashes with assert(oopDesc::is_oop_or_null(val)) #27913

anton-seoane · 2025-10-21T09:19:22Z

This PR introduces a fix for a intermittent assert crash due to a non-oop found in the stack when deoptimizing.

The inline_native_GetEventWriter JFR intrinsic performs a call into the runtime, which can safepoint, to write a checkpoint for the vthread. This call returns a global handle (jobject) that then gets resolved to a raw oop.

However, the corresponding jfr_write_checkpoint_Type does not set any return, modelling the call as void. If a safepoint hits in the small window after the stub returns but before the writer oop is used, and the GC moves the object in that window, the deoptimization path cannot resolve a handle that it never recorded, leading to the subsequent crash.

An IR Framework test is introduced to exercise the error explicitly. Additionally, related documentation in form of comments in the appropriate file (runtime.hpp) is added to hopefully prevent similar cases in the future.

Testing: passes tiers 1-5

Progress

Change must be properly reviewed (1 review required, with at least 1 Reviewer)
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Commit message must refer to an issue

Issue

JDK-8347463: jdk/jfr/threading/TestManyVirtualThreads.java crashes with assert(oopDesc::is_oop_or_null(val)) (Bug - P3)

Reviewers

Roberto Castañeda Lozano (@robcasloz - Reviewer) Review applies to aa09c1bb
Markus Grönlund (@mgronlun - Reviewer) Review applies to 9191c3b3
Dean Long (@dean-long - Reviewer)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/27913/head:pull/27913
$ git checkout pull/27913

Update a local copy of the PR:
$ git checkout pull/27913
$ git pull https://git.openjdk.org/jdk.git pull/27913/head

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Checkout this PR locally:
$ git pr checkout 27913

View PR using the GUI difftool:
$ git pr show -t 27913

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https://git.openjdk.org/jdk/pull/27913.diff

Using Webrev

Link to Webrev Comment

bridgekeeper · 2025-10-21T09:20:45Z

👋 Welcome back aseoane! 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 · 2025-10-21T09:22:50Z

@anton-seoane 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:

8347463: jdk/jfr/threading/TestManyVirtualThreads.java crashes with  assert(oopDesc::is_oop_or_null(val))

Reviewed-by: dlong, rcastanedalo, mgronlun

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 70 new commits pushed to the master branch:

2758c6f: 8368856: Add a method that performs saturating addition of a Duration to an Instant
5a2b0ca: 8339526: C2: store incorrectly removed for clone() transformed to series of loads/stores
20bcf0e: 6400876: (bf) Remove sun.nio.ByteBuffered and related obsolete code
... and 67 more: https://git.openjdk.org/jdk/compare/aaa9fbf6b5a0dda0773a657a986246b407402fa1...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.

As you do not have Committer status in this project an existing Committer must agree to sponsor your change. Possible candidates are the reviewers of this PR (@robcasloz, @mgronlun, @dean-long) but any other Committer may sponsor as well.

➡️ To flag this PR as ready for integration with the above commit message, type /integrate in a new comment. (Afterwards, your sponsor types /sponsor in a new comment to perform the integration).

openjdk · 2025-10-21T09:23:46Z

@anton-seoane The following label will be automatically applied to this pull request:

hotspot-compiler

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 · 2025-10-21T09:31:46Z

Webrevs

robcasloz · 2025-10-21T10:00:03Z

/cc hotspot-jfr

openjdk · 2025-10-21T10:01:20Z

@robcasloz
The hotspot-jfr label was successfully added.

anton-seoane · 2025-10-21T13:00:47Z

Switching back to draft after conversation with @robcasloz, to perform further investigation

…47463

openjdk · 2025-10-23T13:45:39Z

⚠️ @anton-seoane This pull request contains merges that bring in commits not present in the target repository. Since this is not a "merge style" pull request, these changes will be squashed when this pull request in integrated. If this is your intention, then please ignore this message. If you want to preserve the commit structure, you must change the title of this pull request to Merge <project>:<branch> where <project> is the name of another project in the OpenJDK organization (for example Merge jdk:master).

openjdk · 2025-10-23T13:45:56Z

@anton-seoane hotspot has been added to this pull request based on files touched in new commit(s).

robcasloz

Thanks for getting to the bottom of this, Antón! The changeset looks good to me, modulo a few documentation and test comments.
It would be good if someone from the JFR team (@mgronlun or @egahlin?) could have a look at this change as well.

src/hotspot/share/opto/runtime.hpp

test/hotspot/jtreg/compiler/intrinsics/TestReturnOopSetForJFRWriteCheckpoint.java

test/hotspot/jtreg/compiler/intrinsics/TestReturnsOopSetForJFRWriteCheckpoint.java

robcasloz · 2025-10-27T09:07:49Z

test/hotspot/jtreg/compiler/intrinsics/TestReturnsOopSetForJFRWriteCheckpoint.java

+ * @test
+ * @summary Tests that the getEventWriter call to write_checkpoint correctly
+ *          reports returning an oop
+ * @requires vm.hasJFR & vm.continuations


Do we need vm.continuations?

We don't. Removed the requirement

robcasloz · 2025-10-27T09:11:19Z

test/hotspot/jtreg/compiler/intrinsics/TestReturnsOopSetForJFRWriteCheckpoint.java

+ *          reports returning an oop
+ * @requires vm.hasJFR & vm.continuations
+ * @library /test/lib /
+ * @modules jdk.jfr/jdk.jfr.internal


Do we need this?

We don't. Removed as well!

(Referring to line 38 only).

test/hotspot/jtreg/compiler/intrinsics/TestReturnsOopSetForJFRWriteCheckpoint.java

Co-authored-by: Roberto Castañeda Lozano <[email protected]>

…WriteCheckpoint.java Co-authored-by: Roberto Castañeda Lozano <[email protected]>

robcasloz

Thanks! Please test the latest changes, at least through some low tiers, before integration.

anton-seoane · 2025-10-27T15:33:34Z

Reverted the more precise IR Framework check that @robcasloz suggested as the method where the actual call to write_checkpoint happened was not always being inlined, resulting in a failure. I am back to the original check for a non-void return type. Quick check shows no issues (ran tiers 1-3)

dean-long · 2025-10-27T20:49:40Z

test/hotspot/jtreg/compiler/intrinsics/TestReturnsOopSetForJFRWriteCheckpoint.java

+        TestFramework.run();
+    }
+
+    // Crash was due to the returns_oop field not being set


I was confused when I could not find "returns_oop". It turns out the names are CallNode::returns_pointer() and ScopeDesc::return_oop().

Oh, I got them mixed up. I will update things accordingly, thanks!

dean-long · 2025-10-27T20:50:55Z

src/hotspot/share/opto/runtime.hpp

+// Please ensure the return type of the runtime call matches its signature,
+// even if the return value is unused. This is crucial for correct handling
+// of runtime calls that return an oop and may trigger deoptimization
+// on return. See rematerialize_objects() in deoptimization.cpp.


I was wondering why this is only a problem for deoptimization, and not regular safepoints that trigger a GC. But the comment in rematerialize_objects() explains that the return value is not part of the GC oopmap.

robcasloz · 2025-10-28T09:43:30Z

test/hotspot/jtreg/compiler/intrinsics/TestReturnOopSetForJFRWriteCheckpoint.java

+ * @bug 8347463
+ * @requires vm.hasJFR
+ * @library /test/lib /
+ * @run driver compiler.intrinsics.TestReturnsOopSetForJFRWriteCheckpoint


You will have to update this line as well after the class name change.

Oh, right. My bad. Fixed

anton-seoane · 2025-10-29T09:09:20Z

Thanks to all for the reviews and suggestions!

anton-seoane · 2025-10-29T09:09:27Z

/integrate

openjdk · 2025-10-29T09:11:27Z

@anton-seoane
Your change (at version 72202ad) is now ready to be sponsored by a Committer.

robcasloz · 2025-10-29T09:35:26Z

/sponsor

openjdk · 2025-10-29T09:37:36Z

Going to push as commit 8457f38.
Since your change was applied there have been 70 commits pushed to the master branch:

2758c6f: 8368856: Add a method that performs saturating addition of a Duration to an Instant
5a2b0ca: 8339526: C2: store incorrectly removed for clone() transformed to series of loads/stores
20bcf0e: 6400876: (bf) Remove sun.nio.ByteBuffered and related obsolete code
... and 67 more: https://git.openjdk.org/jdk/compare/aaa9fbf6b5a0dda0773a657a986246b407402fa1...master

Your commit was automatically rebased without conflicts.

openjdk · 2025-10-29T09:37:49Z

@robcasloz @anton-seoane Pushed as commit 8457f38.

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

anton-seoane and others added 3 commits October 14, 2025 13:46

Runtime call had void type but actually returned an object

39922ef

Change to a more specific type

2c1c8cf

Merge branch 'openjdk:master' into JDK-8347463

a6225eb

openjdk bot changed the title ~~8347463: jdk/jfr/threading/TestManyVirtualThreads.java crashes with assert(oopDesc::is_oop_or_null(val))~~ 8347463: jdk/jfr/threading/TestManyVirtualThreads.java crashes with assert(oopDesc::is_oop_or_null(val)) Oct 21, 2025

openjdk bot added the hotspot-compiler [email protected] label Oct 21, 2025

anton-seoane marked this pull request as ready for review October 21, 2025 09:25

openjdk bot added the rfr Pull request is ready for review label Oct 21, 2025

openjdk bot added the hotspot-jfr [email protected] label Oct 21, 2025

anton-seoane marked this pull request as draft October 21, 2025 13:00

openjdk bot removed the rfr Pull request is ready for review label Oct 21, 2025

anton-seoane added 3 commits October 23, 2025 15:35

Test for JDK-8347463

4b322a3

Documentation for future similar cases

f25723c

Merge branch 'JDK-8347463' of github.com:anton-seoane/jdk into JDK-83…

df0fa4c

…47463

openjdk bot added the hotspot [email protected] label Oct 23, 2025

Merge branch 'openjdk:master' into JDK-8347463

c85142e

anton-seoane marked this pull request as ready for review October 27, 2025 06:31

openjdk bot added the rfr Pull request is ready for review label Oct 27, 2025

robcasloz suggested changes Oct 27, 2025

View reviewed changes

anton-seoane and others added 3 commits October 27, 2025 10:22

Update src/hotspot/share/opto/runtime.hpp

51fb388

Co-authored-by: Roberto Castañeda Lozano <[email protected]>

Update test/hotspot/jtreg/compiler/intrinsics/TestReturnsOopSetForJFR…

e91cd48

…WriteCheckpoint.java Co-authored-by: Roberto Castañeda Lozano <[email protected]>

Apply review comments

9191c3b

Change test method name

922d03f

robcasloz approved these changes Oct 27, 2025

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openjdk bot added the ready Pull request is ready to be integrated label Oct 27, 2025

Revert to failOn check as getEventWriter is not always inlined

9ff84e7

openjdk bot removed the ready Pull request is ready to be integrated label Oct 27, 2025

Adjust comment

aa09c1b

robcasloz approved these changes Oct 27, 2025

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openjdk bot added the ready Pull request is ready to be integrated label Oct 27, 2025

dean-long reviewed Oct 27, 2025

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Rename test and update comments

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openjdk bot removed the ready Pull request is ready to be integrated label Oct 28, 2025

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openjdk bot removed ready Pull request is ready to be integrated rfr Pull request is ready for review sponsor Pull request is ready to be sponsored labels Oct 29, 2025

8347463: jdk/jfr/threading/TestManyVirtualThreads.java crashes with assert(oopDesc::is_oop_or_null(val)) #27913

8347463: jdk/jfr/threading/TestManyVirtualThreads.java crashes with assert(oopDesc::is_oop_or_null(val)) #27913

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