8303086: SIGSEGV in JavaThread::is_interp_only_mode()

[sspitsyn]

The JVMTI function SetEventNotificationMode can set notification mode globally (event_thread == nullptr) for all threads or for a specific thread (event_thread != nullptr). To get a stable mount/unmount vision of virtual threads a JvmtiVTMSTransitionDisabler helper object is created :
JvmtiVTMSTransitionDisabler disabler(event_thread);

In a case if event_thread == nullptr the VTMS transitions are disabled for all virtual thread,
otherwise they are disabled for a specific thread if it is virtual.
The call to JvmtiEventController::set_user_enabled() makes a call to recompute_enabled() at the end of its work to do a required bookkeeping. As part of this work, the recompute_thread_enabled(state) is called for each thread from the ThreadsListHandle, not only for the given event_thread:

    ThreadsListHandle tlh;
    for (; state != nullptr; state = state->next()) {
      any_env_thread_enabled |= recompute_thread_enabled(state);
    }

This can cause crashes as VTMS transitions for other virtual threads are allowed.
Crashes are observed in this small function:

  bool is_interp_only_mode() {
    return _thread == nullptr ? _saved_interp_only_mode != 0 : _thread->is_interp_only_mode();
  }

In a case _thread != nullptr then the call needs to be executed: _thread->is_interp_only_mode().
But the filed _thread can be already changed to nullptr by a VTMS transition.

The fix is to always disable all transitions.
Thanks to Dan and Patricio for great analysis of this crash!

Testing:

• In progress: mach5 tiers 1-6

---

Progress

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Issue

• JDK-8303086: SIGSEGV in JavaThread::is_interp_only_mode() (Bug - P3)

Reviewers

• Patricio Chilano Mateo (@pchilano - Reviewer)
• Chris Plummer (@plummercj - Reviewer)
• Leonid Mesnik (@lmesnik - Reviewer)

Reviewing

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[bridgekeeper]

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[mlbridge]

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• 00: Full (45482b4e)

[pchilano]

Looks good to me!

Patricio

[openjdk]

@sspitsyn 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:

8303086: SIGSEGV in JavaThread::is_interp_only_mode()

Reviewed-by: pchilanomate, cjplummer, lmesnik

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At the time when this comment was updated there had been 6 new commits pushed to the master branch:

• 19601eb: 8310993: Missing @SInCE tags in jdk.attach
• e8ff74c: 8310987: Missing @SInCE tag(s) in java/util/logging/ErrorManager.java
• e3a7e02: 8311162: Simplify and modernize equals and hashCode for java.net
• 430d6b6: 8309976: Add microbenchmark for stressing code cache
• 33011ea: 8310946: G1: Refactor G1Policy::next_gc_should_be_mixed
• a7d168b: 8311026: Some G1 specific tests do not set -XX:+UseG1GC

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[sspitsyn]

Patricio, Chris and Leonid, thank you for review.

[sspitsyn]

/integrate

[openjdk]

Going to push as commit 971c2ef.
Since your change was applied there have been 8 commits pushed to the master branch:

• f6bdccb: 8310829: guarantee(!HAS_PENDING_EXCEPTION) failed in ExceptionTranslation::doit
• 456bf11: 8310173: Update --release 21 symbol information for JDK 21 build 29
• 19601eb: 8310993: Missing @SInCE tags in jdk.attach
• e8ff74c: 8310987: Missing @SInCE tag(s) in java/util/logging/ErrorManager.java
• e3a7e02: 8311162: Simplify and modernize equals and hashCode for java.net
• 430d6b6: 8309976: Add microbenchmark for stressing code cache
• 33011ea: 8310946: G1: Refactor G1Policy::next_gc_should_be_mixed
• a7d168b: 8311026: Some G1 specific tests do not set -XX:+UseG1GC

Your commit was automatically rebased without conflicts.

[openjdk]

@sspitsyn Pushed as commit 971c2ef.

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

[dholmes-ora]

An explanatory comment would have been good.

[sspitsyn]

The fix has been already integrated.
I'll add a comment when there is a chance.

[sspitsyn]

/backport jdk21

[openjdk]

@sspitsyn the backport was successfully created on the branch sspitsyn-backport-971c2efb in my personal fork of openjdk/jdk21. To create a pull request with this backport targeting openjdk/jdk21:master, just click the following link:

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Hi all,

This pull request contains a backport of commit 971c2efb from the openjdk/jdk repository.

The commit being backported was authored by Serguei Spitsyn on 30 Jun 2023 and was reviewed by Patricio Chilano Mateo, Chris Plummer and Leonid Mesnik.

Thanks!

If you need to update the source branch of the pull then run the following commands in a local clone of your personal fork of openjdk/jdk21:

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$ git checkout sspitsyn-backport-971c2efb
# make changes
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$ git commit --message 'Describe additional changes made'
$ git push https://github.com/openjdk-bots/jdk21.git sspitsyn-backport-971c2efb