RFR: 8364090: Dump JFR recording on CrashOnOutOfMemoryError [v2]

[Yasumasa Suenaga]

On Sat, 26 Jul 2025 16:54:33 GMT, Erik Gahlin <egahlin at openjdk.org> wrote:

>> Yasumasa Suenaga has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Rename is_oom to emit_old_object_samples
>
> src/hotspot/share/jfr/recorder/repository/jfrEmergencyDump.cpp line 563:
> 
>> 561:     LeakProfiler::emit_events(max_jlong, false, false);
>> 562:   } else {
>> 563:     EventShutdown e;
> 
> Do you know why EventShutDown is not always emitted?
> 
> Is it emitted from somewhere else, so we would get two events if we always emitted it here?
> 
> I know it was this way before your change, but I’d like to understand why. We may want to add another parameter or write a comment to explain the behavior.

We have two call path to emit `EventShutdown`.

In case of the most of OOM which triggers VM shutdown (e.g. OOM happend on the last non-daemon thread), `Threads::destroy_vm()` should be called, and `Jfr::on_vm_shutdown()` would be called via `before_exit` @ java.cpp .

`Threads::destroy_vm()` @ src/hotspot/share/runtime/threads.cpp

  EventShutdown e;
  if (e.should_commit()) {
    e.set_reason("No remaining non-daemon Java threads");
    e.commit();
  }

  // Hang forever on exit if we are reporting an error.
  if (ShowMessageBoxOnError && VMError::is_error_reported()) {
    os::infinite_sleep();
  }
  os::wait_for_keypress_at_exit();

  // run Java level shutdown hooks
  thread->invoke_shutdown_hooks();

  before_exit(thread);


In case of `exception_handler` - `VMError::report_and_die()` in this case - `EventShutdown` would be emitted at `post_events()`, however `LeakProfiler::emit_events()` would not be called.

I think both `EventShutdown` and LeakProfiler should be emitted when the crash happens due to `-XX:+CrashOnOutOfMemoryError`. So I will add another parameter to enforce to emit `EventShutdown` in this case.

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PR Review Comment: https://git.openjdk.org/jdk/pull/26468#discussion_r2233594799