We've observed a deadlock in leakprofiler::emit_events when the JVM is shut down with Runtime.getRuntime().halt().

Suggestion for resolution:
During investigation, [~egahlin] has commented that JfrEmergencyDump::on_vm_shutdown didn't seem to be designed for being run from Java. Nevertheless, it can be reached from a Java call to Runtime.getRuntime().halt() [1]. To resolve, add a boolean parameter to Jfr::on_vm_shutdown do differentiate the "called from java" case, and in that case to not call JfrEmergencyDump::on_vm_shutdown.

[1] code path:
Runtime.getRuntime().halt()
JVM_Halt
before_exit
Jfr::on_vm_shutdown
JfrEmergencyDump::on_vm_shutdown
post_events
LeakProfiler::emit_events