Various tests are failing with SIGSEGV in the Compiler thread.

For the first sighting:

compiler/codegen/TestLongDoubleVect.java

# SIGSEGV (0xb) at pc=0x00007fa529de1d30, pid=19074, tid=19089
#
# JRE version: Java(TM) SE Runtime Environment (16.0+25) (fastdebug build 16-ea+25-1585)
# Java VM: Java HotSpot(TM) 64-Bit Server VM (fastdebug 16-ea+25-1585, compiled mode, sharing, g1 gc, linux-amd64)
# Problematic frame:
# V [libjvm.so+0x978d30] ClassLoaderData::is_alive() const+0x0

Here's the crashing thread's stack:

--------------- T H R E A D ---------------

Current thread (0x00007fa524318cd0): JavaThread "C2 CompilerThread0" daemon [_thread_in_vm, id=19089, stack(0x00007fa48ddfe000,0x00007fa48deff000)]

Stack: [0x00007fa48ddfe000,0x00007fa48deff000], sp=0x00007fa48defdbe8, free space=1022k
Native frames: (J=compiled Java code, A=aot compiled Java code, j=interpreted, Vv=VM code, C=native code)
V [libjvm.so+0x978d30] ClassLoaderData::is_alive() const+0x0
V [libjvm.so+0xa0652b] CompileQueue::get()+0x10b
V [libjvm.so+0xa0a0b5] CompileBroker::compiler_thread_loop()+0x2f5
V [libjvm.so+0x1886786] JavaThread::thread_main_inner()+0x256
V [libjvm.so+0x188d440] Thread::call_run()+0x100
V [libjvm.so+0x156da56] thread_native_entry(Thread*)+0x116


siginfo: si_signo: 11 (SIGSEGV), si_code: 1 (SEGV_MAPERR), si_addr: 0x000000000000002c