We observed 2 asserts recently triggered by gc/shenandoah/oom/TestThreadFailure.java.
One on Windows x86_64, one on Linux Alpine x86_64 .

Windows :
-----------

# Internal Error (d:\priv\jenkins\ci2\client-home\workspace\openjdk-jdk-windows_x86_64-dbg\jdk\src\hotspot\share\gc\shenandoah\shenandoahGenerationalHeap.cpp:761), pid=26744, tid=18236
# assert(young_reserve + reserve_for_mixed + reserve_for_promo <= old_available + young_available) failed: Cannot reserve more memory than is available: 0 + 0 + 271392 <= 89344 + 0

# Problematic frame:
# V [jvm.dll+0xfb591c] ShenandoahGenerationalHeap::compute_old_generation_balance+0x78c

Stack: [0x000000c44cd00000,0x000000c44ce00000], sp=0x000000c44cdfe6c0, free space=1017k
Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
V [jvm.dll+0xfb591c] ShenandoahGenerationalHeap::compute_old_generation_balance+0x78c (shenandoahGenerationalHeap.cpp:759)
V [jvm.dll+0xf97873] ShenandoahGeneration::prepare_regions_and_collection_set+0x393 (shenandoahGeneration.cpp:846)
V [jvm.dll+0xf7b158] ShenandoahDegenGC::op_degenerated+0x418 (shenandoahDegeneratedGC.cpp:198)
V [jvm.dll+0xf7ab52] ShenandoahDegenGC::entry_degenerated+0x272 (shenandoahDegeneratedGC.cpp:84)
V [jvm.dll+0x106320a] VM_ShenandoahDegeneratedGC::doit+0x3a (shenandoahVMOperations.cpp:115)
V [jvm.dll+0x1278977] VM_Operation::evaluate+0xd7 (vmOperations.cpp:75)
V [jvm.dll+0x127a793] VMThread::evaluate_operation+0xe3 (vmThread.cpp:285)
V [jvm.dll+0x127aec1] VMThread::inner_execute+0x241 (vmThread.cpp:424)
V [jvm.dll+0x127b4d4] VMThread::run+0x114 (vmThread.cpp:177)
V [jvm.dll+0x11c938e] Thread::call_run+0x1be (thread.cpp:248)
V [jvm.dll+0xe2f614] thread_native_entry+0xc4 (os_windows.cpp:556)
C [ucrtbase.dll+0x2268a] (no source info available)
C [KERNEL32.DLL+0x17ac4] (no source info available)
C [ntdll.dll+0x5a8c1] (no source info available)

Registers:
RAX=0x000002861d7c0000, RBX=0xffffffffffffffff, RCX=0x00007fff5e3d89a0, RDX=0x00000000000002f9
RSP=0x000000c44cdfe6c0, RBP=0x000002861e4f7b40, RSI=0x0000000000000000, RDI=0x0000000000042420
R8 =0x00007fff5e3d90d0, R9 =0x00007fff5e3d9080, R10=0x0000000000000001, R11=0x000000c44cdfe6b0
R12=0x0000000000000000, R13=0x0000000000000001, R14=0x0000000000000000, R15=0x0000000000015d00
RIP=0x00007fff5dd3591c, EFLAGS=0x0000000000010202

XMM[0]=0x0000000000000000 0x4110908000000000
XMM[1]=0x0000000000000000 0x0000000000000000
XMM[2]=0x0000000000000000 0x3fd46a7ef9db22d1
XMM[3]=0x0000000000003c40 0x000002861ec14380
XMM[4]=0x0000000000000000 0x0000000000000000
XMM[5]=0x0000000000000000 0x0000000000000000
XMM[6]=0x0000000000000000 0x43e0000000000000
XMM[7]=0x0000000000000000 0x0000000000000000
XMM[8]=0x0000000000000000 0x0000000000000000
XMM[9]=0x0000000000000000 0x0000000000000000
XMM[10]=0x0000000000000000 0x0000000000000000
XMM[11]=0x0000000000000000 0x0000000000000000
XMM[12]=0x0000000000000000 0x0000000000000000
XMM[13]=0x0000000000000000 0x0000000000000000
XMM[14]=0x0000000000000000 0x0000000000000000
XMM[15]=0x0000000000000000 0x0000000000000000
  MXCSR=0x00001fa0


Linux Alpine :
----------------

# Internal Error (/priv/jenkins/ci1/client-home/workspace/openjdk-jdk-dev-linux_alpine_x86_64-dbg/jdk/src/hotspot/share/gc/shenandoah/shenandoahGenerationalHeap.cpp:759), pid=20990, tid=21171
# assert(young_reserve + reserve_for_mixed + reserve_for_promo <= old_available + young_available) failed: Cannot reserve more memory than is available: 611616 + 0 + 276326 <= 110904 + 611616

# Problematic frame:
# V [libjvm.so+0x1ab949f] ShenandoahGenerationalHeap::compute_old_generation_balance(unsigned long, unsigned long, unsigned long)+0x43f

Stack: [0x00007fdb41e16000,0x00007fdb41f16ab0], sp=0x00007fdb41f15a30, free space=1022k
Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
V [libjvm.so+0x1ab949f] ShenandoahGenerationalHeap::compute_old_generation_balance(unsigned long, unsigned long, unsigned long)+0x43f (shenandoahGenerationalHeap.cpp:759)
V [libjvm.so+0x1aa9586] ShenandoahGeneration::prepare_regions_and_collection_set(bool)+0xc16 (shenandoahGeneration.cpp:844)
V [libjvm.so+0x1a6f1fe] ShenandoahDegenGC::op_prepare_evacuation()+0x5e (shenandoahDegeneratedGC.cpp:351)
V [libjvm.so+0x1a702b0] ShenandoahDegenGC::op_degenerated()+0x270 (shenandoahDegeneratedGC.cpp:198)
V [libjvm.so+0x1a712b5] ShenandoahDegenGC::entry_degenerated()+0x1c5 (shenandoahDegeneratedGC.cpp:83)
V [libjvm.so+0x1bd35ed] VM_ShenandoahDegeneratedGC::doit()+0x5d (shenandoahVMOperations.cpp:115)
V [libjvm.so+0x1ec5a46] VM_Operation::evaluate()+0x196 (vmOperations.cpp:74)
V [libjvm.so+0x1ee255b] VMThread::evaluate_operation(VM_Operation*)+0x5eb (vmThread.cpp:284)
V [libjvm.so+0x1ee2fff] VMThread::inner_execute(VM_Operation*)+0x42f (vmThread.cpp:421)
V [libjvm.so+0x1ee3194] VMThread::loop()+0x84 (vmThread.cpp:487)
V [libjvm.so+0x1ee32a4] VMThread::run()+0x94 (vmThread.cpp:177)
V [libjvm.so+0x1dc4836] Thread::call_run()+0xb6 (thread.cpp:243)
V [libjvm.so+0x1840c9c] thread_native_entry(Thread*)+0x17c (os_linux.cpp:929)
Registers:
RAX=0x00007fdb5fc26000, RBX=0x00007fdb5d2503e0, RCX=0x00007fdb5f632100, RDX=0x00007fdb5f632150
RSP=0x00007fdb41f15a30, RBP=0x00007fdb41f15a90, RSI=0x00000000000002f7, RDI=0x00007fdb5f631ec0
R8 =0x0000000000024ec7, R9 =0x0000000000000000, R10=0x0000000000000000, R11=0x0000000000000000
R12=0xffffffffffffffff, R13=0x0000000000000000, R14=0x000000000001b138, R15=0x0000000000043766
RIP=0x00007fdb5eeb949f, EFLAGS=0x0000000000010287, CSGSFS=0x002b000000000033, ERR=0x0000000000000006
  TRAPNO=0x000000000000000e

XMM[0]=0x0000000000000000 0x4110dd9999999999
XMM[1]=0x0000000000000000 0x43e0000000000000
XMM[2]=0x0000000000000000 0x43efffffffffffab
XMM[3]=0x0000000000000000 0x4138999900000000
XMM[4]=0x0000000000000000 0x4152733300000000
XMM[5]=0x0000000000000000 0x3fa73aa97b11a468
XMM[6]=0x0000000000000000 0x400a53f7ced91687
XMM[7]=0x0000000000000000 0x0000000000000000
XMM[8]=0x0000000000000000 0x0000000000000000
XMM[9]=0x0000000000000000 0x0000000000000000
XMM[10]=0x0000000000000000 0x0000000000000000
XMM[11]=0xffffffffffffffff 0xffffffffffffffff
XMM[12]=0x0000000000000001 0x0000000000000001
XMM[13]=0x0000000000000000 0x0000000000000000
XMM[14]=0x0000000000000000 0x0000000000000000
XMM[15]=0xcafebabecafebabe 0xcafebabecafebabe
  MXCSR=0x00001fa2