Seen in recently added 11u GHA, but not elsewhere (since CMS is removed going forward).

Reproducible as:

$ cd test/hotspot/jtreg/gc/stress/gcbasher
$ javac *.java
$ ~/trunks/shipilev-jdk11u-dev/build/linux-x86-normal-server-fastdebug/images/jdk/bin/java -Xlog:gc*=info -Xmx256m -server -XX:+UseConcMarkSweepGC TestGCBasher 120000
...

# Internal Error (/home/shade/trunks/shipilev-jdk11u-dev/src/hotspot/share/gc/shared/blockOffsetTable.cpp:562), pid=158474, tid=158492
# assert(n > q) failed: Looping at n = 0x5a4777bc with last = 0xdf907c00, while querying blk_start(0xe2870000) on _sp = [0xdbb50000,0xe6600000)

Current thread (0xd574c800): GCTaskThread "GC Thread#3" [stack: 0xd2180000,0xd2200000] [id=158492]

Stack: [0xd2180000,0xd2200000], sp=0xd21feca0, free space=507k
Native frames: (J=compiled Java code, A=aot compiled Java code, j=interpreted, Vv=VM code, C=native code)
V [libjvm.so+0x1788b60] VMError::report_and_die(int, char const*, char const*, char*, Thread*, unsigned char*, void*, void*, char const*, int, unsigned int)+0x400
V [libjvm.so+0x1789b26] VMError::report_and_die(Thread*, void*, char const*, int, char const*, char const*, char*)+0x36
V [libjvm.so+0xa8aa01] report_vm_error(char const*, int, char const*, char const*, ...)+0x81
V [libjvm.so+0x635f41] BlockOffsetArrayNonContigSpace::block_start_unsafe(void const*) const+0x391
V [libjvm.so+0x932736] CMSCardTable::process_chunk_boundaries(Space*, DirtyCardToOopClosure*, MemRegion, MemRegion, signed char**, unsigned int, unsigned int)+0x96
V [libjvm.so+0x934b35] CMSCardTable::process_stride(Space*, MemRegion, int, int, OopsInGenClosure*, CardTableRS*, signed char**, unsigned int, unsigned int)+0x2a5
V [libjvm.so+0x935055] CMSCardTable::non_clean_card_iterate_parallel_work(Space*, MemRegion, OopsInGenClosure*, CardTableRS*, unsigned int)+0xa5
V [libjvm.so+0x7e5fb2] CardTableRS::younger_refs_in_space_iterate(Space*, OopsInGenClosure*, unsigned int)+0xf2
V [libjvm.so+0x7d54b0] CardGeneration::younger_refs_iterate(OopsInGenClosure*, unsigned int)+0x40
V [libjvm.so+0xd11ade] GenCollectedHeap::young_process_roots(StrongRootsScope*, OopsInGenClosure*, OopsInGenClosure*, CLDClosure*, OopStorage::ParState<false, false>*)+0x8e
V [libjvm.so+0x1413d6c] ParNewGenTask::work(unsigned int)+0x18c
V [libjvm.so+0x1814158] GangWorker::run_task(WorkData)+0x68
V [libjvm.so+0x18142aa] GangWorker::loop()+0x3a