thread '<unnamed>' panicked at '2011a252000: VO bit not set'

[qinsoon]

We observed this assertion failure in the run https://github.com/mmtk/mmtk-julia/actions/runs/10072749493/job/27845322903?pr=161 for #161. This PR was merging the object reference alignment changes from MMTk core, and it turns on VO bit unconditionally (MMTK_CONSERVATIVE=1 in Make.user, and default = ["mmtk/vm_space", "julia_copy_stack", "object_pinning", "is_mmtk_object"] in Cargo.toml).

It is unclear if this is a Julia bug or a mmtk-core bug.

[2024-07-24T08:08:10Z INFO  mmtk_julia::collection] stop_all_mutators: visiting VMMutatorThread(VMThread(OpaquePointer(0x7f71a8000b70)))
thread '<unnamed>' panicked at '2011a252000: VO bit not set', /home/runner/.cargo/git/checkouts/mmtk-core-3306bdeb8eb4322b/a3a72f8/src/util/metadata/vo_bit/helper.rs:144:9
stack backtrace:
   0: rust_begin_unwind
             at /rustc/eb26296b556cef10fb713a38f3d16b9886080f26/library/std/src/panicking.rs:593:5
   1: core::panicking::panic_fmt
             at /rustc/eb26296b556cef10fb713a38f3d16b9886080f26/library/core/src/panicking.rs:67:14
   2: mmtk::util::metadata::vo_bit::helper::on_trace_object
             at /home/runner/.cargo/git/checkouts/mmtk-core-3306bdeb8eb4322b/a3a72f8/src/util/metadata/vo_bit/helper.rs:144:9
   3: mmtk::policy::immix::immixspace::ImmixSpace<VM>::trace_object_without_moving
             at /home/runner/.cargo/git/checkouts/mmtk-core-3306bdeb8eb4322b/a3a72f8/src/policy/immix/immixspace.rs:555:9
   4: <mmtk::policy::immix::immixspace::ImmixSpace<VM> as mmtk::policy::gc_work::PolicyTraceObject<VM>>::trace_object
             at /home/runner/.cargo/git/checkouts/mmtk-core-3306bdeb8eb4322b/a3a72f8/src/policy/immix/immixspace.rs:193:13
   5: <mmtk::plan::immix::global::Immix<VM> as mmtk::plan::global::PlanTraceObject<VM>>::trace_object
             at /home/runner/.cargo/git/checkouts/mmtk-core-3306bdeb8eb4322b/a3a72f8/src/plan/immix/global.rs:28:21
   6: <mmtk::scheduler::gc_work::PlanProcessEdges<VM,P,_> as mmtk::scheduler::gc_work::ProcessEdgesWork>::trace_object
             at /home/runner/.cargo/git/checkouts/mmtk-core-3306bdeb8eb4322b/a3a72f8/src/scheduler/gc_work.rs:935:9
   7: <mmtk::scheduler::gc_work::PlanProcessEdges<VM,P,_> as mmtk::scheduler::gc_work::ProcessEdgesWork>::process_slot
             at /home/runner/.cargo/git/checkouts/mmtk-core-3306bdeb8eb4322b/a3a72f8/src/scheduler/gc_work.rs:944:26
   8: mmtk::scheduler::gc_work::ProcessEdgesWork::process_slots
             at /home/runner/.cargo/git/checkouts/mmtk-core-3306bdeb8eb4322b/a3a72f8/src/scheduler/gc_work.rs:634:13
   9: mmtk::scheduler::gc_work::<impl mmtk::scheduler::work::GCWork<<E as mmtk::scheduler::gc_work::ProcessEdgesWork>::VM> for E>::do_work
             at /home/runner/.cargo/git/checkouts/mmtk-core-3306bdeb8eb4322b/a3a72f8/src/scheduler/gc_work.rs:642:9
  10: mmtk::scheduler::work::GCWork::do_work_with_stat
             at /home/runner/.cargo/git/checkouts/mmtk-core-3306bdeb8eb4322b/a3a72f8/src/scheduler/work.rs:45:9
  11: mmtk::scheduler::worker::GCWorker<VM>::run
             at /home/runner/.cargo/git/checkouts/mmtk-core-3306bdeb8eb4322b/a3a72f8/src/scheduler/worker.rs:244:13
  12: mmtk::memory_manager::start_worker
             at /home/runner/.cargo/git/checkouts/mmtk-core-3306bdeb8eb4322b/a3a72f8/src/memory_manager.rs:492:5
  13: <mmtk_julia::collection::VMCollection as mmtk::vm::collection::Collection<mmtk_julia::JuliaVM>>::spawn_gc_thread::{{closure}}
             at /home/runner/work/mmtk-julia/mmtk-julia/mmtk/src/collection.rs:95:21
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

Command line (using the CI's Make.user)

cargo build --features immix,non_moving
MMTK_PLAN=Immix MMTK_BUILD=debug MMTK_TPIN_ROOTS=0 make