[lworld] RFR: 8341844: [lworld] Test crashing in genzgc in ZBarrier::mark_from_old_slow_path(zaddress)+0x4c

[Frederic Parain]

On Tue, 17 Dec 2024 20:02:03 GMT, David Simms <dsimms at openjdk.org> wrote:

> Generational zgc requires a store barrier in addition to the load barrier.
> load barrier followed by bulk copy isn't enough

src/hotspot/share/gc/z/zBarrierSet.inline.hpp line 499:

> 497:     //   2) load and store barrier for each oop
> 498:     //   3) possibly raw copy for any primitive payload trailer
> 499:     assert(lk == NON_ATOMIC_FLAT || lk == PAYLOAD, "Cannot support layout other than NON_ATOMIC_FLAT"); // Note: PAYLOAD is incorrect, resolve when transistioned to new flattening

Why is PAYLOAD incorrect here?
And what about ATOMIC_FLAT? Even with ZGC, it can contain an oop.

-------------

PR Review Comment: https://git.openjdk.org/valhalla/pull/1321#discussion_r1889258598