On Mon, 9 Sep 2024 18:15:38 GMT, Coleen Phillimore <cole...@openjdk.org> wrote:
>> Roman Kennke has updated the pull request incrementally with six additional
>> commits since the last revision:
>>
>> - Print as warning when UCOH doesn't match in CDS archive
>> - Improve initialization of mark-word in CDS ArchiveHeapWriter
>> - Simplify getKlass() in SA
>> - Simplify oopDesc::init_mark()
>> - Get rid of forward_safe_* methods
>> - GCForwarding touch-ups
>
> src/hotspot/share/oops/typeArrayKlass.cpp line 175:
>
>> 173: size_t TypeArrayKlass::oop_size(oop obj) const {
>> 174: // In this assert, we cannot safely access the Klass* with compact
>> headers.
>> 175: assert(UseCompactObjectHeaders || obj->is_typeArray(),"must be a type
>> array");
>
> Why not? I think I'm missing something. Klass should be in the markWord and
> that should be ok (?)
I tracked this down to only (at least in my testing) happen from
`size_given_klass` when called from the GC when it is about to copy an object.
While that happens another thread can racingly succeed to copy the object and
install a forwarding pointer over the old copy. When that happens the klass
pointer is broken and the call to oopDesc::is_typeArray() crashes.
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/20677#discussion_r1750862842
