RFR: 8309663: test fails "assert(check_alignment(result)) failed: address not aligned: 0x00000008baadbabe"

[Serguei Spitsyn]

On Wed, 14 Jun 2023 19:28:23 GMT, Alex Menkov <amenkov at openjdk.org> wrote:

>> src/hotspot/share/prims/jvmtiTagMap.cpp line 2325:
>> 
>>> 2323:         // Need to apply load barriers for unmounted vthreads.
>>> 2324:         nmethod* nm = jvf->cb()->as_nmethod();
>>> 2325:         nm->run_nmethod_entry_barrier();
>> 
>> This looks good in general.
>> However, I'm looking at the `stackChunkOopDesc::do_barriers0()` implementation and wonder if a similar trick is needed for interpreter frames (to support `Class Redefinition`):
>> 
>> template <stackChunkOopDesc::BarrierType barrier, ChunkFrames frame_kind, typename RegisterMapT>
>> void stackChunkOopDesc::do_barriers0(const StackChunkFrameStream<frame_kind>& f, const RegisterMapT* map) {
>>   // We need to invoke the write barriers so as not to miss oops in old chunks that haven't yet been concurrently scanned
>>   assert (!f.is_done(), "");
>> 
>>   if (f.is_interpreted()) {
>>     Method* m = f.to_frame().interpreter_frame_method();
>>     // Class redefinition support
>>     m->record_gc_epoch();
>>   } else if (f.is_compiled()) {
>>     nmethod* nm = f.cb()->as_nmethod();
>>     // The entry barrier takes care of having the right synchronization
>>     // when keeping the nmethod alive during concurrent execution.
>>     nm->run_nmethod_entry_barrier();
>>     // There is no need to mark the Method, as class redefinition will walk the
>>     // CodeCache, noting their Methods
>>   }
>>   . . .
>
>> This looks good in general. However, I'm looking at the `stackChunkOopDesc::do_barriers0()` implementation and wonder if a similar trick is needed for interpreter frames (to support `Class Redefinition`):
>> 
> 
> This code collects references from thread stack, I don't see how class redefinition can affect them

Thanks. I agree with it.
The stackChunkOopDesc implementation needs it as it does some stack chunk updates.

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

PR Review Comment: https://git.openjdk.org/jdk/pull/14460#discussion_r1231803017