RFR: 8252921: NMT overwrite memory type for region assert when building dynamic archive [v5]

[Ioi Lam]

On Mon, 21 Sep 2020 03:42:25 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> Zhengyu Gu has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Fix metaspace remapping on Windows
>
> src/hotspot/share/runtime/thread.cpp line 1341:
> 
>> 1339:   unregister_thread_stack_with_NMT();
>> 1340:   set_stack_base(NULL);
>> 1341:   set_stack_size(0);
> 
> Sorry but I just don't see any need for clearing stack_base or stack_size, and then you don't need to mess with the
> assertion in stack_base().

I agree with David that the calls to `set_stack_base(NULL); set_stack_size(0);` do not seem to be related to this bug.
Also, previously only `set_stack_base(NULL);` was called -- on all Threads. Now:

- NonJavaThread: `set_stack_base(NULL); set_stack_size(0);`
- JavaThread: neither operation is done

I am wondering:

- why the behavior is changed
- is zeroing the stack_base/size necessary for NMT code only, or is it necessary for non-NMT operations as well?

Will any test cases fail if you remove line 1340/1341?

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PR: https://git.openjdk.java.net/jdk/pull/185