RFR (M) JDK-8163406: The fixup_module_list must be protected by Module_lock when inserting new entries

[Zhengyu Gu]

3) in javaClasses
>>>
>>> Lines 856, 865: do you need a load_module_acquire when you read
>>> javabase_entry->module() in the assertion?
>> Completed, thanks for pointing that out.  New webrev based on your and
>> Coleen's comments at:
>>
>> http://cr.openjdk.java.net/~lfoltan/bug_jdk8163406.1/webrev/
>
> In this updated code:
>
>  803     assert(Universe::is_module_initialized() ||
>  804            (ModuleEntryTable::javabase_defined() &&
>  805             (module() == 
> JNIHandles::resolve(ModuleEntryTable::javabase_moduleEntry()->module_load_acquire()))),
>  806            "Incorrect java.lang.reflect.Module specification 
> while creating mirror");
>
> you are doubling up on the load-acquire because it is already inside 
> javabase_defined(). Whether you need the load-acquire in 
> javabase_defined() depends on the context in which javabase_defined() 
> is called - which isn't completely clear to me.
>
javabase_defined() itself does not need load-acquire, it looks like an 
unexpected side-effect to me. I would rather see explicit
module_load_acquire() call than depending on this side-effect to ensure 
ordered access.

-Zhengyu

> David
> ----
>
>> Thank you for reviewing!
>> Lois
>>
>>>
>>> thanks,
>>> Karen
>>>
>>>
>>>> On Sep 7, 2016, at 11:31 AM, Lois Foltan <lois.foltan at oracle.com> 
>>>> wrote:
>>>>
>>>> Hello,
>>>>
>>>> Please review the following fix:
>>>>
>>>> Webrev:
>>>> http://cr.openjdk.java.net/~lfoltan/bug_jdk8163406/webrev/
>>>>
>>>> Bug: The fixup_module_list must be protected by Module_lock when
>>>> inserting new entries
>>>> https://bugs.openjdk.java.net/browse/JDK-8163406
>>>>
>>>> Summary:
>>>> During bootstrapping, after the load of java.lang.Class, the method
>>>> java_lang_Class::create_mirror() is multi-threaded.  Before java.base
>>>> is defined to the VM, the fixup_module_list stores all classes that
>>>> once java.base is defined, must have their module field patched with
>>>> java.base's java.lang.reflect.Module.  Insertion of a class into the
>>>> fixup_module_list must be protected via Module_lock. Included in this
>>>> fix is correct order access store and load of the
>>>> java.lang.reflect.Module field for java.base's ModuleEntry. Thank
>>>> you to David Holmes for guidance on this piece.
>>>>
>>>> Testing:
>>>> Full hotspot nightly testing, JCK vm & lang, several iterations of
>>>> jaxp tests to test JDK-8164721
>>