RFR(S): JDK-8137035 tests got EXCEPTION_STACK_OVERFLOW on Windows 64 bit

[David Holmes]

On 31/08/2016 9:04 AM, Frederic Parain wrote:
> Hi David,
>
> On 08/29/2016 11:10 PM, David Holmes wrote:
>> Hi Fred,
>
>>>> While examining the thread state logic in the exception handler I
>>>> noticed some pre-existing bugs:
>>>>
>>>> 2506   if (exception_code == EXCEPTION_ACCESS_VIOLATION) {
>>>> 2507     JavaThread* thread = (JavaThread*) t;
>>>>
>>>> there is no check that t is in fact a JavaThread, or even that t is
>>>> non-NULL. Such checks occur slightly later:
>>>
>>> I've investigated this issue, and it is currently harmless.
>>> The casted pointer is only used to call a method requiring
>>> a JavaThread* pointer and the only usage of its argument it's
>>> a NULL check. Unfortunately, fixing this issue would require
>>> to modify the prototype of os::is_memory_serialize_page()
>>> and propagate the change across all platforms using it.
>>> It's a wider scope fix than JDK-8137035.
>>
>> I was only expecting you to move (if the scoping allows it, else copy)
>> the later:
>
> The scoping doesn't allow his move, and adding the test would
> potentially change the behavior (I'm expecting that only JavaThreads
> could be blocked on the serialization page, but I might be wrong).

If we were to find that a non-JavaThread were executing that code that 
would be a significant bug I think. I really think this needs to be 
fixed to ensure it is a JavaThread - even if you only add an assert.

Thanks,
David

> Fred
>
>> if (t != NULL && t->is_Java_thread()) {
>>
>> check. ;)
>>
>> Thanks,
>> David
>>
>>> I've added a comment the unsafe cast in os_windows.cpp file,
>>> highlighting the fact it was unsafe, and explaining why it
>>> is currently harmless.
>>>
>>>>
>>>> 2523   if (t != NULL && t->is_Java_thread()) {
>>>> 2524     JavaThread* thread = (JavaThread*) t;
>>>>
>