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

[Frederic Parain]

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).

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;
>>>