RFR(XS): 8143897 :Weblogic12medrec assert(handler_address == SharedRuntime::compute_compiled_exc_handler(nm, pc, exception, force_unwind, true)) failed: Must be the same

[Jamsheed C m]

Hi Dean,

On 1/29/2016 9:40 AM, Dean Long wrote:
> As you noticed, for this kind of bug the memory is going to consistent 
> by the time the core file is written.
> So to help debug this assert it if happens again, could you change it 
> to something like:
>
> #ifdef ASSERT
>     address computed_address = 
> SharedRuntime::compute_compiled_exc_handler(nm, pc, exception, 
> force_unwind, true);
>     vmassert(handler_address == computed_address, PTR_FORMAT " != " 
> PTR_FORMAT, p2i(handler_address), p2i(computed_address));
> #endif
I got handler_address value in this case. This value was inconsistent 
with value in ExceptionCache.
It was having initial value and that was helpful in figuring out what 
would have went wrong.

I will make this change.

Best Regards,
Jamsheed
>
> dl
>
> On 1/28/2016 8:16 AM, Jamsheed C m wrote:
>> Hi,
>>
>> Please review the fix made for issue
>>
>> bug url: https://bugs.openjdk.java.net/browse/JDK-8143897
>> web rev: http://cr.openjdk.java.net/~thartmann/8143897/webrev.00/
>>
>> Unit tests: As its hard, none
>>
>> Other tests: jprt.
>>
>> Description of the issue:
>> A valid pc match in exception cache returning an invalid handler 
>> makes assert to fail.
>> This happens as  ExceptionCache reads are lock free access.
>>
>> As a fix for this i have put a storestore mem barrier before the 
>> count is updated.
>>
>> Best Regards,
>> Jamsheed
>