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]

Thanks Vladimir.

Best Regards,
Jamsheed

On 2/3/2016 11:31 PM, Vladimir Kozlov wrote:
> Looks good.
>
> Thanks,
> Vladimir
>
> On 2/3/16 1:56 AM, Jamsheed C m wrote:
>> Hi Vladimir, Chris,
>>
>> On 1/29/2016 6:22 AM, Vladimir Kozlov wrote:
>>> On 1/28/16 12:29 PM, Jamsheed C m wrote:
>>>>
>>>>
>>>> On 1/29/2016 12:15 AM, Christian Thalinger wrote:
>>>>>     if (count() < cache_size) {
>>>>>       set_pc_at(count(),addr);
>>>>>       set_handler_at(count(), handler);
>>>>>
>>>>> Shouldn’t we read count() only once into a local variable to rule 
>>>>> any odd race bugs down the road?
>>>
>>> +1. As I understand, Chris is suggesting to do it in addition to 
>>> storestore barrier.
>> I have made the suggested change.
>> http://cr.openjdk.java.net/~thartmann/8143897/webrev.01/
>>
>> Best Regards,
>> Jamsheed
>>
>>>
>>> Do we have other similar code?
>>>
>>> Thanks,
>>> Vladimir
>>>
>>>>
>>>> write to cache is mutex lock protected. so this code is safe.
>>>>
>>>> Issue is seen in weak memory order machines.  lockless read of 
>>>> exception cache values fails as writes in cache get
>>>> reordered.
>>>>
>>>> Best Regards,
>>>> Jamsheed
>>>>>
>>>>>> On Jan 28, 2016, at 5:16 PM, Jamsheed C m 
>>>>>> <jamsheed.c.m at oracle.com> 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
>>>>
>>