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

[Vladimir Kozlov]

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
>>>
>