RFR: 8016538: volatile double access via Unsafe.cpp is not atomic

[Yumin Qi]

Hi, David

   Tested on arm/ppc multiple runs and no regression found. Thanks 
Vladimir D for help find machines.
   The tests were conducted on
   1) Windows 32/64
   2) Solaris 32/64
   3) Linux 32/64 (x86/64)
   4) Arm
   5 PPC

   I will push the changes to hotspot-rt.

Thanks
Yumin

On 7/11/2013 8:11 PM, David Holmes wrote:
> Thanks Yumin this all looks good to me.
>
> Of course we need to ensure the concurrency stress tests pass on all 
> platforms.
>
> David
> -----
>
> On 12/07/2013 5:17 AM, Yumin Qi wrote:
>> Hi,  Vladimir and all
>>
>>    New webrev
>> http://cr.openjdk.java.net/~minqi/8016538/03
>> <http://cr.openjdk.java.net/%7Eminqi/8016538/03>
>>
>>    Changed for other x86 platforms too even they did not show the
>> symptom, to keep codes as consistent for x86 arch.
>>
>>    Thanks
>>    Yumin
>>
>> On 7/9/2013 3:11 PM, Yumin Qi wrote:
>>> Vladimir,
>>>
>>> On 7/9/2013 2:16 PM, Vladimir Kozlov wrote:
>>>> Hi Yumin,
>>>>
>>>> load_acquire() could be more expensive with this changes even for
>>>> 64bit VM because you first loading from volatile address into local
>>>> variable. Please, check what code is generated in 64-bit with your
>>>> changes
>>> I will check for that. Or we can guard by AMD64.
>>>> Why you did not use release_store_fence() in
>>>> OrderAccess::release_store_fence() and where is cast to jlong* ?
>>>>
>>> You  are right,  it is better with release_store_fence() on 64bit.
>>> There is no functions for casting pointer I think.
>>>
>>> Thanks
>>> Yumin
>>>> Thanks,
>>>> Vladimir
>>>>
>>>> On 7/9/13 11:32 AM, Yumin Qi wrote:
>>>>> Hi,
>>>>>
>>>>>    Can i have your codereview of this change:
>>>>>    Unsafe_Get[SET]DoubleVolatile are not atomic on 32bit x86 linux
>>>>> caused test for
>>>>> org.openjdk.concurrent.torture.tests.atomicity.primitives.reflect.DoubleAtomicityTest 
>>>>>
>>>>>
>>>>> failed.
>>>>>    The fix is using same treatment for jdouble as for jlong. Tests
>>>>> passed on failed test case, vm quick tests. It only happens on linux
>>>>> 32bit platform, on solaris, the inlined code be compiled into code of
>>>>> using fldl/fstpl which are atomic instructions.
>>>>>
>>>>>    Contributed by: dholmes
>>>>>
>>>>>    URL: http://cr.openjdk.java.net/~minqi/8016538/01
>>>>>
>>>>>    Thanks
>>>>>    Yumin
>>>
>>