RFR 8201799: Build failures after JDK-8195099 (Concurrent safe-memory-reclamation mechanism)

[Erik Österlund]

Hi,

Please also note that the Atomic::add used in write_synchronize assumes 
bidirectional fencing (which is the contract provided by Atomic::add). 
This is however not true for the PPC backend of Atomic::add - it has 
acq_rel semantics instead. So this mechanism is currently not safe to 
use on PPC.

 From globalCounter.cpp:
   61   // Atomic::add must provide fence since we have storeload 
dependency.
   62   volatile uintx gbl_cnt = Atomic::add((uintx)COUNTER_INCREMENT, 
&_global_counter._counter);

Might want to have a look at the safe use of this mechanism on PPC as a 
follow-up.

Thanks,
/Erik

On 2018-04-18 14:27, David Holmes wrote:
> Hi Aleksey,
>
> On 18/04/2018 9:50 PM, Aleksey Shipilev wrote:
>> Bug:
>>    https://bugs.openjdk.java.net/browse/JDK-8201799
>>
>> Fix:
>>
>> diff -r bfba4712d4ff 
>> src/hotspot/share/utilities/globalCounter.inline.hpp
>> --- a/src/hotspot/share/utilities/globalCounter.inline.hpp Wed Apr 18 
>> 11:36:48 2018 +0200
>> +++ b/src/hotspot/share/utilities/globalCounter.inline.hpp Wed Apr 18 
>> 13:50:34 2018 +0200
>> @@ -27,6 +27,7 @@
>>
>>   #include "runtime/orderAccess.inline.hpp"
>>   #include "runtime/thread.hpp"
>
> The above line can be deleted now.
>
>> +#include "runtime/thread.inline.hpp"
>
> Fix is good.
>
> Thanks,
> David
>
>>   #include "utilities/globalCounter.hpp"
>>
>>   inline void GlobalCounter::critical_section_begin(Thread *thread) {
>>
>> Testing: failing aarch64 build
>>
>> Thanks,
>> -Aleksey
>>