RFR(xxs): 8213236: A partial removed/deleted JavaThread cannot transition

[David Holmes]

+2 :)

Thanks,
David

PS. Thanks Dan for explaining the issue in the bug report!

On 2/11/2018 5:31 AM, Erik Osterlund wrote:
> +1
> 
> /Erik
> 
>> On 1 Nov 2018, at 20:22, Robbin Ehn <robbin.ehn at oracle.com> wrote:
>>
>> Hi Dan,
>>>> I don't think we should grab Heap_lock at all and we should just remove it.
>>>> If there is a problem with "unparseable heap", taking Heap_lock seems to the wrong solution.
>>> I don't think you want to drob the grab of the Heap_lock from
>>> this code path as part of this fix. That should be done separately.
>>> Of course, you have GC folks close to you so you might be able to
>>> resolve the issue (theoretically) quickly. However, I think that
>>> will mean that this fix needs more testing.
>>
>> I was wrong, we can do as you say just skip safepoint checks on Heap_lock.
>>
>> The incremental is:
>> diff -r f5f6ed30bb13 src/hotspot/share/runtime/thread.cpp
>> --- a/src/hotspot/share/runtime/thread.cpp    Thu Nov 01 20:10:18 2018 +0100
>> +++ b/src/hotspot/share/runtime/thread.cpp    Thu Nov 01 20:17:58 2018 +0100
>> @@ -4289,1 +4289,1 @@
>> -    MutexLocker ml(Heap_lock);
>> +    MutexLockerEx ml(Heap_lock, Mutex::_no_safepoint_check_flag);
>> diff -r f5f6ed30bb13 src/hotspot/share/runtime/vmThread.cpp
>> --- a/src/hotspot/share/runtime/vmThread.cpp    Thu Nov 01 20:10:18 2018 +0100
>> +++ b/src/hotspot/share/runtime/vmThread.cpp    Thu Nov 01 20:17:58 2018 +0100
>> @@ -323,1 +323,1 @@
>> -  assert(((JavaThread*)Thread::current())->is_terminated(), "Should be off threadslist");
>> +  assert(((JavaThread*)Thread::current())->is_terminated(), "Should be terminated");
>>
>> Re-running t1-2, I expect no problems.
>>
>> Thanks!
>>
>> /Robbin
>>
>>> Dan
>>>>
>>>> /Robbin
>>>>
>>>>>
>>>>> Dan
>>>>>
>>>>>
>>>>>
>>>>>> _should_terminate = true;
>>>>>>       VMOperationQueue_lock->notify();
>>>>>>     }
>>>>>>
>>>>>> Passes t1-2.
>>>>>>
>>>>>> Thanks Robbin
>>>>>
>