RFR: JDK-8155730: HeapInfoDCmd should get Heap_lock

[Yasumasa Suenaga]

Hi David,

> Taking locks during VMError handling is problematic - we're executing from a signal handler and the VM is crashing. Much of what we do from VMError is "best effort".

I will remove MutexLocker from VMError::report().
But I added assert_locked_or_safepoint(Heap_lock) in each CollectedHeap.
If we remove Heap_lock from VMError::report(), fastdebug HotSpot is failed
when it prints heap info to hs_err log.
Should I remove assert_locked_or_safepoint()?

VMError::print_vm_info() calls from VMInfoDCmd::execute() only.
So I think we should take Heap_lock at this function.
Or should we take Heap_lock at VMInfoDCmd::execute() ?


Thanks,

Yasumasa


On 2016/05/09 21:26, David Holmes wrote:
> On 9/05/2016 10:20 PM, Yasumasa Suenaga wrote:
>> Hi all,
>>
>> I've sent review request for JDK-8155730.
>> However, I found caller of Universe::heap()->print_*() in vmError.cpp .
>> Thus I added MutexLocker(Ex) for Heap_lock to VMError::report() and
>> VMError::print_vm_info().
>
> Taking locks during VMError handling is problematic - we're executing from a signal handler and the VM is crashing. Much of what we do from VMError is "best effort".
>
> David
>
>> Could you review again?
>>
>>   http://cr.openjdk.java.net/~ysuenaga/JDK-8155730/webrev.01/
>>
>>
>>> This needs to be reviewed by the GC folk not runtime. Please direct
>>> followups to hotspot-gc-dev.
>>
>> Thanks, David!
>>
>>
>> Yasumasa
>>
>>
>> On 2016/05/06 13:11, David Holmes wrote:
>>> Hi Yasumasa,
>>>
>>> This needs to be reviewed by the GC folk not runtime. Please direct
>>> followups to hotspot-gc-dev.
>>>
>>> Thanks,
>>> David
>>>
>>> On 30/04/2016 12:05 AM, Yasumasa Suenaga wrote:
>>>> Hi all,
>>>>
>>>> This review request is related to [1].
>>>>
>>>> HeapInfoDCmd calls CollectedHeap::print_on().
>>>> However, its call does not get Heap_lock.
>>>>
>>>> Heap_lock should be gotten from all heap operations.
>>>>
>>>> I uploaded webrev for this issue.
>>>> Could you review it?
>>>>
>>>>   http://cr.openjdk.java.net/~ysuenaga/JDK-8155730/webrev.00/
>>>>
>>>> I cannot access JPRT.
>>>> So I need a sponsor.
>>>>
>>>>
>>>> Thanks,
>>>>
>>>> Yasumasa
>>>>
>>>>
>>>> [1]
>>>> http://mail.openjdk.java.net/pipermail/hotspot-runtime-dev/2016-April/019257.html
>>>>
>>>>
>>>>