Review request (S): 7131791 G1: Asserts in nightly testing due to 6976060

[Bengt Rutisson]

Here is an updated webrev with the added assert:
http://cr.openjdk.java.net/~brutisso/7131791/webrev.05

Bengt

On 2012-01-20 17:56, Bengt Rutisson wrote:
>
> Stefan, are you OK with adding the assert that Tony suggested?
>
> Bengt
>
> On 2012-01-20 17:44, Stefan Karlsson wrote:
>> On 2012-01-20 17:46, Bengt Rutisson wrote:
>>>
>>> Stefan,
>>>
>>> Thanks for the prompt review!
>>>
>>> Comments inline.
>>>
>>> On 2012-01-20 17:21, Stefan Karlsson wrote:
>>>> On 20 jan 2012, at 17:06, Bengt Rutisson <bengt.rutisson at oracle.com 
>>>> <mailto:bengt.rutisson at oracle.com>> wrote:
>>>>
>>>>>
>>>>> Hi all,
>>>>>
>>>>> Can I have a couple of quick reviews for this small change:
>>>>> http://cr.openjdk.java.net/~brutisso/7131791/webrev.02 
>>>>> <http://cr.openjdk.java.net/%7Ebrutisso/7131791/webrev.02>
>>>>>
>>>>> This should hopefully fix the 500+ failures in the G1 nightlies. 
>>>>> So, I would like to get it in before the nightlies tonight.
>>>>>
>>>>> The issue is that we call collect() which will trigger a 
>>>>> collection without protecting the memory that we just allocated 
>>>>> for a humongous object. The fix (thanks Tony for helping me 
>>>>> out!!!) is to fake an object and create a handle to it before we 
>>>>> call collect.
>>>>
>>>> 1067         Handle h((oop)result);  
>>>> 1068         collect(GCCause::_g1_humongous_allocation);
>>>> 1069       }
>>>> 1070       return result;
>>>> 1071     }
>>>> Can we really have a handle to uninitialized memory?
>>>
>>> The memory is not uninitialized since I fake an object there with 
>>> the call to CollectedHeap::fill_with_object(result, word_size, 
>>> false); just before the code you have above.
>>
>> I missed that.
>>
>>>
>>>> Are you sure that the humongous object will not be moved by a full collection. You should probably return h() instead of result.
>>>
>>> Humongous objects will not be moved by G1 collections so I think we 
>>> are ok.
>>
>> OK. But maybe we should be a bit defensive and return h() here.
>>
>> StefanK
>>
>>>
>>> Thanks for the prompt review!
>>>
>>> Bengt
>>>>
>>>> StefanK
>>>>
>>>>>
>>>>> Bengt
>>>
>>
>

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