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

[Bengt Rutisson]

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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