Request for review (S): 7110718 -XX:MarkSweepAlwaysCompactCount=0 crashes the JVM

[Bengt Rutisson]

Hi all,

Here is an updated webrev. As John Cuthbertson suggested, I am now using 
verify_min_value(). That made the change really nice and small.

Changing MarkSweepAlwaysCompactCount to unsigned, as Jon suggested, 
turned out to be more involved than I would like. We use 
MarkSweepAlwaysCompactCount  together with IntFlagSetting. There is no 
UIntFlagSetting implementation, so I would either have to add that or 
cast the values back and forth to int and uint. Seems easier to leave 
the flag as int.

http://cr.openjdk.java.net/~brutisso/7110718/webrev.02/

Bengt


On 2011-11-15 15:46, Bengt Rutisson wrote:
>
> John,
>
> Thanks for the review!
>
> On 2011-11-14 21:19, John Cuthbertson wrote:
>> Hi Bengt,
>>
>> Why not use verify_min_value()?
>
> You are right. I'll change to using verify_min_value().
>
> Bengt
>
>
>>
>> JohnC
>>
>> On 11/14/11 01:25, Bengt Rutisson wrote:
>>>
>>> Hi all,
>>>
>>> Can I have a couple of reviews for this small change?
>>> http://cr.openjdk.java.net/~brutisso/7110718/webrev.01/
>>>
>>> It is a fix for the issue that Ramki reported recently. 
>>> MarkSweepAlwaysCompactCount is used for division and Hotspot crashes 
>>> if it is set to 0.
>>>
>>> I choose to log an error and exit the VM if someone tries to start 
>>> with -XX:MarkSweepAlwaysCompactCount=0. An alternative is to just 
>>> log a warning and set it to 1.
>>>
>>> I prefer the error way since it is not really clear what one wants 
>>> to achieve with MarkSweepAlwaysCompactCount=0. Always do full 
>>> compactions or never do full compactions? So I am not convinced that 
>>> 1 is an appropriate value.
>>>
>>> Also, since the VM, up until now, has crashed if someone tried 
>>> -XX:MarkSweepAlwaysCompactCount=0 I think we can be sure that there 
>>> are no customers that are running with that setting. It should be 
>>> safe to forbid it.
>>>
>>> CR:
>>>
>>> 7110718 -XX:MarkSweepAlwaysCompactCount=0 crashes the JVM
>>> http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=7110718
>>>
>>> Thanks,
>>> Bengt
>>
>