Request for review 6840152: JVM crashes when heavyweight monitors are used

[David Holmes]

Coleen Phillimore said the following on 02/17/11 01:47:
> On 2/16/2011 1:33 AM, David Holmes wrote:
>>
>> I don't see a UseHeavyWeightMonitors flag in the current source. And 
>> the change in arguments.cpp refers to both UseHeavyMonitors and 
>> UseFastLocking, so I'm confused about this "renaming".
>>
>> And I'm not sure this warning logic is quite right:
>>
>> +   // Turn off biased locking for locking debug mode flags
>> +   if (!UseFastLocking || UseHeavyMonitors) {
>> +     if (!FLAG_IS_DEFAULT(UseBiasedLocking)) {
>> +       warning("Biased Locking is not supported with locking debug 
>> flags");
>> +     }
>> +     UseBiasedLocking = false;
>> +   }
>>
>> These FLAG macros always confuse me but surely the issue is whether 
>> UseBiasedLocking is true, not whether it has its "default value" ???
>>
>> On some architectures the default value of UseBiasedLocking is false.
> 
> You are right.  The FLAG_IS_DEFAULT is if someone specified it on the 
> command line, but I should also check if they specified it to be true.

That's the bit that always confuses me, it doesn't mean "flag currently 
has the same value as its default", but rather "flag has not been set 
explicitly".

Anyway all clear now and putback is good.

Thanks,
David

> The earlier description was replaced with:
> Summary: Turn off biased locking if !UseFastLocking or UseHeavyMonitors 
> options are requested.
> 
> 
> Thanks,
> Coleen
> 
>>
>> David
>>
>>
>> Coleen Phillimore said the following on 02/16/11 05:19:
>>> Summary: Renamed UseHeavyWeightMonitors flag to !UseFastLocking flag 
>>> and turn off biased locking if !UseFastLocking option is requested.
>>>
>>> open webrev at http://cr.openjdk.java.net/~coleenp/6840152/
>>> bug link at http://bugs.sun.com/view_bug.do?bug_id=6840152
>>>
>>> Tested against specjbb2005.
>>>
>>> Thanks,
>>> Coleen
>>>
>