RFR: 8152955: Many safepoints of "no vm operation" kind

[Robbin Ehn]

Hi David, thanks for looking at this.

On 05/24/2017 06:07 AM, David Holmes wrote:
> Hi Robbin,
> 
> On 24/05/2017 4:32 AM, Robbin Ehn wrote:
>> Hi all, please review.
>>
>> When cleanup, safepointalot or vm halt starts a safepoint without an operation we now set a reason string for.
>>
>> Webrev: http://cr.openjdk.java.net/~rehn/8152955/
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8152955
> 
> This looks good. A couple of minor comments:
> 
> + bool VMThread::no_op_safepoint_needed(bool check_time) {
> +   _no_op_reason = "no operation"; // This value should never be printed
> 
> Not sure why you set "no operation". Harmless but ...

This was more a debug thing, removed. I also removed:
-const char*       VMThread::_no_op_reason       = "no operation";
+const char*       VMThread::_no_op_reason       = NULL;

> 
> 396     bool max_time_exceeded = GuaranteedSafepointInterval != 0 && (interval > GuaranteedSafepointInterval);
> 
> Can you split into two lines please.

Fixed

Thanks, Robbin

> 
> No need to see update, whatever you choose to do.
> 
> Thanks,
> David
> 
>> Passes hotspot_tier1
>>
>> Thanks, Robbin