A Bug about the JVM Attach mechanism

[Yasumasa Suenaga]

Hi,

Can we fix this issue like this webrev?
   http://cr.openjdk.java.net/~ysuenaga/JDK-8225690/proposal/

I could reproduce this issue with ConcAttachTest.java in it
on my laptop.
(Fedora 30 x64 on Hyper-V guest: Core i3-8145U x 2vcpu)

If we need to fix based on current implementation, I think
we need to use atomic operation.
But if we can refactor around here, we might be able to another approach 
- e.g. using monitors/mutexes


Thanks,

Yasumasa


On 2019/06/21 5:49, David Holmes wrote:
> Sorry it took me a while to understand the specifics of the problem. :)
> 
> David
> 
> On 20/06/2019 3:37 am, nijiaben wrote:
>> Yes Alan, I mean this
>> ------------------?Original?------------------
>> *From: *?"Alan Bateman"<Alan.Bateman at oracle.com>;
>> *Date: *?Thu, Jun 20, 2019 02:54 PM
>> *To: *?"nijiaben"<nijiaben at perfma.com>; "David
>> Holmes"<david.holmes at oracle.com>;
>> "serviceability-dev"<serviceability-dev at openjdk.java.net>;
>> "jdk8u-dev"<jdk8u-dev at openjdk.java.net>;
>> "hotspot-runtime-dev"<hotspot-runtime-dev at openjdk.java.net>;
>> *Subject: *?Re: A Bug about the JVM Attach mechanism
>> On 20/06/2019 05:10, nijiaben wrote:
>>   > :
>>   > I know this mechanism, can we provide means of recovery to avoid
>> unavailability caused by accidental deletion?
>>   >
>> Are you concerned about tmpreaper or cron jobs that periodically cleanup
>> /tmp? There may indeed be an issue for applications that run for weeks
>> or months. If someone is using jmap, jcmd or other tools using the
>> attach API then it will trigger the attach listener to start. When they
>> come back in a few weeks then the .java_pid<pid> file may have been
>> removed so they cannot attach. Is this what what you are pointing out?
>>
>> -Alan