RFR 7122142 : (ann) Race condition between isAnnotationPresent and getAnnotations

[Peter Levart]

Thank you Joel, Alan, David and Aleksey for reviews.

Regards, Peter

On 07/15/2013 02:30 PM, Joel Borggrén-Franck wrote:
> Thanks for the review David,
>
> I have pushed version 5 of the patch.
>
> cheers
> /Joel
>
> On 2013-07-15, David Holmes wrote:
>> Joel, Peter,
>>
>> I've looked at the synchronization changes and the use of CAS and it
>> seems sound.
>>
>> The only performance-related concern is the wasted effort when
>> multiple threads each call "new AnnotationType(annotationClass)".
>> But if that turns out to be an issue we can address it (using
>> memoization pattern that installs a Future for the AnnotationType).
>>
>> Thanks,
>> David
>>
>>>> *From: *Peter Levart <peter.levart at gmail.com
>>>> <mailto:peter.levart at gmail.com>>
>>>> *Subject: **RFR 7122142 : (ann) Race condition between
>>>> isAnnotationPresent and getAnnotations*
>>>> *Date: *8 juli 2013 22:54:12 CEST
>>>> *To: *Joel Borggrén-Franck <joel.franck at oracle.com
>>>> <mailto:joel.franck at oracle.com>>
>>>> *Cc: *Alan Bateman <Alan.Bateman at oracle.com
>>>> <mailto:Alan.Bateman at oracle.com>>, "core-libs-dev at openjdk.java.net
>>>> <mailto:core-libs-dev at openjdk.java.net> core-libs-dev"
>>>> <core-libs-dev at openjdk.java.net <mailto:core-libs-dev at openjdk.java.net>>
>>>>
>>>> Helo,
>>>>
>>>> I need a Reviewer for the following patch:
>>>>
>>>> http://cr.openjdk.java.net/~plevart/jdk8-tl/AnnotationType/webrev.05/
>>>>
>>>> This fixes deadlock situation described in bug:
>>>>
>>>> http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=7122142
>>>>
>>>> The in-depth evaluation of the patch is described in the introductory
>>>> message of this thread:
>>>>
>>>> http://mail.openjdk.java.net/pipermail/core-libs-dev/2013-June/018226.html
>>>>
>>>> The above is the 5th revision of the patch that also makes sure a
>>>> single AnnotationType instance is ever returned for the same Class
>>>> object even when multiple threads concurrently request one.
>>>>
>>>>
>>>> Regards, Peter
>>>>
>>>> On 07/05/2013 04:04 PM, Joel Borggrén-Franck wrote:
>>>>> Hi Peter,
>>>>>
>>>>> Thanks for the quick update!
>>>>>
>>>>> While I have looked over the changes to j.l.Class and the cas in AnnotationType I don't think I'm qualified to review that. (FWIW it looked fine to me but my jmm isn't swapped in at the moment so I won't pretend to know the interactions between volatile and Unsafe cas). Thinking out loud I suppose we can assume a stable offset of fields in Class, and I realize that part has been under review before.
>>>>>
>>>>> The rest of AnnotationType, AnnotationParser and the tests look fine though. I also ran the tests before and after the change and results were as expected.
>>>>>
>>>>> Since I'm not a Reviewer kind of reviewer you need to get one those to sign off but after that I think you are good to go. I can sponsor this as well if Alan is busy.
>>>>>
>>>>> cheers
>>>>> /Joel
>>>>>
>>>>> On 5 jul 2013, at 11:12, Peter Levart<peter.levart at gmail.com>  wrote:
>>>>>
>>>>>> Hi Again,
>>>>>>
>>>>>> Sorry, the 4th revision I posted is not rebased to the current tip of jdk8-tl so it contained some diffs that reverted some things.
>>>>>>
>>>>>> Here's the correct patch:
>>>>>>
>>>>>> http://cr.openjdk.java.net/~plevart/jdk8-tl/AnnotationType/webrev.05/
>>>>>>
>>>>>>
>>>>>> Regards, Peter
>>>>>>
>>>>>>
>>>>>> On 07/05/2013 10:32 AM, Peter Levart wrote:
>>>>>>> Hi Joel,
>>>>>>>
>>>>>>> Here's the 4th revision of the patch:
>>>>>>>
>>>>>>> http://cr.openjdk.java.net/~plevart/jdk8-tl/AnnotationType/webrev.04/
>>>>>>>
>>>>>>> This one introduces CAS-ing of the AnnotationType instance into the Class.annotationType field so that there's only a single instance ever returned for a single Class. I also introduced new private static Class.Atomic nested class that is used to lazily initialize Unsafe machinery and to provide a safe wrapper for internal j.l.Class use. Previously this was part of ReflectionData nested class because it was only used for it's purpose. In anticipation to have a need for more atomic operations in the future, I moved this code to a separate class. ReflectionData is now just a record.
>>>>>>>
>>>>>>> Regards, Peter