[OpenJDK 2D-Dev]  RFR: JDK-8188083- NPE in java.awt.image.FilteredImageSource.startProduction
Sergey.Bylokhov at oracle.com
Thu Oct 26 06:34:35 UTC 2017
Can you please add a stack trace which include a line numbers to the bug
report? Currently it is unclear in what line an exception is occurred.
On 25/10/2017 21:07, Prahalad Kumar Narayanan wrote:
> Hello Everyone
> Good day to you.
> Kindly review a fix for the bug
> Bug ID: JDK-8188083
> Description: Null Pointer Exception in java.awt.image.FilteredImageSource.startProduction
> Root Cause
> . FilteredImageSource implements ImageProducer interface
> . All the methods of FilteredImageSource operate on a common data -HashTable, but only a few are synchronized methods.
> . Thus, when synchronized & un-synchronized methods access / modify the hash table in a multi-threaded scenario, it renders the class vulnerable to this exception.
> Exception occurrence
> . The submitter has mentioned that there is no test-case to reproduce to this issue.
> . Luckily I was able to observe this issue with a "crude" test code
> . The test triggered 7k threads in an ExecutorService randomly adding/ removing/ invoking startProduction on FilteredImageSource object.
> . I didn't feel it robust enough to be added as a part of regression tests. I tried optimizing the test but in vain.
> . Hence the test code isn't added to the webrev.
> Details on the Fix:
> . The concerned methods have been "synchronized" in the fix.
> . No new regression failures were observed with this change.
> Kindly review the change and provide your feedback.
> In addition, kindly suggest whether this requires CSR as it adds "synchronized" to method signature.
> Review Link: http://cr.openjdk.java.net/~pnarayanan/8188083/webrev.00/
> Thank you for your time in review
> Have a good day
> Prahalad N.
Best regards, Sergey.
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