[OpenJDK 2D-Dev] [10] RFR: JDK-8188083- NPE in java.awt.image.FilteredImageSource.startProduction

Sergey Bylokhov Sergey.Bylokhov at oracle.com
Fri Oct 27 04:50:57 UTC 2017


One more note:
I guess it is possible to create a stable test like below which can 
reproduce the bug:

import java.awt.image.ColorModel;
import java.awt.image.FilteredImageSource;
import java.awt.image.ImageConsumer;
import java.awt.image.ImageFilter;
import java.awt.image.ImageProducer;
import java.util.Hashtable;

public final class Test {

     private volatile static Throwable fail;

     public static void main(final String[] args) throws 
InterruptedException {
         final ImageConsumer ic = new ImageConsumer() {
             @Override
             public void setDimensions(int i, int i1) {
             }

             @Override
             public void setProperties(Hashtable<?, ?> hashtable) {
             }

             @Override
             public void setColorModel(ColorModel colorModel) {
             }

             @Override
             public void setHints(int i) {
             }

             @Override
             public void setPixels(int i, int i1, int i2, int i3,
                                   ColorModel colorModel, byte[] bytes, 
int i4,
                                   int i5) {
             }

             @Override
             public void setPixels(int i, int i1, int i2, int i3,
                                   ColorModel colorModel, int[] ints, 
int i4,
                                   int i5) {
             }

             @Override
             public void imageComplete(int i) {
             }
         };
         final ImageProducer ip = new ImageProducer() {
             @Override
             public void addConsumer(ImageConsumer imageConsumer) {
             }

             @Override
             public boolean isConsumer(ImageConsumer imageConsumer) {
                 return false;
             }

             @Override
             public void removeConsumer(ImageConsumer imageConsumer) {
             }

             @Override
             public void startProduction(ImageConsumer imageConsumer) {
             }

             @Override
             public void requestTopDownLeftRightResend(
                     ImageConsumer imageConsumer) {
             }
         };

         ImageFilter filter = new ImageFilter();
         FilteredImageSource fis = new FilteredImageSource(ip, filter);
         Thread t1 = new Thread(() -> {
             try {
                 while (true) {
                     fis.addConsumer(ic);
                 }
             } catch (Throwable t) {
                 fail = t;
             }
         });
         Thread t2 = new Thread(() -> {
             try {
                 while (true) {
                     fis.removeConsumer(ic);
                 }
             } catch (Throwable t) {
                 fail = t;
             }
         });
         Thread t3 = new Thread(() -> {
             try {
                 while (true) {
                     fis.startProduction(ic);
                 }
             } catch (Throwable t) {
                 fail = t;
             }
         });
         t1.setDaemon(true);
         t2.setDaemon(true);
         t3.setDaemon(true);

         t1.start();
         t2.start();
         t3.start();

         t1.join(10000);
         if (fail != null) {
             throw new RuntimeException("Test fail", fail);
         }
     }
}

On 25/10/2017 23:58, Prahalad Kumar Narayanan wrote:
> Hello Sergey
> 
> Thank you for the suggestion.
> 
> I 've updated JBS with below information.
>     1 . Stack trace information as provided by submitter-
>          java.lang.NullPointerException
>              at java.awt.image.FilteredImageSource.startProduction(FilteredImageSource.java:181)
>              at java.awt.image.FilteredImageSource.startProduction(FilteredImageSource.java:183)
>              at sun.awt.image.ImageRepresentation.startProduction(ImageRepresentation.java:732)
>              at sun.awt.image.ToolkitImage.addWatcher(ToolkitImage.java:221)
>      2. Screenshot showing the occurrence of the exception at FilteredImageSource.java: 181.
>              . The image also shows the test passing with JDK10 containing the fix on VM running Linux Ubuntu x64.
> 
> Thank you
> Have a good day
> 
> Prahalad N.
> 
> -----Original Message-----
> From: Sergey Bylokhov
> Sent: Thursday, October 26, 2017 12:05 PM
> To: Prahalad Kumar Narayanan; 2d-dev
> Subject: Re: [OpenJDK 2D-Dev] [10] RFR: JDK-8188083- NPE in java.awt.image.FilteredImageSource.startProduction
> 
> Hi, Prahalad.
> 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.
> 


-- 
Best regards, Sergey.


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