[OpenJDK 2D-Dev] [14] Review Request: 8229810 NullPointerException getting bounds of GraphicsConfiguration

[Sergey Bylokhov]

Any volunteers to review=)?

On 8/19/19 12:03 pm, Sergey Bylokhov wrote:
> Hello.
> Please review the fix for JDK 14.
> 
> Bug: https://bugs.openjdk.java.net/browse/JDK-8229810
> Fix: http://cr.openjdk.java.net/~serb/8229810/webrev.00
> 
> The root cause is a lack of synchronization in CGraphicsEnvironment,
> we create the GraphicsDevice under a special lock which is used to
> access the list of devices:
> http://hg.openjdk.java.net/jdk/client/file/39f133168348/src/java.desktop/macosx/classes/sun/awt/CGraphicsEnvironment.java#l184
> 
> but initialize the device w/o this lock.
> http://hg.openjdk.java.net/jdk/client/file/39f133168348/src/java.desktop/macosx/classes/sun/awt/CGraphicsEnvironment.java#l187
> 
> So it is possible that we create the device, add it to the list of devices,
> and before we initialize it the user could access the not fully initialized object.
> 
> The bug exists from the jdk7, but it was hidden because all fields in CGraphicsDevice
> were primitives, so the app just used invalid data. In JDK-8211992 the object field "bounds"
> was added and now we can get NPE if this field was not initialized.
> 
> As a fix, I suggest to always initialize the graphics device in the constructor.
> 
> Note that we cannot move "displayChanged" which will notify devices and all listeners
> in awt/swing in the CGraphicsEnvironment under the lock, it will cause various
> deadlocks in the a different listeners.
> 


-- 
Best regards, Sergey.