[OpenJDK 2D-Dev] bug 8146238 - Java Queue Flusher on MacOS

[Alexey Ushakov]

Hi Sergey,

The proposed solution looks good for me.

Best Regards,
Alexey


> On 12 Aug 2019, at 12:29, Sergey Bylokhov <Sergey.Bylokhov at oracle.com> wrote:
> 
> Hi, Phil, Alexey.
> 
> I recheck this bug, and here is some of my thought:
> 1. We have two java classes:
>    - GLX/CGL/WGL/GraphicsConfig which maintain the native structure WGL/GLX/CGL/GraphicsConfigInfo
>    - GLX/CGL/WGL/SurfaceData which maintain the native structure CGL/GLXS/WGL/SDOps
> 2. The native structures should be disposed of by the "Disposer" machinery
> 3. The native part XXXSDOps has a pointer to the CGL/GraphicsConfigInfo
> 4. To prevent the usage of dangling pointer to the XXXGraphicsConfigInfo, the java part of XXXSDOps has a strong reference to the java part of XXXGraphicsConfigInfo
> 
> The assumption at point 4 is not correct, it is possible that the native part of the XXXGraphicsConfigInfo could be disposed before XXXSDOps, and we will get a crash when we will try to dispose the XXXSDOps.
> 
> Long time ago when it was implemented it works fine, because we never dispose the graphics configs, we read them on-start and use till the end of the application, even now we use this approach on Linux(JDK-8076313).
> 
> So this bug existed on Linux, Windows and migrated to the macOS platform, but only on macOS and windows we can get a crash.
> 
> 
> I have rechecked the usage of the pointer from XXXSDOps to XXXGraphicsConfigInfo which caused a crash and think that we can get rid it, but it will required to change bunch of code on all platforms, so as a minimal fix I suggest this one:
> http://cr.openjdk.java.net/~serb/8146238/webrev.00
> Just to store the reference to the GC till the moment it will not be used by the SurfaceData.
> 
> 
> On 8/7/19 10:56 am, Phil Race wrote:
>> Sergey,
>> This fix seems OK to me. Can you please do whatever re-evaluation you meant
>> as I'd like to pull it into jdk/client for Alexey (since he does not have current commit rights).
>> -phil.
>> On 3/8/18 2:59 PM, Sergey Bylokhov wrote:
>>> Hi, Bill.
>>> Thank you for confirmation.
>>> 
>>> On 08/03/2018 14:08, Bill York wrote:
>>>> 3. Is there a plan to get this bug fix into the JRE distributed by Oracle?
>>> 
>>> I will reevaluate the fix for inclusion in jdk11.
>>> 
>>> 
> 
> 
> -- 
> Best regards, Sergey.