[OpenJDK 2D-Dev] RFR: 8263138: Initialization of sun.font.SunFontManager.platformFontMap is not thread safe

[Sergey Bylokhov]

On Sun, 28 Feb 2021 03:50:13 GMT, liach <github.com+7806504+liach at openjdk.org> wrote:

>> src/java.desktop/share/classes/sun/font/SunFontManager.java line 1452:
>> 
>>> 1450:         if (platformFontMap == null) {
>>> 1451:             platformFontMap = populateHardcodedFileNameMap();
>>> 1452:             SunFontManager.platformFontMap = platformFontMap;
>> 
>> I am not sure it is enough for "thread-safe initialization". The "platformFontMap" might not be null, but its content can be broken/incomplete at this point.
>
> https://github.com/openjdk/jdk/pull/2691#issuecomment-784367127
> 
> In short, previously platformFontMap references were field set/gets and may be inconsistent due to concurrency. It is now moved to a local variable; also the map modifications have been moved to fields to avoid concurrency issues with hash map as far as I can see.

One thread may create the local platformFontMap, then set the static SunFontManager.platformFontMap field, and then initialize the platformFontMap or mix these operations. The second thread may see non-null SunFontManager.platformFontMap which is not still initialized.

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PR: https://git.openjdk.java.net/jdk/pull/2762