8355078: java.awt.Color.createContext() uses unnecessary synchronization

[mrserb]

At some point, java.awt.Color.createContext() was marked as synchronized to support caching of a ColorPaintContext instance. The cache was later removed, but the synchronized modifier remained. Since there is no shared mutable state anymore, the synchronization is no longer necessary and can be safely removed.

Note: This code path is rarely executed because a special optimization was introduced in SunGraphics2D.setPaint. As a result, unless a custom wrapper around the Color class is used, the Color.createContext() method is typically bypassed during rendering.

Two tests are added:

• ColorPaintContextBasicTest: Checks if different image types (BufferedImage and VolatileImage) produce the same results when using different ways to fill the image (setColor, setPaint, and custom Paint). This test intentionally uses a custom Paint implementation to bypass the optimization and ensure that Color.createContext() is invoked verifying its correct behavior.
• ColorPaintContextStateTrackerTest: Checks that the raster used in ColorPaintContext.getRaster() can be properly cached in video memory and we do not need to call icr.markDirty() in ColorPaintContext.getRaster()

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Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
• Change must not contain extraneous whitespace
• Commit message must refer to an issue
• Change requires CSR request JDK-8356113 to be approved

Issues

• JDK-8355078: java.awt.Color.createContext() uses unnecessary synchronization (Bug - P5)
• JDK-8356113: java.awt.Color.createContext() uses unnecessary synchronization (CSR)

Reviewers

• Phil Race (@prrace - Reviewer)

Reviewing

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[bridgekeeper]

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[mrserb]

/csr

[openjdk]

@mrserb This change now passes all automated pre-integration checks.

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After integration, the commit message for the final commit will be:

8355078: java.awt.Color.createContext() uses unnecessary synchronization

Reviewed-by: prr

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[openjdk]

@mrserb has indicated that a compatibility and specification (CSR) request is needed for this pull request.

@mrserb please create a CSR request for issue JDK-8355078 with the correct fix version. This pull request cannot be integrated until the CSR request is approved.

[openjdk]

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[liach]

Is a CSR requested for the access flags change? Some method flags, notably native or synchronized, are not part of the API specificaion and not rendered, and thus can be changed without CSR reviews. For example, the javadoc for this particular method does not include the synchronized modifier.

[mrserb]

Since ColorPaintContext is no longer cached within the Color class, it's unlikely that this object will be accessed by multiple threads in typical JDK usage. Therefore, the synchronized modifier has been removed from the getRaster() method. However, to ensure thread safety in the rare case where a ColorPaintContext instance is shared across threads (if app decides to do so for some reason), the savedTile field has been declared as volatile.

[mlbridge]

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[mrserb]

/integrate

[openjdk]

Going to push as commit 890456f.
Since your change was applied there have been 24 commits pushed to the master branch:

• 637e9d1: 8354556: Expand value-based class warnings to java.lang.ref API
• fbeea1d: 8356844: Missing @serial annotation for sun.print.CustomOutputBin#serialVersionUID
• 27a4243: 8354560: Exponentially delay subsequent native thread creation in case of EAGAIN
• ... and 21 more: https://git.openjdk.org/jdk/compare/6c42856b8d5039c14ba04a48c60d09039d5030fe...master

Your commit was automatically rebased without conflicts.

[openjdk]

@mrserb Pushed as commit 890456f.

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