8330748: ByteArrayOutputStream.writeTo(OutputStream) pins carrier

[bplb]

Prevent blocking due to a carrier thread not being released when ByteArrayOutputStream.writeTo is invoked from a virtual thread.

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Issue

• JDK-8330748: ByteArrayOutputStream.writeTo(OutputStream) pins carrier (Enhancement - P4)

Reviewers

• Alan Bateman (@AlanBateman - Reviewer)

Reviewing

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8330748: ByteArrayOutputStream.writeTo(OutputStream) pins carrier

Reviewed-by: alanb

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[mlbridge]

Webrevs

• 03: Full - Incremental (8076291f)
• 02: Full - Incremental (1dd59b7b)
• 01: Full - Incremental (57e4917b)
• 00: Full (08bb9cb6)

[bplb]

Tiers 1-3 passed on the usual platforms.

[AlanBateman]

As a temporary workaround then I think this is okay. It does mean there needs to a heap space for the snapshot. Aside from that, the behavioral difference should only be observable to something that is relying on unspecified behavior. BAOS does not document anything about thread safety or that its methods are synchronized.

[viktorklang-ora]

Has the alternative of moving to a j.u.c.Lock (Needs Reentrant or not?) been explored/benchmarked?

[AlanBateman]

Has the alternative of moving to a j.u.c.Lock (Needs Reentrant or not?) been explored/benchmarked?

Yes, decided not to do because it's just guarding access to a byte[] and any changes can influence the inlining. Plus, it would need to continue to use monitors when extended as the subclass may assume synchronization in the super class. Limiting it to just the problematic writeTo method seem the least risky.

[viktorklang-ora]

Has the alternative of moving to a j.u.c.Lock (Needs Reentrant or not?) been explored/benchmarked?

Yes, decided not to do because it's just guarding access to a byte[] and any changes can influence the inlining. Plus, it would need to continue to use monitors when extended as the subclass may assume synchronization in the super class. Limiting it to just the problematic writeTo method seem the least risky.

That's true, good points across the board.

[AlanBateman]

Updated version looks fine.

[bplb]

Running tests now. Assuming those pan out, will likely integrate tomorrow.

[bplb]

/integrate

[openjdk]

Going to push as commit 819f3d6.
Since your change was applied there have been 61 commits pushed to the master branch:

• eb88343: 8331164: createJMHBundle.sh download jars fail when url needed to be redirected
• 9b423a8: 8330253: Remove verify_consistent_lock_order
• 4e42294: 8329004: Update Libpng to 1.6.43
• bdcc240: 8331087: Move immutable nmethod data from CodeCache
• 8b8fb64: 8324776: runtime/os/TestTransparentHugePageUsage.java fails with The usage of THP is not enough
• 151ef5d: 8330677: Add Per-Compilation memory usage to JFR
• 7272939: 8331200: Serial: Remove unused methods in SerialHeap
• 70d3f22: 8331175: Parallel: Remove VerifyRememberedSets
• 549bc6a: 8330685: ZGC: share barrier spilling logic
• 76cda7b: 8331118: Remove Serial includes from space.hpp
• ... and 51 more: https://git.openjdk.org/jdk/compare/f1d0e715b67e2ca47b525069d8153abbb33f75b9...master

Your commit was automatically rebased without conflicts.

[openjdk]

@bplb Pushed as commit 819f3d6.

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