8295851: Do not use ttyLock in BytecodeTracer::trace

[coleenp]

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This didn't need ttyLock for synchronization, the code only needs to see if the method changes so it can print the method name before the bytecodes, like:

[490166] static void java.lang.String.() [490166] 13 18 putstatic 613 <java/lang/String.CASE_INSENSITIVE_ORDER:Ljava/util/Comparator;> [490166] 14 21 return

[490166] static void java.lang.System.() [490166] 15 0 invokestatic 471 <java/lang/System.registerNatives()V> [490166] 16 3 aconst_null [490166] 17 4 putstatic 474 <java/lang/System.in:Ljava/io/InputStream;>

Verified manually and added some parallelism to the test, and fixed trace() to initialize is_linked(), which it always is. Also ran tier1-4.

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Issue

• JDK-8295851: Do not use ttyLock in BytecodeTracer::trace (Enhancement - P4)

Reviewers

• David Holmes (@dholmes-ora - Reviewer)

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8295851: Do not use ttyLock in BytecodeTracer::trace

Reviewed-by: dholmes, matsaave

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At the time when this comment was updated there had been 121 new commits pushed to the master branch:

• 12196baf6700d00c244747cfa22767e532a4a963: 8358624: ImmutableDescriptor violates equals/hashCode contract after deserialization
• a471fe992fc0d71ba65b5fdbcc44b97a2783b90a: 8360539: DTLS handshakes fails due to improper cookie validation logic
• 839cede1a46b05d27abeaffbbd82c241910035cd: 8357289: Break down the String constructor into smaller methods
• ... and 118 more: https://git.openjdk.org/jdk/compare/49a82d880636a632f4a3471b14b1b1b29ce1d5e6...master

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[coleenp]

You could use a ThreadLocal for the current method being printed.

Oh yes that would be better, but I hate to add things to Thread for just one use. Actually, reprinting the method name probably helps with readability if multiple threads are interleaving output.

Thanks for the review @dholmes-ora

[dholmes-ora]

You could use a ThreadLocal for the current method being printed.

Oh yes that would be better, but I hate to add things to Thread for just one use.

No I literally meant a THREAD_LOCAL ie.

static THREAD_LOCAL Method* _method_currently_being_printed = nullptr;

[coleenp]

Oh yes, we don't use THREAD_LOCAL that much. I still think we want to repeat the method name if the threads become interweaved.

[coleenp]

Should the test also include the simple serial version?

Since we don't really verify the output, I don't think one would be needed. The test was originally added when there was a safepointing lock around BytecodeTracer in JDK 7 and the Method* moved, so all the test did was verify that tracing bytecodes didn't crash. With the concurrency I added, it did crash and found a bug that I fixed in BytecodeTracer::trace function.

[coleenp]

Thanks Matias and David for reviewing. /integrate

[openjdk[bot]]

Going to push as commit 4edf791aecd432ecde00652acfaabddf136f4ca7. Since your change was applied there have been 121 commits pushed to the master branch:

• 12196baf6700d00c244747cfa22767e532a4a963: 8358624: ImmutableDescriptor violates equals/hashCode contract after deserialization
• a471fe992fc0d71ba65b5fdbcc44b97a2783b90a: 8360539: DTLS handshakes fails due to improper cookie validation logic
• 839cede1a46b05d27abeaffbbd82c241910035cd: 8357289: Break down the String constructor into smaller methods
• ... and 118 more: https://git.openjdk.org/jdk/compare/49a82d880636a632f4a3471b14b1b1b29ce1d5e6...master

Your commit was automatically rebased without conflicts.

[openjdk[bot]]

@coleenp Pushed as commit 4edf791aecd432ecde00652acfaabddf136f4ca7.

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