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Welcome to the

TSAN Project!

The goal of this Project is to explore and incubate a Thread SANitizing SANitizer (TSAN) feature that could be integrated into the HotSpot JVM and the JVM Tool Interface (JVM TI).  This includes working, evaluating, and incubating a Thread Sanitizer implementation for Java.

The rest of this page will provide basic information for downloading, building, and testing Java TSAN.

Note: Java TSAN is not working yet and will not be able to provide any data race information yet. The information below is really how to clone/test for developers and testers:

Cloning:

hg clone --branch tsan http://hg.openjdk.java.net/tsan/dev jdk-tsan

Installing:

TODO: since TSAN is not even integrated yet, the JDK you just branched is the mainline.

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Prerequisites

Java TSAN has only been tested on 64-bit Linux. It may work on other platforms that LLVM TSAN supports with some build changes.

Java TSAN is dependent on the C/C++ ThreadSanitizer implementation for GCC/LLVM. Java TSAN requires a new API for proper symbolization of Java stack traces, which is only available in update-to-date versions of C/C++ ThreadSanitizer. This requires building OpenJDK with LLVM 7.0 or later, or GCC 9 or later. Currently we recommend developers and testers use LLVM 8.0.

Building

Java TSAN implementation is in the "tsan" branch in the Git repository. Developers need to clone this branch:

git clone --branch tsan https://github.com/openjdk/tsan.git jdk-tsan

Newer toolchains come with new warnings and the codebase hasn't been cleaned up for those warnings yet, so --disable-warnings-as-errors is needed.

Java TSAN exists as a JVM feature "tsan", which is enabled by default on the "tsan" branch in the repository. It can be disabled with the configure flag "--with-jvm-features=-tsan".

To build OpenJDK with LLVM, pass the configure flags "--with-toolchain-type=clang --with-toolchain-path=<path_to_llvm_root_dir>/bin".

Running

Note: the method of including the TSAN runtime in the JVM is not finalized and will definitely could change in the future.

First ensure you have libtsan.so available. e.g.:

sudo apt install libgcc-8-dev

ls -l /usr/lib/gcc/x86_64-linux-gnu/8/libtsan.so

Run Java with TSAN enabled:

LD_PRELOAD=/usr/lib/gcc/x86_64-linux-gnu/8/libtsan.so ./images/jdk/bin/java -XX:+ThreadSanitizer

Testing:Currently

, the The tests for TSAN are here:at test/hotspot/jtreg/tsan/

make run-test  test TEST="jtreg:test/hotspot/jtreg/tsan"

The tests are currently passing if TSAN is not enabled; once TSAN starts coming online, the tests will flip their assertions/expectations.

Resources

Known Issues

• We have only tested TSAN with the G1 garbage collector. TSAN may not work correctly with other garbage collectors.
• For a moderately scaled application, TSAN will likely report data races from OpenJDK's own libraries. Many of these races are benign, but these race reports hurt TSAN's usability. You could specific a file via -XX:ThreadSanitizerIgnoreFile to suppress such races (refer to this doc for its format). We plan to publish a list of commonly suppressed races in the future.

Resources

• TSAN Project
• TSAN JEP proposalTsan Project
• Repositories
• Mailing list: tsan-dev