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* Synchronize both versions of actor_counters.swift test

* Synchronize on Job address

Make sure to synchronize on Job address (AsyncTasks are Jobs, but not
all Jobs are AsyncTasks).

* Add fprintf debug output for TSan acquire/release

* Add tsan_release edge on task creation

without this, we are getting false data races between when a task
is created and immediately scheduled on a different thread.

False positive for `Sanitizers/tsan/actor_counters.swift` test:
```
WARNING: ThreadSanitizer: data race (pid=81452)
  Read of size 8 at 0x7b2000000560 by thread T5:
    #0 Counter.next() <null>:2 (a.out:x86_64+0x1000047f8)
    #1 (1) suspend resume partial function for worker(identity:counters:numIterations:) <null>:2 (a.out:x86_64+0x100005961)
    #2 swift::runJobInEstablishedExecutorContext(swift::Job*) <null>:2 (libswift_Concurrency.dylib:x86_64+0x280ef)

  Previous write of size 8 at 0x7b2000000560 by main thread:
    #0 Counter.init(maxCount:) <null>:2 (a.out:x86_64+0x1000046af)
    #1 Counter.__allocating_init(maxCount:) <null>:2 (a.out:x86_64+0x100004619)
    #2 runTest(numCounters:numWorkers:numIterations:) <null>:2 (a.out:x86_64+0x100006d2e)
    #3 swift::runJobInEstablishedExecutorContext(swift::Job*) <null>:2 (libswift_Concurrency.dylib:x86_64+0x280ef)
    #4 main <null>:2 (a.out:x86_64+0x10000a175)
```

New edge with this change:
```
[4357150208] allocate task 0x7b3800000000, parent = 0x0
[4357150208] creating task 0x7b3800000000 with parent 0x0
[4357150208] tsan_release on 0x7b3800000000    <<< new release edge
[139088221442048] tsan_acquire on 0x7b3800000000
[139088221442048] trying to switch from executor 0x0 to 0x7ff85e2d9a00
[139088221442048] switch failed, task 0x7b3800000000 enqueued on executor 0x7ff85e2d9a00
[139088221442048] enqueue job 0x7b3800000000 on executor 0x7ff85e2d9a00
[139088221442048] tsan_release on 0x7b3800000000
[139088221442048] tsan_release on 0x7b3800000000
[4357150208] tsan_acquire on 0x7b3800000000
counters: 1, workers: 1, iterations: 1
[4357150208] allocate task 0x7b3c00000000, parent = 0x0
[4357150208] creating task 0x7b3c00000000 with parent 0x0
[4357150208] tsan_release on 0x7b3c00000000    <<< new release edge
[139088221442048] tsan_acquire on 0x7b3c00000000
[4357150208] task 0x7b3800000000 waiting on task 0x7b3c00000000, going to sleep
[4357150208] tsan_release on 0x7b3800000000
[4357150208] tsan_release on 0x7b3800000000
[139088221442048] getting current executor 0x0
[139088221442048] tsan_release on 0x7b3c00000000
...
```

rdar://78932849

* Add static_cast<Job *>()

* Move TSan release edge to swift_task_enqueueGlobal()

Move the TSan release edge from `swift_task_create_commonImpl()` to
`swift_task_enqueueGlobalImpl()`.  Task creation itself is not an event
that needs synchronization, but rather that task creation "happens
before" execution of that task on another thread.

This edge is usually added when the task is scheduled via
`swift_task_enqueue()` (which then usually calls
`swift_task_enqueueGlobal()`).  However, not all task scheduling goes
through the `swift_task_enqueue()` funnel as some places call the more
specific `swift_task_enqueueGlobal()` directly.  So let's annotate this
function (duplicate edges aren't harmful) to ensure we cover all
schedule events, including newly-created tasks (our original problem
here).

rdar://78932849

Co-authored-by: Julian Lettner <julian.lettner@apple.com>
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Welcome to Swift

Swift is a high-performance system programming language. It has a clean and modern syntax, offers seamless access to existing C and Objective-C code and frameworks, and is memory safe by default.

Although inspired by Objective-C and many other languages, Swift is not itself a C-derived language. As a complete and independent language, Swift packages core features like flow control, data structures, and functions, with high-level constructs like objects, protocols, closures, and generics. Swift embraces modules, eliminating the need for headers and the code duplication they entail.

To learn more about the programming language, visit swift.org.

Contributing to Swift

Contributions to Swift are welcomed and encouraged! Please see the Contributing to Swift guide.

To be a truly great community, Swift.org needs to welcome developers from all walks of life, with different backgrounds, and with a wide range of experience. A diverse and friendly community will have more great ideas, more unique perspectives, and produce more great code. We will work diligently to make the Swift community welcoming to everyone.

To give clarity of what is expected of our members, Swift has adopted the code of conduct defined by the Contributor Covenant. This document is used across many open source communities, and we think it articulates our values well. For more, see the Code of Conduct.

Getting Started

If you are interested in:

We also have an FAQ that answers common questions.

Swift Toolchains

Building

Swift toolchains are created using the script build-toolchain. This script is used by swift.org's CI to produce snapshots and can allow for one to locally reproduce such builds for development or distribution purposes. A typical invocation looks like the following:

  $ ./swift/utils/build-toolchain $BUNDLE_PREFIX

where $BUNDLE_PREFIX is a string that will be prepended to the build date to give the bundle identifier of the toolchain's Info.plist. For instance, if $BUNDLE_PREFIX was com.example, the toolchain produced will have the bundle identifier com.example.YYYYMMDD. It will be created in the directory you run the script with a filename of the form: swift-LOCAL-YYYY-MM-DD-a-osx.tar.gz.

Beyond building the toolchain, build-toolchain also supports the following (non-exhaustive) set of useful options::

  • --dry-run: Perform a dry run build. This is off by default.
  • --test: Test the toolchain after it has been compiled. This is off by default.
  • --distcc: Use distcc to speed up the build by distributing the c++ part of the swift build. This is off by default.
  • --sccache: Use sccache to speed up subsequent builds of the compiler by caching more c++ build artifacts. This is off by default.

More options may be added over time. Please pass --help to build-toolchain to see the full set of options.

Installing into Xcode

On macOS if one wants to install such a toolchain into Xcode:

  1. Untar and copy the toolchain to one of /Library/Developer/Toolchains/ or ~/Library/Developer/Toolchains/. E.x.:
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  $ tar -xzf swift-LOCAL-YYYY-MM-DD-a-osx.tar.gz -C ~/

The script also generates an archive containing debug symbols which can be installed over the main archive allowing symbolication of any compiler crashes.

  $ sudo tar -xzf swift-LOCAL-YYYY-MM-DD-a-osx-symbols.tar.gz -C /
  $ tar -xzf swift-LOCAL-YYYY-MM-DD-a-osx-symbols.tar.gz -C ~/
  1. Specify the local toolchain for Xcode's use via Xcode->Toolchains.

Build Failures

Try the suggestions in Troubleshooting build issues.

Make sure you are using the correct release of Xcode.

If you have changed Xcode versions but still encounter errors that appear to be related to the Xcode version, try passing --clean to build-script.

When a new version of Xcode is released, you can update your build without recompiling the entire project by passing --reconfigure to build-script.

Learning More

Be sure to look at the documentation index for a bird's eye view of the available documentation. In particular, the documents titled Debugging the Swift Compiler and Continuous Integration for Swift are very helpful to understand before submitting your first PR.