swift-threads

Thread-layer compositions for Swift. Houses composed types that build on Kernel.Thread primitives but are neither raw syscall wrappers (that's swift-kernel) nor Swift Executor protocol conformances (that's swift-executors). Layer 3 (Foundations) of the Swift Institute five-layer architecture.

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Package mission

• swift-kernel (L3): thin syscall-adjacent wrappers over L1 primitives
• swift-executors (L3): types that ARE Swift Executors (SerialExecutor, TaskExecutor)
• swift-threads (L3, this package): thread-layer compositions — admission, coordination, worker patterns

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Products (today)

Product	Contents
Thread Pool	Kernel.Thread.Pool — admission-gated closure dispatch over Kernel.Thread.Executor.Sharded

Product	Contents
Thread Barrier	Kernel.Thread.Barrier (rendezvous coordination over Synchronizer.Blocking<1>)
Thread Gate	Kernel.Thread.Gate (one-shot rendezvous over Synchronizer.Blocking<1>)
Thread Semaphore	Kernel.Thread.Semaphore (thread-blocking counting semaphore over Synchronizer.Blocking<2>; distinct from Async.Semaphore)
Thread Worker	Kernel.Thread.Worker + Token
Thread Actor	Kernel.Thread.Actor (executor-backed actor)
Threads	umbrella re-exporting all of the above

The underlying synchronization substrate (Synchronizer.Blocking<N> — mutex + N condvars) lives in the sibling swift-synchronizers L3 package. swift-threads consumes it directly via the Synchronizer Blocking product.

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Installation

Package.swift

.package(path: "../swift-threads")

Target dependency

.target(
    name: "YourTarget",
    dependencies: [
        .product(name: "Thread Pool", package: "swift-threads")
    ]
)

Consumers should prefer narrow product imports — Thread Pool, Thread Semaphore, etc. — over the umbrella Threads unless they genuinely need the full stack.

Requirements

• Swift 6.3+
• macOS 26.0+ / iOS 26.0+ / tvOS 26.0+ / watchOS 26.0+
• Linux (Ubuntu 22.04+)
• Windows (Swift 6.3+)

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Quick Start — Thread Pool

import Thread_Pool

let pool = Kernel.Thread.Pool()
defer { pool.shutdown() }

let result = try await pool.run { blockingSyscall() }

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Architecture

swift-threads       ← thread-layer compositions (this package)
     |
swift-executors     ← Swift Executor conformances
     |
swift-kernel        ← syscall-adjacent wrappers
     |
swift-kernel-primitives  ← raw syscall atoms

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License

Apache 2.0 — See LICENSE for details.