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Chris Tate
7b83558f52
Atomics operations on 8-, 16- and 32-bit integer arrays are sequentially consistent atomic instructions on the element, and no longer take the process-wide shared-memory lock. Other reads and writes of shared storage are relaxed atomic accesses: element reads and writes access the element, and copies, fills, conversions, searches and sorts read shared bytes into a private copy and write back only the range they change, so concurrent accesses to the same bytes are free of data races. Non-shared storage keeps its plain memory accesses. Atomics.wait and Atomics.notify queue waiters in buckets chosen by location, each with its own lock and condition variable, so waiting threads no longer serialize other Atomics. Atomics.store answers +0 for a value that truncates to -0, as Node does. The shared storage runtime test also runs under ThreadSanitizer.
8 lines
2.5 KiB
Plaintext
8 lines
2.5 KiB
Plaintext
`node:worker_threads` runs workers as native threads. Worker entry points must resolve at build time: use a source-relative `new URL("./worker.ts", import.meta.url)`, the current module URL, an absolute path, or CommonJS `__filename`. Each worker initializes its own module state, event loop, environment snapshot, and reference-counted heap. Nested workers inherit their parent's environment snapshot. Supported constructor options are `workerData` and `argv`; runtime paths, `eval`, loaders, custom stdio, shared environments, resource limits, and transfer lists are unsupported. Worker argument strings containing null bytes are also unsupported.
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Workers support `online`, `message`, `error`, and `exit` events, `postMessage`, `terminate`, `ref`, and `unref`. The parent port supports message listeners, `postMessage`, `close`, `start`, `ref`, `unref`, and `hasRef`. Messages clone primitives, plain object graphs, arrays, errors, ArrayBuffers, typed arrays, and DataViews, preserving cycles and aliases. Program class instances arrive as plain objects with their own data properties, without their prototype, methods, accessors, or private fields, as in Node. Functions, proxies, other native handles, and nonempty transfer lists are refused. SharedArrayBuffers share their backing storage while retaining separate wrappers in each thread. Graphs made immutable with `@scriptc/threads` are passed by reference instead of cloned; see [Sharing Data Between Workers](/docs/threads).
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SharedArrayBuffer storage is fixed-length. Atomics supports integer `load`, `store`, `exchange`, `compareExchange`, `add`, `sub`, `and`, `or`, and `xor` over 8-, 16-, and 32-bit integer arrays. `wait` and `notify` use Int32Array views; BigInt atomics, `waitAsync`, and growable buffers are unsupported. Atomics operations run as sequentially consistent atomic instructions and take no lock. Other reads and writes of shared storage access each element atomically; a copy, fill, or conversion that runs while another thread writes the same storage can observe some of those writes, as in Node. `terminate` unwinds at runtime checkpoints, including loops and parked atomic waits, without running JavaScript catch or finally blocks. Blocking native calls finish before the next checkpoint.
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Workers are unsupported in WASI, compiled libraries, and executables that use foreign-thread native callbacks. Ordinary callbacks that run on their owning script thread remain supported. Shared byte storage cannot expose unmanaged FFI pointers; copy it into an ordinary Buffer before passing it to native code.
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