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60 lines
2.2 KiB
Markdown
60 lines
2.2 KiB
Markdown
# Pthread implementations
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WAMR has two pthread implementations available as of writing this.
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These implementations are not ABI-compatible. You at least need to rebuild
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your wasm modules when migrating from one pthread implementation to another.
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For new users, we recommend to use (or at least experiment)
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the new wasi-threads based implementation.
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In future, we might remove the old implementation.
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## WAMR lib-pthread (old)
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* The pthread API is directly implemented as host functions in WAMR.
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(`WAMR_BUILD_LIB_PTHREAD`)
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* Only minimum API is implemented as of writing this.
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(eg. no pthread barriers)
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* WAMR-specific ABI
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* [Known limitations](pthread_library.md#known-limits)
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## wasi-threads (new)
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* The pthread API is implemented in wasi-libc, based on
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[wasi-threads](https://github.com/WebAssembly/wasi-threads)
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and [WASM threads](https://github.com/WebAssembly/threads) proposals.
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* It requires a recent-enough version of wasi-libc. The experimental support
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is included in
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[wasi-sdk 20.0](https://github.com/WebAssembly/wasi-sdk/releases/tag/wasi-sdk-20)
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or later.
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To build your application, cmake users can use the
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[cmake toolchain file](https://github.com/WebAssembly/wasi-sdk/blob/main/wasi-sdk-pthread.cmake)
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provided by wasi-sdk.
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* wasi-threads is implemented as a host function in WAMR.
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(`WAMR_BUILD_LIB_WASI_THREADS`)
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* The ABI is specified in wasi-threads proposal.
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You can run the same wasm modules on other runtimes which implement
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the proposal. (wasmtime, toywasm, ...)
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* Basically more feature-rich and complete than WAMR lib-pthread.
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**EXCEPTION**: `pthread_exit` is not available as of writing this.
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If `pthread_exit` is important for your use cases, please speak up in
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the [GitHub issue](https://github.com/WebAssembly/wasi-threads/issues/7).
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**EXCEPTION**: For threads created by `pthread_create`, the AUX stack
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(aka C shadow stack) overflow detection mechanism is disabled as of
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writing this.
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If it's important for your use cases, please speak up in the
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[GitHub issue](https://github.com/WebAssembly/wasi-threads/issues/12).
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# References
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* https://github.com/bytecodealliance/wasm-micro-runtime/issues/1790
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