Refactor how concurrency support is enabled in a Store
#12416
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This commit is an extension/refactor of bytecodealliance#12377 and bytecodealliance#12379. Notably this decouples the runtime behavior of Wasmtime from enabled/disabled WebAssembly proposals. This enables the `wasmtime serve` subcommand, for example, to continue to disallow component-model-async by default but continue to use `*_concurrent` under the hood. Specifically a new `Config::concurrency_support` knob is added. This is plumbed directly through to `Tunables` and takes over the preexisting `component_model_concurrency` field. This field configures whether tasks/etc are enabled at runtime for component-y things. The default value of this configuration option is the same as `cfg!(feature = "component-model-async")`, and this field is required if component-model-async wasm proposals are enabled. It's intended that eventually this'll affect on-by-default wasm features in Wasmtime depending if the support is compiled in. This results in a subtle shift in behavior where component-model-async concurrency is used by default now because the feature is turned on by default, even though the wasm features are off-by-default. This required adjusting a few indices expected in runtime tests due to tasks/threads being allocated in index spaces. Finally, this additionally denies access at runtime to `Linker::*_concurrent` when concurrent support is disabled as otherwise the various runtime data structures won't be initialized and panics will happen. Closes bytecodealliance#12393
alexcrichton
requested review from
cfallin and
fitzgen
and removed request for
a team
Used to update disas tests to show that, when disabled, old codegen quality is preserved
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cc @dicej too |
dicej
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Jan 23, 2026
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This commit is an extension/refactor of #12377 and #12379. Notably this
decouples the runtime behavior of Wasmtime from enabled/disabled
WebAssembly proposals. This enables the
wasmtime servesubcommand, forexample, to continue to disallow component-model-async by default but
continue to use
*_concurrentunder the hood.Specifically a new
Config::concurrency_supportknob is added. This isplumbed directly through to
Tunablesand takes over the preexistingcomponent_model_concurrencyfield. This field configures whethertasks/etc are enabled at runtime for component-y things. The default
value of this configuration option is the same as
cfg!(feature = "component-model-async"), and this field is required ifcomponent-model-async wasm proposals are enabled. It's intended that
eventually this'll affect on-by-default wasm features in Wasmtime
depending if the support is compiled in.
This results in a subtle shift in behavior where component-model-async
concurrency is used by default now because the feature is turned on by
default, even though the wasm features are off-by-default. This required
adjusting a few indices expected in runtime tests due to tasks/threads
being allocated in index spaces.
Finally, this additionally denies access at runtime to
Linker::*_concurrentwhen concurrent support is disabled as otherwisethe various runtime data structures won't be initialized and panics will
happen.
Closes #12393