Wasmtime GitHub notifications bot (Nov 17 2025 at 19:27): Wasmtime GitHub notifications bot (Nov 17 2025 at 19:27):alexcrichton opened PR #12036 from alexcrichton:downgrade-threads to bytecodealliance:main:
This commit is borne out of a fuzz bug that was opened recently. The fuzz bug specifically has to do with fallout from #12022, specifically
SharedMemorybeing used to allocated instead ofMemory. In this situation the resource limiter is no longer consulted meaning that shared memories bypass this and aren't caught by OOM checks. This is currently by design becauseSharedMemoryinstances don't know which resource limiter to hook into per-store.More generally though the implementation of wasm threads, while workable in Wasmtime, has a number of known relatively large deficiencies. These were not resolved prior to ungating the wasm proposal (that's on me) but nevertheless the quality of implementation is not quite up to "tier 1 par" with the rest of what Wasmtime offers. Given that I'm proposing that threads is downgraded to tier 2 for now which means, primarily, that we won't issue CVEs for issues with it. The proposal is still on-by-default and usable-by-default, but my hope is to reflect the current level of quality in Wasmtime with this adjustment.
This commit shuffles around some documentation of wasm proposals to split it into tier 1/2/3 instead of on/off-by-default and then adds a column for whether the proposal is on-by-default.
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Wasmtime GitHub notifications bot (Nov 17 2025 at 19:27):alexcrichton requested wasmtime-fuzz-reviewers for a review on PR #12036.
Wasmtime GitHub notifications bot (Nov 17 2025 at 19:27):alexcrichton requested cfallin for a review on PR #12036.
Wasmtime GitHub notifications bot (Nov 17 2025 at 19:27):alexcrichton requested wasmtime-default-reviewers for a review on PR #12036.
Wasmtime GitHub notifications bot (Nov 17 2025 at 19:43):cfallin submitted PR review:
No objections from me at least; not sure if we want to discuss in the Wasmtime meeting or if anyone else has any input on the decision...
Wasmtime GitHub notifications bot (Nov 17 2025 at 19:53):alexcrichton commented on PR #12036:
Good point yeah, let's discuss in a meeting
Wasmtime GitHub notifications bot (Nov 17 2025 at 22:45):github-actions[bot] commented on PR #12036:
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Wasmtime GitHub notifications bot (Nov 21 2025 at 02:23):alexcrichton requested dicej for a review on PR #12036.
Wasmtime GitHub notifications bot (Nov 21 2025 at 02:23):alexcrichton requested wasmtime-core-reviewers for a review on PR #12036.
Wasmtime GitHub notifications bot (Nov 21 2025 at 02:23):alexcrichton updated PR #12036.
Wasmtime GitHub notifications bot (Nov 21 2025 at 02:25):alexcrichton commented on PR #12036:
Ok updated this from today's discussion in the Wasmtime meeting namely:
- The threads proposal is still downgraded to tier 2
- The WebAssembly
threadsfeature continues to be enabled by default- Creation of shared memories is now disabled by default
Notably there's not actually any means of exercising the threading/problematic parts of the API, namely
SharedMemory. That being said single-threaded atomics are still allowed in wasm which should work just fine.
Wasmtime GitHub notifications bot (Nov 21 2025 at 02:25):alexcrichton updated PR #12036.
Wasmtime GitHub notifications bot (Nov 21 2025 at 04:47):github-actions[bot] commented on PR #12036:
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Wasmtime GitHub notifications bot (Nov 21 2025 at 14:37):alexcrichton updated PR #12036.
Wasmtime GitHub notifications bot (Nov 21 2025 at 14:56):alexcrichton updated PR #12036.
Wasmtime GitHub notifications bot (Nov 21 2025 at 15:23):alexcrichton updated PR #12036.
Wasmtime GitHub notifications bot (Nov 21 2025 at 15:34):alexcrichton updated PR #12036.
Wasmtime GitHub notifications bot (Nov 21 2025 at 15:54):alexcrichton updated PR #12036.
Wasmtime GitHub notifications bot (Nov 24 2025 at 14:52):dicej submitted PR review.
Wasmtime GitHub notifications bot (Nov 24 2025 at 16:20):alexcrichton updated PR #12036.
Wasmtime GitHub notifications bot (Nov 24 2025 at 16:20):alexcrichton has enabled auto merge for PR #12036.
Wasmtime GitHub notifications bot (Nov 24 2025 at 17:35):alexcrichton merged PR #12036.
Last updated: Dec 06 2025 at 07:03 UTC