Stream: git-wasmtime

Topic: wasmtime / PR #6833 Use a worker thread for stdin on Unix...

Wasmtime GitHub notifications bot (Aug 10 2023 at 19:00):

alexcrichton requested jameysharp for a review on PR #6833.

Wasmtime GitHub notifications bot (Aug 10 2023 at 19:02):

alexcrichton requested wasmtime-core-reviewers for a review on PR #6833.

Wasmtime GitHub notifications bot (Aug 10 2023 at 19:04):

alexcrichton opened PR #6833 from alexcrichton:use-worker-thread-unix to bytecodealliance:main:

Currently stdin on Unix uses AsyncFd after setting the nonblocking flag on the stdin file descriptor. This cannot generally be relied on to succeed or work well in cases such as:

• On Linux if stdin is a file (e.g. wasmtime < ./foo.txt) then that can't be added to epoll and epoll_ctl fails with EPERM.

• On macOS if stdin is /dev/null that can't be added to kqueue and fails with EINVAL.

Currently this causes Wasmtime to panic due to a .unwrap() in failing to register stdin. To fix this this commit removes the Unix-specific logic using AsyncFd and instead falls back to unconditionally using a spawned thread like Windows does. This does mean it's a little less lightweight but should be more robust in situations like the above.

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Wasmtime GitHub notifications bot (Aug 10 2023 at 19:07):

alexcrichton requested pchickey for a review on PR #6833.

Wasmtime GitHub notifications bot (Aug 11 2023 at 00:33):

alexcrichton updated PR #6833.

Wasmtime GitHub notifications bot (Aug 11 2023 at 00:33):

alexcrichton edited PR #6833:

Not all file descriptors can get registered with epoll, for example
files on Linux or /dev/null on macOS return errors. In these
situations the fallback of the worker thread implementation is used
instead.

Last updated: Dec 13 2025 at 19:03 UTC