use __asyncify in fd_read, allowing signal processing and DL operatio…

[Arshia001]

…ns to happen while waiting for data

This change should resolve both #6472 and #6426.

Description

[Copilot]

Pull request overview

Updates WASIX fd_read to use the signal/DL-operation-aware asyncify path so that blocking reads can be interrupted (EINTR) and dynamic linking work can continue while waiting for input, addressing reported hangs and missed signal handling.

Changes:

• Switches fd_read’s file/socket/pipe read paths from __asyncify_light to __asyncify.
• Adds an iovec extraction helper to release the MemoryView borrow prior to asyncify.
• Pumps pending dynamic-link operations while __asyncify work is pending (in SignalPoller).

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 6 comments.

File	Description
lib/wasix/src/syscalls/wasi/fd_read.rs	Refactors fd_read to run under __asyncify and restructures iovec handling to avoid holding a MemoryView borrow across asyncify.
lib/wasix/src/syscalls/mod.rs	Ensures pending dynamic-link operations are processed while __asyncify is polling pending work.

[Copilot]

Pull request overview

This PR updates WASIX fd_read to use the signal/DL-operation aware asyncify path while blocked, aiming to prevent deadlocks during dynamic library operations and allow signal processing to interrupt blocking reads (resolving #6472 and #6426).

Changes:

• Switch fd_read blocking paths (file/socket/pipe) to use __asyncify and refactor iovec handling to avoid holding the MemoryView borrow across asyncify.
• Improve __asyncify polling to also drive pending link operations and avoid returning EINTR for wakeup-only signals.
• Add a regression test module (stdin-dlopen-race) plus a Rust harness helper to run wasm with a custom stdin that never EOFs.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
lib/wasix/src/syscalls/wasi/fd_read.rs	Refactors fd_read to use __asyncify and introduces raw-pointer iovec extraction to enable exclusive ctx during asyncify.
lib/wasix/src/syscalls/mod.rs	Ensures asyncify polling drives pending link operations and refines signal handling to avoid spurious EINTR on wakeups.
lib/wasix/tests/wasm_tests/mod.rs	Adds run_wasm_with_stdin helper for tests that need a non-EOF stdin source.
lib/wasix/tests/wasm_tests/fd_tests.rs	Adds a regression test ensuring a blocking stdin read doesn’t deadlock dlopen.
lib/wasix/tests/wasm_tests/fd_tests/stdin-dlopen-race/main.c	New wasm guest program reproducing the stdin-read vs dlopen deadlock scenario.
lib/wasix/tests/wasm_tests/fd_tests/stdin-dlopen-race/side.c	Minimal shared library for the dlopen regression test.
lib/wasix/tests/wasm_tests/fd_tests/stdin-dlopen-race/build.sh	Build script for compiling the new regression test artifacts.

[syrusakbary]

I'm a bit concerned on this one, doing a asyncify into each read might introduce a lot of slowdown. Do you think that will be the case @Arshia001 ?