ci: replace global RUST_TEST_THREADS=1 with per-crate --test-threads=1#280
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Brooooooklyn merged 5 commits intomainfrom Mar 21, 2026
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ci: replace global RUST_TEST_THREADS=1 with per-crate --test-threads=1#280Brooooooklyn merged 5 commits intomainfrom
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On musl, fork() is unsafe when other threads exist — even threads sleeping on a futex leave musl internal state that the child inherits in an inconsistent form, causing SIGSEGV between fork and exec. A process-wide mutex (PTY_LOCK) cannot fix this because the test harness still spawns multiple threads (one per test). The real fix is --test-threads=1 for PTY test binaries, which ensures only one thread exists during fork. Split `cargo test` into: - Non-PTY tests: run in parallel (default thread count) - PTY tests (pty_terminal, pty_terminal_test, vite_task_bin): run with --test-threads=1 This removes the global RUST_TEST_THREADS=1 that forced ALL tests to run sequentially, improving CI speed for non-PTY tests. https://claude.ai/code/session_011H8UR3gS6hoyQAf2x7Dfw8
On musl libc, fork() in a multi-threaded process is unsafe because musl internal state (locks, allocator metadata) in other threads can be left inconsistent in the child, causing SIGSEGV/SIGBUS. portable_pty uses pre_exec() for PTY setup, which forces Rust's Command to use fork()+exec() instead of posix_spawn(). This commit bypasses portable_pty's spawn_command() on musl and uses posix_spawn() directly, which musl implements via clone(CLONE_VM|CLONE_VFORK) — avoiding fork() entirely. PTY setup is handled via spawn attributes and file actions: - POSIX_SPAWN_SETSID for session leadership (replaces setsid()) - addopen() on the slave TTY path sets the controlling terminal - SETSIGDEF/SETSIGMASK for signal cleanup (replaces manual signal reset) This allows all tests (including PTY tests) to run in parallel on musl, removing the need for per-crate --test-threads=1. https://claude.ai/code/session_011H8UR3gS6hoyQAf2x7Dfw8
…lel tests" This reverts commit 4dd37ba.
On musl libc, fork() in a multi-threaded process is unsafe because musl internal state (locks, allocator metadata) in other threads can be left inconsistent in the child, causing SIGSEGV/SIGBUS. cargo-nextest runs each test in its own process (not thread), so fork() happens from a mostly single-threaded context. Tests still execute in parallel across processes, maintaining fast CI times without SIGSEGV. This replaces the per-crate --test-threads=1 workaround which serialized all tests within each crate. https://claude.ai/code/session_011H8UR3gS6hoyQAf2x7Dfw8
…o test cargo-nextest can't discover tests in packages with `harness = false` (e2e_snapshots, plan_snapshots) because they output custom formats instead of the standard libtest listing. Split the musl test run: - nextest for standard-harness tests (parallel, per-process isolation) - cargo test for custom-harness packages (already run sequentially) https://claude.ai/code/session_011H8UR3gS6hoyQAf2x7Dfw8
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Summary
RUST_TEST_THREADS=1from the musl CI jobcargo testinto non-PTY tests (parallel) and PTY tests (--test-threads=1)Details
On musl,
fork()is unsafe when other threads exist — even threads sleeping on a futex leave musl internal state that the child inherits in an inconsistent form, causing SIGSEGV between fork and exec.A process-wide mutex (
PTY_LOCK) cannot fix this because the test harness still spawns multiple threads. The real fix is--test-threads=1for PTY test binaries only (pty_terminal,pty_terminal_test,vite_task_bin), ensuring a single thread exists during fork.Test plan
https://claude.ai/code/session_011H8UR3gS6hoyQAf2x7Dfw8