Make GlobalContext Sync #15967

susitsm · 2025-09-15T08:02:43Z

What does this PR try to resolve?

By making GlobalContext Sync, it will become much easier to parallelize parts of cargo. A concrete example is #15676.

It was my understanding from #15934 (comment) that this would be a welcome change by the cargo team.

Overview

In GlobalContext and structs used in its fields

RefCell-s were replaced by either an std::sync::Mutex or an std::sync::RwLock, depending on API needs
LazyCell-s were replaced by a new OnceLock implementation backed by std::sync::OnceLock, emulating unstable features needed by cargo
Removed LazyCell/OnceLock from fields where the initialization function is just a Mutex<HashMap>::default()
added util::context::tests::sync_context test that does not compile if GlobalContext is not Sync

How to test and review this PR?

This PR should add no user-facing changes. Tests must pass and benchmarks must report no changes.

rustbot · 2025-09-15T08:02:48Z

r? @weihanglo

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src/cargo/util/context/once_lock.rs

src/cargo/util/context/mod.rs

src/cargo/util/cache_lock.rs

src/cargo/util/context/mod.rs

epage · 2025-09-16T15:48:02Z

Thanks!

epage · 2025-09-16T17:55:34Z

FYI we are fine with editing existing history and, in a case like this, I would prefer it over having fixup commits later in the history as it makes the commits I'm reviewing more understandable on their own.

src/cargo/core/registry.rs

This will make it easier to change the implementation in the future.

… is just a HashMap::defualt()

Previously, `gctx.shell().verbosity()` was used to check that `gctx.shell` is not borrowed. Since shell is now behind a `Mutex` and not a `RefCell`, this would hang waiting for the unlock instead panicking. Borrow state checking is now done using `Mutex::try_lock` in `GlobalContext::debug_assert_shell_not_borrowed`

epage · 2025-09-22T15:45:59Z

Thanks!

Update cargo submodule 17 commits in 966f94733bbc94ca51ff9f1e4c49ad250ebbdc50..f2932725b045d361ff5f18ba02b1409dd1f44e71 2025-09-16 17:24:45 +0000 to 2025-09-24 11:31:26 +0000 - fix: use `host-tuple` for host target subsitution (rust-lang/cargo#16003) - test(build-std): move away from panic_immediate_abort (rust-lang/cargo#16006) - fix: Sparse URLs in `TomlLockfileSourceId` (rust-lang/cargo#15990) - refactor(gctx): extract toml dotted keys validation (rust-lang/cargo#15998) - feat: Add lint for global use of `hint-mostly-unused` (rust-lang/cargo#15995) - Make GlobalContext Sync (rust-lang/cargo#15967) - chore(deps): update cargo-semver-checks to v0.44.0 (rust-lang/cargo#15993) - fix(frontatter): Only allow horizontal whitespace after fences (rust-lang/cargo#15975) - docs: Add Lockfile schemas docs (rust-lang/cargo#15989) - Add parallel frontend to the build performance guide (rust-lang/cargo#15970) - chore(deps): update msrv (3 versions) to v1.88 (rust-lang/cargo#15988) - chore(deps): update msrv (1 version) to v1.90 (rust-lang/cargo#15984) - feat(cargo-util-schemas): Move lockfile schemas (rust-lang/cargo#15980) - Clarify multiple version requirement behavior (rust-lang/cargo#15979) - Adds ghostty as supported terminal for term integration (OSC 9;4) (rust-lang/cargo#15977) - docs(team): Fixed broken office hours link (rust-lang/cargo#15976) - docs: Clarify git sources vs git registries in source replacement documentation (rust-lang/cargo#15974) r? ghost

rustbot assigned weihanglo Sep 15, 2025