Make GlobalContext Sync #15967
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Make GlobalContext Sync #15967
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This will make it easier to change the implementation in the future.
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… 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`
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What does this PR try to resolve?
By making
GlobalContextSync, 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
GlobalContextand structs used in its fieldsRefCell-s were replaced by either anstd::sync::Mutexor anstd::sync::RwLock, depending on API needsLazyCell-s were replaced by a newOnceLockimplementation backed bystd::sync::OnceLock, emulating unstable features needed by cargoLazyCell/OnceLockfrom fields where the initialization function is just aMutex<HashMap>::default()util::context::tests::sync_contexttest that does not compile ifGlobalContextis notSyncHow to test and review this PR?
This PR should add no user-facing changes. Tests must pass and benchmarks must report no changes.