Add data_ptr method to Mutex and RwLock
Implementation of https://github.com/rust-lang/rust/issues/140368 / https://github.com/rust-lang/libs-team/issues/531.
I tried to write a useful safety section about when it is safe to read or write through the returned pointers, but couldn't come up with something nice. Hoping this PR is still useful without that. I'm happy to add any doc strings other people come up with if needed before merge, of course.
Unresolved questions:
- Return a `LockResult` or not?
- Return `*mut T` like existing APIs (`Cell::as_ptr` / `MaybeUninit::as[_mut]_ptr` / `Vec::as_ptr` / ...) or be more precise and return `NonNull<T>`?
Implement (part of) ACP 429: add `DerefMut` to `Lazy[Cell/Lock]`
`DerefMut` is instantly stable, as a trait impl. That means this needs an FCP.
``@rustbot`` label +needs-fcp
https://github.com/rust-lang/libs-team/issues/429
sync::mpsc: prevent double free on `Drop`
This PR is fixing a regression introduced by #121646 that can lead to a double free when dropping the channel.
The details of the bug can be found in the corresponding crossbeam PR https://github.com/crossbeam-rs/crossbeam/pull/1187
This PR is fixing a regression introduced by #121646 that can lead to a
double free when dropping the channel.
The details of the bug can be found in the corresponding crossbeam PR
https://github.com/crossbeam-rs/crossbeam/pull/1187
Signed-off-by: Petros Angelatos <petrosagg@gmail.com>
Move some std tests to integration tests
Unit tests directly inside of standard library crates require a very fragile way of building that is hard to reproduce outside of bootstrap.
Follow up to https://github.com/rust-lang/rust/pull/133859
docs: Documented Send and Sync requirements for Mutex + MutexGuard
This an attempt to continue where #123225 left off.
I did some light clean up from the work done in that PR.
I also documented the `!Send` + `Sync` implementations for `MutexGuard` to the best of my knowledge.
Let me know if I got anything wrong 😄fixes#122856
cc: ``@IoaNNUwU``
r? ``@joboet``
This removes two minor OnceLock tests which test private methods. The
rest of the tests should be more than enough to catch mistakes in those
private methods. Also makes ReentrantLock::try_lock public. And finally
it makes the mpmc tests actually run.
std: allow after-main use of synchronization primitives
By creating an unnamed thread handle when the actual one has already been destroyed, synchronization primitives using thread parking can be used even outside the Rust runtime.
This also fixes an inefficiency in the queue-based `RwLock`: if `thread::current` was not initialized yet, it will create a new handle on every parking attempt without initializing `thread::current`. The private `current_or_unnamed` function introduced here fixes this.
By creating an unnamed thread handle when the actual one has already been destroyed, synchronization primitives using thread parking can be used even outside the Rust runtime.
This also fixes an inefficiency in the queue-based `RwLock`: if `thread::current` was not initialized yet, it will create a new handle on every parking attempt without initializing `thread::current`. The private `current_or_unnamed` function introduced here fixes this.
Rwlock downgrade
Tracking Issue: #128203
This PR adds a `downgrade` method for `RwLock` / `RwLockWriteGuard` on all currently supported platforms.
Outstanding questions:
- [x] ~~Does the `futex.rs` change affect performance at all? It doesn't seem like it will but we can't be certain until we bench it...~~
- [x] ~~Should the SOLID platform implementation [be ported over](https://github.com/rust-lang/rust/pull/128219#discussion_r1693470090) to the `queue.rs` implementation to allow it to support downgrades?~~
This commit fixes a memory ordering bug in the futex implementation
(`Relaxed` -> `Release` on `downgrade`).
This commit also removes a badly written test that deadlocked and
replaces it with a more reasonable test based on an already-tested
`downgrade` test from the parking-lot crate.
split up the first paragraph of doc comments for better summaries
used `./x clippy -Aclippy::all '-Wclippy::too_long_first_doc_paragraph' library/core library/alloc` to find these issues.
