The algorithm backing `AtomicWaker` effectively uses a spin lock backed
by notifying & yielding the current task. This adds a `spin_lock_hint`
annotation to cover this case.
While, in practice, the omission of `spin_lock_hint` would not cause
problems, there are platforms that do not handle spin locks very well
and could enter a deadlock in pathological cases.
This adds `Barrier` to `tokio-sync`, which is an asynchronous alternative to [`std::sync::Barrier`](https://doc.rust-lang.org/std/sync/struct.Barrier.html). It is a synchronization primitive that allows multiple futures to "rendezvous" at certain points in their execution.
This renames `Lock` to `Mutex`, and brings the API more in line with `std::sync::Mutex`.
In partcular, locking now only takes `&self`, with the expectation that you place the `Mutex` in an `Arc` (or something similar) to share it between threads.
Fixes#1544.
Part of #1210.
Since `tokio_sync::oneshot` makes a `CausalCell::with_mut()` mutable
access in the `Inner::drop()`, we must use the instrumented
`loom::sync::Arc`.
Uncovered by carllerche/loom#42
A first pass at updating Tokio to use `std::future`.
Implementations of `Future` from the futures crate are updated to implement
`Future` from std. Implementations of `Stream` are moved to a feature flag.
This commits disables a number of crates that have not yet been updated.
This PR introduces `Lock`: A concurrency primitive built on top of `Semaphore` that provides a `Mutex`-like primitive that interacts nicely with futures. Specifically, `LockGuard` (in contrast to `MutexGuard`) does _not_ borrow the `Lock`, and can thus be passed into a future where it will later be unlocked.
This replaces #958, which attempted to introduce a less generic version. The primitive proposed there will instead live in [`async-lease`](https://github.com/jonhoo/async-lease).
A single-producer, multi-consumer channel that only retains the _last_ sent
value. Values are broadcasted out.
This channel is useful for watching for changes to a value from multiple
points in the code base (for example, changes to a configuration value).
Jon Gjengset