diff --git a/src/libstd/thread/mod.rs b/src/libstd/thread/mod.rs index 9c15857edf6..5373bf273d4 100644 --- a/src/libstd/thread/mod.rs +++ b/src/libstd/thread/mod.rs @@ -96,41 +96,6 @@ //! The [`thread::current`] function is available even for threads not spawned //! by the APIs of this module. //! -//! ## Blocking support: park and unpark -//! -//! Every thread is equipped with some basic low-level blocking support, via the -//! [`thread::park`][`park`] function and [`thread::Thread::unpark()`][`unpark`] -//! method. [`park`] blocks the current thread, which can then be resumed from -//! another thread by calling the [`unpark`] method on the blocked thread's handle. -//! -//! Conceptually, each [`Thread`] handle has an associated token, which is -//! initially not present: -//! -//! * The [`thread::park`][`park`] function blocks the current thread unless or until -//! the token is available for its thread handle, at which point it atomically -//! consumes the token. It may also return *spuriously*, without consuming the -//! token. [`thread::park_timeout`] does the same, but allows specifying a -//! maximum time to block the thread for. -//! -//! * The [`unpark`] method on a [`Thread`] atomically makes the token available -//! if it wasn't already. -//! -//! In other words, each [`Thread`] acts a bit like a semaphore with initial count -//! 0, except that the semaphore is *saturating* (the count cannot go above 1), -//! and can return spuriously. -//! -//! The API is typically used by acquiring a handle to the current thread, -//! placing that handle in a shared data structure so that other threads can -//! find it, and then `park`ing. When some desired condition is met, another -//! thread calls [`unpark`] on the handle. -//! -//! The motivation for this design is twofold: -//! -//! * It avoids the need to allocate mutexes and condvars when building new -//! synchronization primitives; the threads already provide basic blocking/signaling. -//! -//! * It can be implemented very efficiently on many platforms. -//! //! ## Thread-local storage //! //! This module also provides an implementation of thread-local storage for Rust @@ -547,23 +512,71 @@ pub fn sleep(dur: Duration) { /// Blocks unless or until the current thread's token is made available. /// -/// Every thread is equipped with some basic low-level blocking support, via -/// the `park()` function and the [`unpark`][unpark] method. These can be -/// used as a more CPU-efficient implementation of a spinlock. -/// -/// [unpark]: struct.Thread.html#method.unpark -/// -/// The API is typically used by acquiring a handle to the current thread, -/// placing that handle in a shared data structure so that other threads can -/// find it, and then parking (in a loop with a check for the token actually -/// being acquired). -/// /// A call to `park` does not guarantee that the thread will remain parked /// forever, and callers should be prepared for this possibility. /// -/// See the [module documentation][thread] for more detail. +/// # park and unpark /// -/// [thread]: index.html +/// Every thread is equipped with some basic low-level blocking support, via the +/// [`thread::park`][`park`] function and [`thread::Thread::unpark()`][`unpark`] +/// method. [`park`] blocks the current thread, which can then be resumed from +/// another thread by calling the [`unpark`] method on the blocked thread's +/// handle. +/// +/// Conceptually, each [`Thread`] handle has an associated token, which is +/// initially not present: +/// +/// * The [`thread::park`][`park`] function blocks the current thread unless or +/// until the token is available for its thread handle, at which point it +/// atomically consumes the token. It may also return *spuriously*, without +/// consuming the token. [`thread::park_timeout`] does the same, but allows +/// specifying a maximum time to block the thread for. +/// +/// * The [`unpark`] method on a [`Thread`] atomically makes the token available +/// if it wasn't already. +/// +/// In other words, each [`Thread`] acts a bit like a spinlock that can be +/// locked and unlocked using `park` and `unpark`. +/// +/// The API is typically used by acquiring a handle to the current thread, +/// placing that handle in a shared data structure so that other threads can +/// find it, and then `park`ing. When some desired condition is met, another +/// thread calls [`unpark`] on the handle. +/// +/// The motivation for this design is twofold: +/// +/// * It avoids the need to allocate mutexes and condvars when building new +/// synchronization primitives; the threads already provide basic +/// blocking/signaling. +/// +/// * It can be implemented very efficiently on many platforms. +/// +/// # Examples +/// +/// ``` +/// use std::thread; +/// +/// let parked_thread = thread::Builder::new() +/// .spawn(|| { +/// println!("Parking thread"); +/// thread::park(); +/// println!("Thread unparked"); +/// }) +/// .unwrap(); +/// +/// // Let some time pass for the thread to be spawned. +/// thread::sleep(Duration::from_millis(10)); +/// +/// println!("Unpark the thread"); +/// parked_thread.thread().unpark(); +/// +/// parked_thread.join().unwrap(); +/// ``` +/// +/// [`Thread`]: ../../std/thread/struct.Thread.html +/// [`park`]: ../../std/thread/fn.park.html +/// [`unpark`]: ../../std/thread/struct.Thread.html#method.unpark +/// [`thread::park_timeout`]: ../../std/thread/fn.park_timeout.html // // The implementation currently uses the trivial strategy of a Mutex+Condvar // with wakeup flag, which does not actually allow spurious wakeups. In the @@ -591,11 +604,10 @@ pub fn park() { /// preemption or platform differences that may not cause the maximum /// amount of time waited to be precisely `ms` long. /// -/// See the [module documentation][thread] for more detail. +/// See the [park documentation][park] for more detail. /// -/// [thread]: index.html /// [park_timeout]: fn.park_timeout.html -/// [park]: fn.park.html +/// [park]: ../../std/thread/fn.park.html #[stable(feature = "rust1", since = "1.0.0")] #[rustc_deprecated(since = "1.6.0", reason = "replaced by `std::thread::park_timeout`")] pub fn park_timeout_ms(ms: u32) { @@ -611,7 +623,7 @@ pub fn park_timeout_ms(ms: u32) { /// preemption or platform differences that may not cause the maximum /// amount of time waited to be precisely `dur` long. /// -/// See the [module doc][thread] for more detail. +/// See the [park dococumentation][park] for more details. /// /// # Platform behavior /// @@ -637,7 +649,6 @@ pub fn park_timeout_ms(ms: u32) { /// } /// ``` /// -/// [thread]: index.html /// [park]: fn.park.html #[stable(feature = "park_timeout", since = "1.4.0")] pub fn park_timeout(dur: Duration) { @@ -772,7 +783,7 @@ impl Thread { /// the [`park()`][park] function and the `unpark()` method. These can be /// used as a more CPU-efficient implementation of a spinlock. /// - /// See the [module doc][thread] for more detail. + /// See the [park documentation][park] for more details. /// /// # Examples /// @@ -796,7 +807,6 @@ impl Thread { /// parked_thread.join().unwrap(); /// ``` /// - /// [thread]: index.html /// [park]: fn.park.html #[stable(feature = "rust1", since = "1.0.0")] pub fn unpark(&self) {