| // Copyright 2014 The Rust Project Developers. See the COPYRIGHT |
| // file at the top-level directory of this distribution and at |
| // http://rust-lang.org/COPYRIGHT. |
| // |
| // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or |
| // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license |
| // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your |
| // option. This file may not be copied, modified, or distributed |
| // except according to those terms. |
| |
| //! Native threads. |
| //! |
| //! ## The threading model |
| //! |
| //! An executing Rust program consists of a collection of native OS threads, |
| //! each with their own stack and local state. Threads can be named, and |
| //! provide some built-in support for low-level synchronization. |
| //! |
| //! Communication between threads can be done through |
| //! [channels], Rust's message-passing types, along with [other forms of thread |
| //! synchronization](../../std/sync/index.html) and shared-memory data |
| //! structures. In particular, types that are guaranteed to be |
| //! threadsafe are easily shared between threads using the |
| //! atomically-reference-counted container, [`Arc`]. |
| //! |
| //! Fatal logic errors in Rust cause *thread panic*, during which |
| //! a thread will unwind the stack, running destructors and freeing |
| //! owned resources. While not meant as a 'try/catch' mechanism, panics |
| //! in Rust can nonetheless be caught (unless compiling with `panic=abort`) with |
| //! [`catch_unwind`](../../std/panic/fn.catch_unwind.html) and recovered |
| //! from, or alternatively be resumed with |
| //! [`resume_unwind`](../../std/panic/fn.resume_unwind.html). If the panic |
| //! is not caught the thread will exit, but the panic may optionally be |
| //! detected from a different thread with [`join`]. If the main thread panics |
| //! without the panic being caught, the application will exit with a |
| //! non-zero exit code. |
| //! |
| //! When the main thread of a Rust program terminates, the entire program shuts |
| //! down, even if other threads are still running. However, this module provides |
| //! convenient facilities for automatically waiting for the termination of a |
| //! child thread (i.e., join). |
| //! |
| //! ## Spawning a thread |
| //! |
| //! A new thread can be spawned using the [`thread::spawn`][`spawn`] function: |
| //! |
| //! ```rust |
| //! use std::thread; |
| //! |
| //! thread::spawn(move || { |
| //! // some work here |
| //! }); |
| //! ``` |
| //! |
| //! In this example, the spawned thread is "detached" from the current |
| //! thread. This means that it can outlive its parent (the thread that spawned |
| //! it), unless this parent is the main thread. |
| //! |
| //! The parent thread can also wait on the completion of the child |
| //! thread; a call to [`spawn`] produces a [`JoinHandle`], which provides |
| //! a `join` method for waiting: |
| //! |
| //! ```rust |
| //! use std::thread; |
| //! |
| //! let child = thread::spawn(move || { |
| //! // some work here |
| //! }); |
| //! // some work here |
| //! let res = child.join(); |
| //! ``` |
| //! |
| //! The [`join`] method returns a [`thread::Result`] containing [`Ok`] of the final |
| //! value produced by the child thread, or [`Err`] of the value given to |
| //! a call to [`panic!`] if the child panicked. |
| //! |
| //! ## Configuring threads |
| //! |
| //! A new thread can be configured before it is spawned via the [`Builder`] type, |
| //! which currently allows you to set the name and stack size for the child thread: |
| //! |
| //! ```rust |
| //! # #![allow(unused_must_use)] |
| //! use std::thread; |
| //! |
| //! thread::Builder::new().name("child1".to_string()).spawn(move || { |
| //! println!("Hello, world!"); |
| //! }); |
| //! ``` |
| //! |
| //! ## The `Thread` type |
| //! |
| //! Threads are represented via the [`Thread`] type, which you can get in one of |
| //! two ways: |
| //! |
| //! * By spawning a new thread, e.g., using the [`thread::spawn`][`spawn`] |
| //! function, and calling [`thread`][`JoinHandle::thread`] on the [`JoinHandle`]. |
| //! * By requesting the current thread, using the [`thread::current`] function. |
| //! |
| //! The [`thread::current`] function is available even for threads not spawned |
| //! by the APIs of this module. |
| //! |
| //! ## Thread-local storage |
| //! |
| //! This module also provides an implementation of thread-local storage for Rust |
| //! programs. Thread-local storage is a method of storing data into a global |
| //! variable that each thread in the program will have its own copy of. |
| //! Threads do not share this data, so accesses do not need to be synchronized. |
| //! |
| //! A thread-local key owns the value it contains and will destroy the value when the |
| //! thread exits. It is created with the [`thread_local!`] macro and can contain any |
| //! value that is `'static` (no borrowed pointers). It provides an accessor function, |
| //! [`with`], that yields a shared reference to the value to the specified |
| //! closure. Thread-local keys allow only shared access to values, as there would be no |
| //! way to guarantee uniqueness if mutable borrows were allowed. Most values |
| //! will want to make use of some form of **interior mutability** through the |
| //! [`Cell`] or [`RefCell`] types. |
| //! |
| //! ## Naming threads |
| //! |
| //! Threads are able to have associated names for identification purposes. By default, spawned |
| //! threads are unnamed. To specify a name for a thread, build the thread with [`Builder`] and pass |
| //! the desired thread name to [`Builder::name`]. To retrieve the thread name from within the |
| //! thread, use [`Thread::name`]. A couple examples of where the name of a thread gets used: |
| //! |
| //! * If a panic occurs in a named thread, the thread name will be printed in the panic message. |
| //! * The thread name is provided to the OS where applicable (e.g., `pthread_setname_np` in |
| //! unix-like platforms). |
| //! |
| //! ## Stack size |
| //! |
| //! The default stack size for spawned threads is 2 MiB, though this particular stack size is |
| //! subject to change in the future. There are two ways to manually specify the stack size for |
| //! spawned threads: |
| //! |
| //! * Build the thread with [`Builder`] and pass the desired stack size to [`Builder::stack_size`]. |
| //! * Set the `RUST_MIN_STACK` environment variable to an integer representing the desired stack |
| //! size (in bytes). Note that setting [`Builder::stack_size`] will override this. |
| //! |
| //! Note that the stack size of the main thread is *not* determined by Rust. |
| //! |
| //! [channels]: ../../std/sync/mpsc/index.html |
| //! [`Arc`]: ../../std/sync/struct.Arc.html |
| //! [`spawn`]: ../../std/thread/fn.spawn.html |
| //! [`JoinHandle`]: ../../std/thread/struct.JoinHandle.html |
| //! [`JoinHandle::thread`]: ../../std/thread/struct.JoinHandle.html#method.thread |
| //! [`join`]: ../../std/thread/struct.JoinHandle.html#method.join |
| //! [`Result`]: ../../std/result/enum.Result.html |
| //! [`Ok`]: ../../std/result/enum.Result.html#variant.Ok |
| //! [`Err`]: ../../std/result/enum.Result.html#variant.Err |
| //! [`panic!`]: ../../std/macro.panic.html |
| //! [`Builder`]: ../../std/thread/struct.Builder.html |
| //! [`Builder::stack_size`]: ../../std/thread/struct.Builder.html#method.stack_size |
| //! [`Builder::name`]: ../../std/thread/struct.Builder.html#method.name |
| //! [`thread::current`]: ../../std/thread/fn.current.html |
| //! [`thread::Result`]: ../../std/thread/type.Result.html |
| //! [`Thread`]: ../../std/thread/struct.Thread.html |
| //! [`park`]: ../../std/thread/fn.park.html |
| //! [`unpark`]: ../../std/thread/struct.Thread.html#method.unpark |
| //! [`Thread::name`]: ../../std/thread/struct.Thread.html#method.name |
| //! [`thread::park_timeout`]: ../../std/thread/fn.park_timeout.html |
| //! [`Cell`]: ../cell/struct.Cell.html |
| //! [`RefCell`]: ../cell/struct.RefCell.html |
| //! [`thread_local!`]: ../macro.thread_local.html |
| //! [`with`]: struct.LocalKey.html#method.with |
| |
| #![stable(feature = "rust1", since = "1.0.0")] |
| |
| use any::Any; |
| use boxed::FnBox; |
| use cell::UnsafeCell; |
| use ffi::{CStr, CString}; |
| use fmt; |
| use io; |
| use mem; |
| use panic; |
| use panicking; |
| use str; |
| use sync::{Mutex, Condvar, Arc}; |
| use sync::atomic::AtomicUsize; |
| use sync::atomic::Ordering::SeqCst; |
| use sys::thread as imp; |
| use sys_common::mutex; |
| use sys_common::thread_info; |
| use sys_common::thread; |
| use sys_common::{AsInner, IntoInner}; |
| use time::Duration; |
| |
| //////////////////////////////////////////////////////////////////////////////// |
| // Thread-local storage |
| //////////////////////////////////////////////////////////////////////////////// |
| |
| #[macro_use] mod local; |
| |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub use self::local::{LocalKey, AccessError}; |
| |
| // The types used by the thread_local! macro to access TLS keys. Note that there |
| // are two types, the "OS" type and the "fast" type. The OS thread local key |
| // type is accessed via platform-specific API calls and is slow, while the fast |
| // key type is accessed via code generated via LLVM, where TLS keys are set up |
| // by the elf linker. Note that the OS TLS type is always available: on macOS |
| // the standard library is compiled with support for older platform versions |
| // where fast TLS was not available; end-user code is compiled with fast TLS |
| // where available, but both are needed. |
| |
| #[unstable(feature = "libstd_thread_internals", issue = "0")] |
| #[cfg(all(target_arch = "wasm32", not(target_feature = "atomics")))] |
| #[doc(hidden)] pub use self::local::statik::Key as __StaticLocalKeyInner; |
| #[unstable(feature = "libstd_thread_internals", issue = "0")] |
| #[cfg(target_thread_local)] |
| #[doc(hidden)] pub use self::local::fast::Key as __FastLocalKeyInner; |
| #[unstable(feature = "libstd_thread_internals", issue = "0")] |
| #[doc(hidden)] pub use self::local::os::Key as __OsLocalKeyInner; |
| |
| //////////////////////////////////////////////////////////////////////////////// |
| // Builder |
| //////////////////////////////////////////////////////////////////////////////// |
| |
| /// Thread factory, which can be used in order to configure the properties of |
| /// a new thread. |
| /// |
| /// Methods can be chained on it in order to configure it. |
| /// |
| /// The two configurations available are: |
| /// |
| /// - [`name`]: specifies an [associated name for the thread][naming-threads] |
| /// - [`stack_size`]: specifies the [desired stack size for the thread][stack-size] |
| /// |
| /// The [`spawn`] method will take ownership of the builder and create an |
| /// [`io::Result`] to the thread handle with the given configuration. |
| /// |
| /// The [`thread::spawn`] free function uses a `Builder` with default |
| /// configuration and [`unwrap`]s its return value. |
| /// |
| /// You may want to use [`spawn`] instead of [`thread::spawn`], when you want |
| /// to recover from a failure to launch a thread, indeed the free function will |
| /// panic where the `Builder` method will return a [`io::Result`]. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use std::thread; |
| /// |
| /// let builder = thread::Builder::new(); |
| /// |
| /// let handler = builder.spawn(|| { |
| /// // thread code |
| /// }).unwrap(); |
| /// |
| /// handler.join().unwrap(); |
| /// ``` |
| /// |
| /// [`thread::spawn`]: ../../std/thread/fn.spawn.html |
| /// [`stack_size`]: ../../std/thread/struct.Builder.html#method.stack_size |
| /// [`name`]: ../../std/thread/struct.Builder.html#method.name |
| /// [`spawn`]: ../../std/thread/struct.Builder.html#method.spawn |
| /// [`io::Result`]: ../../std/io/type.Result.html |
| /// [`unwrap`]: ../../std/result/enum.Result.html#method.unwrap |
| /// [naming-threads]: ./index.html#naming-threads |
| /// [stack-size]: ./index.html#stack-size |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[derive(Debug)] |
| pub struct Builder { |
| // A name for the thread-to-be, for identification in panic messages |
| name: Option<String>, |
| // The size of the stack for the spawned thread in bytes |
| stack_size: Option<usize>, |
| } |
| |
| impl Builder { |
| /// Generates the base configuration for spawning a thread, from which |
| /// configuration methods can be chained. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use std::thread; |
| /// |
| /// let builder = thread::Builder::new() |
| /// .name("foo".into()) |
| /// .stack_size(10); |
| /// |
| /// let handler = builder.spawn(|| { |
| /// // thread code |
| /// }).unwrap(); |
| /// |
| /// handler.join().unwrap(); |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub fn new() -> Builder { |
| Builder { |
| name: None, |
| stack_size: None, |
| } |
| } |
| |
| /// Names the thread-to-be. Currently the name is used for identification |
| /// only in panic messages. |
| /// |
| /// The name must not contain null bytes (`\0`). |
| /// |
| /// For more information about named threads, see |
| /// [this module-level documentation][naming-threads]. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use std::thread; |
| /// |
| /// let builder = thread::Builder::new() |
| /// .name("foo".into()); |
| /// |
| /// let handler = builder.spawn(|| { |
| /// assert_eq!(thread::current().name(), Some("foo")) |
| /// }).unwrap(); |
| /// |
| /// handler.join().unwrap(); |
| /// ``` |
| /// |
| /// [naming-threads]: ./index.html#naming-threads |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub fn name(mut self, name: String) -> Builder { |
| self.name = Some(name); |
| self |
| } |
| |
| /// Sets the size of the stack (in bytes) for the new thread. |
| /// |
| /// The actual stack size may be greater than this value if |
| /// the platform specifies a minimal stack size. |
| /// |
| /// For more information about the stack size for threads, see |
| /// [this module-level documentation][stack-size]. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use std::thread; |
| /// |
| /// let builder = thread::Builder::new().stack_size(32 * 1024); |
| /// ``` |
| /// |
| /// [stack-size]: ./index.html#stack-size |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub fn stack_size(mut self, size: usize) -> Builder { |
| self.stack_size = Some(size); |
| self |
| } |
| |
| /// Spawns a new thread by taking ownership of the `Builder`, and returns an |
| /// [`io::Result`] to its [`JoinHandle`]. |
| /// |
| /// The spawned thread may outlive the caller (unless the caller thread |
| /// is the main thread; the whole process is terminated when the main |
| /// thread finishes). The join handle can be used to block on |
| /// termination of the child thread, including recovering its panics. |
| /// |
| /// For a more complete documentation see [`thread::spawn`][`spawn`]. |
| /// |
| /// # Errors |
| /// |
| /// Unlike the [`spawn`] free function, this method yields an |
| /// [`io::Result`] to capture any failure to create the thread at |
| /// the OS level. |
| /// |
| /// [`spawn`]: ../../std/thread/fn.spawn.html |
| /// [`io::Result`]: ../../std/io/type.Result.html |
| /// [`JoinHandle`]: ../../std/thread/struct.JoinHandle.html |
| /// |
| /// # Panics |
| /// |
| /// Panics if a thread name was set and it contained null bytes. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use std::thread; |
| /// |
| /// let builder = thread::Builder::new(); |
| /// |
| /// let handler = builder.spawn(|| { |
| /// // thread code |
| /// }).unwrap(); |
| /// |
| /// handler.join().unwrap(); |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub fn spawn<F, T>(self, f: F) -> io::Result<JoinHandle<T>> where |
| F: FnOnce() -> T, F: Send + 'static, T: Send + 'static |
| { |
| unsafe { self.spawn_unchecked(f) } |
| } |
| |
| /// Spawns a new thread without any lifetime restrictions by taking ownership |
| /// of the `Builder`, and returns an [`io::Result`] to its [`JoinHandle`]. |
| /// |
| /// The spawned thread may outlive the caller (unless the caller thread |
| /// is the main thread; the whole process is terminated when the main |
| /// thread finishes). The join handle can be used to block on |
| /// termination of the child thread, including recovering its panics. |
| /// |
| /// This method is identical to [`thread::Builder::spawn`][`Builder::spawn`], |
| /// except for the relaxed lifetime bounds, which render it unsafe. |
| /// For a more complete documentation see [`thread::spawn`][`spawn`]. |
| /// |
| /// # Errors |
| /// |
| /// Unlike the [`spawn`] free function, this method yields an |
| /// [`io::Result`] to capture any failure to create the thread at |
| /// the OS level. |
| /// |
| /// # Panics |
| /// |
| /// Panics if a thread name was set and it contained null bytes. |
| /// |
| /// # Safety |
| /// |
| /// The caller has to ensure that no references in the supplied thread closure |
| /// or its return type can outlive the spawned thread's lifetime. This can be |
| /// guaranteed in two ways: |
| /// |
| /// - ensure that [`join`][`JoinHandle::join`] is called before any referenced |
| /// data is dropped |
| /// - use only types with `'static` lifetime bounds, i.e., those with no or only |
| /// `'static` references (both [`thread::Builder::spawn`][`Builder::spawn`] |
| /// and [`thread::spawn`][`spawn`] enforce this property statically) |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// #![feature(thread_spawn_unchecked)] |
| /// use std::thread; |
| /// |
| /// let builder = thread::Builder::new(); |
| /// |
| /// let x = 1; |
| /// let thread_x = &x; |
| /// |
| /// let handler = unsafe { |
| /// builder.spawn_unchecked(move || { |
| /// println!("x = {}", *thread_x); |
| /// }).unwrap() |
| /// }; |
| /// |
| /// // caller has to ensure `join()` is called, otherwise |
| /// // it is possible to access freed memory if `x` gets |
| /// // dropped before the thread closure is executed! |
| /// handler.join().unwrap(); |
| /// ``` |
| /// |
| /// [`spawn`]: ../../std/thread/fn.spawn.html |
| /// [`Builder::spawn`]: ../../std/thread/struct.Builder.html#method.spawn |
| /// [`io::Result`]: ../../std/io/type.Result.html |
| /// [`JoinHandle`]: ../../std/thread/struct.JoinHandle.html |
| #[unstable(feature = "thread_spawn_unchecked", issue = "55132")] |
| pub unsafe fn spawn_unchecked<'a, F, T>(self, f: F) -> io::Result<JoinHandle<T>> where |
| F: FnOnce() -> T, F: Send + 'a, T: Send + 'a |
| { |
| let Builder { name, stack_size } = self; |
| |
| let stack_size = stack_size.unwrap_or_else(thread::min_stack); |
| |
| let my_thread = Thread::new(name); |
| let their_thread = my_thread.clone(); |
| |
| let my_packet : Arc<UnsafeCell<Option<Result<T>>>> |
| = Arc::new(UnsafeCell::new(None)); |
| let their_packet = my_packet.clone(); |
| |
| let main = move || { |
| if let Some(name) = their_thread.cname() { |
| imp::Thread::set_name(name); |
| } |
| |
| thread_info::set(imp::guard::current(), their_thread); |
| #[cfg(feature = "backtrace")] |
| let try_result = panic::catch_unwind(panic::AssertUnwindSafe(|| { |
| ::sys_common::backtrace::__rust_begin_short_backtrace(f) |
| })); |
| #[cfg(not(feature = "backtrace"))] |
| let try_result = panic::catch_unwind(panic::AssertUnwindSafe(f)); |
| *their_packet.get() = Some(try_result); |
| }; |
| |
| Ok(JoinHandle(JoinInner { |
| // `imp::Thread::new` takes a closure with a `'static` lifetime, since it's passed |
| // through FFI or otherwise used with low-level threading primitives that have no |
| // notion of or way to enforce lifetimes. |
| // |
| // As mentioned in the `Safety` section of this function's documentation, the caller of |
| // this function needs to guarantee that the passed-in lifetime is sufficiently long |
| // for the lifetime of the thread. |
| // |
| // Similarly, the `sys` implementation must guarantee that no references to the closure |
| // exist after the thread has terminated, which is signaled by `Thread::join` |
| // returning. |
| native: Some(imp::Thread::new( |
| stack_size, |
| mem::transmute::<Box<dyn FnBox() + 'a>, Box<dyn FnBox() + 'static>>(Box::new(main)) |
| )?), |
| thread: my_thread, |
| packet: Packet(my_packet), |
| })) |
| } |
| } |
| |
| //////////////////////////////////////////////////////////////////////////////// |
| // Free functions |
| //////////////////////////////////////////////////////////////////////////////// |
| |
| /// Spawns a new thread, returning a [`JoinHandle`] for it. |
| /// |
| /// The join handle will implicitly *detach* the child thread upon being |
| /// dropped. In this case, the child thread may outlive the parent (unless |
| /// the parent thread is the main thread; the whole process is terminated when |
| /// the main thread finishes). Additionally, the join handle provides a [`join`] |
| /// method that can be used to join the child thread. If the child thread |
| /// panics, [`join`] will return an [`Err`] containing the argument given to |
| /// [`panic`]. |
| /// |
| /// This will create a thread using default parameters of [`Builder`], if you |
| /// want to specify the stack size or the name of the thread, use this API |
| /// instead. |
| /// |
| /// As you can see in the signature of `spawn` there are two constraints on |
| /// both the closure given to `spawn` and its return value, let's explain them: |
| /// |
| /// - The `'static` constraint means that the closure and its return value |
| /// must have a lifetime of the whole program execution. The reason for this |
| /// is that threads can `detach` and outlive the lifetime they have been |
| /// created in. |
| /// Indeed if the thread, and by extension its return value, can outlive their |
| /// caller, we need to make sure that they will be valid afterwards, and since |
| /// we *can't* know when it will return we need to have them valid as long as |
| /// possible, that is until the end of the program, hence the `'static` |
| /// lifetime. |
| /// - The [`Send`] constraint is because the closure will need to be passed |
| /// *by value* from the thread where it is spawned to the new thread. Its |
| /// return value will need to be passed from the new thread to the thread |
| /// where it is `join`ed. |
| /// As a reminder, the [`Send`] marker trait expresses that it is safe to be |
| /// passed from thread to thread. [`Sync`] expresses that it is safe to have a |
| /// reference be passed from thread to thread. |
| /// |
| /// # Panics |
| /// |
| /// Panics if the OS fails to create a thread; use [`Builder::spawn`] |
| /// to recover from such errors. |
| /// |
| /// # Examples |
| /// |
| /// Creating a thread. |
| /// |
| /// ``` |
| /// use std::thread; |
| /// |
| /// let handler = thread::spawn(|| { |
| /// // thread code |
| /// }); |
| /// |
| /// handler.join().unwrap(); |
| /// ``` |
| /// |
| /// As mentioned in the module documentation, threads are usually made to |
| /// communicate using [`channels`], here is how it usually looks. |
| /// |
| /// This example also shows how to use `move`, in order to give ownership |
| /// of values to a thread. |
| /// |
| /// ``` |
| /// use std::thread; |
| /// use std::sync::mpsc::channel; |
| /// |
| /// let (tx, rx) = channel(); |
| /// |
| /// let sender = thread::spawn(move || { |
| /// tx.send("Hello, thread".to_owned()) |
| /// .expect("Unable to send on channel"); |
| /// }); |
| /// |
| /// let receiver = thread::spawn(move || { |
| /// let value = rx.recv().expect("Unable to receive from channel"); |
| /// println!("{}", value); |
| /// }); |
| /// |
| /// sender.join().expect("The sender thread has panicked"); |
| /// receiver.join().expect("The receiver thread has panicked"); |
| /// ``` |
| /// |
| /// A thread can also return a value through its [`JoinHandle`], you can use |
| /// this to make asynchronous computations (futures might be more appropriate |
| /// though). |
| /// |
| /// ``` |
| /// use std::thread; |
| /// |
| /// let computation = thread::spawn(|| { |
| /// // Some expensive computation. |
| /// 42 |
| /// }); |
| /// |
| /// let result = computation.join().unwrap(); |
| /// println!("{}", result); |
| /// ``` |
| /// |
| /// [`channels`]: ../../std/sync/mpsc/index.html |
| /// [`JoinHandle`]: ../../std/thread/struct.JoinHandle.html |
| /// [`join`]: ../../std/thread/struct.JoinHandle.html#method.join |
| /// [`Err`]: ../../std/result/enum.Result.html#variant.Err |
| /// [`panic`]: ../../std/macro.panic.html |
| /// [`Builder::spawn`]: ../../std/thread/struct.Builder.html#method.spawn |
| /// [`Builder`]: ../../std/thread/struct.Builder.html |
| /// [`Send`]: ../../std/marker/trait.Send.html |
| /// [`Sync`]: ../../std/marker/trait.Sync.html |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub fn spawn<F, T>(f: F) -> JoinHandle<T> where |
| F: FnOnce() -> T, F: Send + 'static, T: Send + 'static |
| { |
| Builder::new().spawn(f).unwrap() |
| } |
| |
| /// Gets a handle to the thread that invokes it. |
| /// |
| /// # Examples |
| /// |
| /// Getting a handle to the current thread with `thread::current()`: |
| /// |
| /// ``` |
| /// use std::thread; |
| /// |
| /// let handler = thread::Builder::new() |
| /// .name("named thread".into()) |
| /// .spawn(|| { |
| /// let handle = thread::current(); |
| /// assert_eq!(handle.name(), Some("named thread")); |
| /// }) |
| /// .unwrap(); |
| /// |
| /// handler.join().unwrap(); |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub fn current() -> Thread { |
| thread_info::current_thread().expect("use of std::thread::current() is not \ |
| possible after the thread's local \ |
| data has been destroyed") |
| } |
| |
| /// Cooperatively gives up a timeslice to the OS scheduler. |
| /// |
| /// This is used when the programmer knows that the thread will have nothing |
| /// to do for some time, and thus avoid wasting computing time. |
| /// |
| /// For example when polling on a resource, it is common to check that it is |
| /// available, and if not to yield in order to avoid busy waiting. |
| /// |
| /// Thus the pattern of `yield`ing after a failed poll is rather common when |
| /// implementing low-level shared resources or synchronization primitives. |
| /// |
| /// However programmers will usually prefer to use [`channel`]s, [`Condvar`]s, |
| /// [`Mutex`]es or [`join`] for their synchronization routines, as they avoid |
| /// thinking about thread scheduling. |
| /// |
| /// Note that [`channel`]s for example are implemented using this primitive. |
| /// Indeed when you call `send` or `recv`, which are blocking, they will yield |
| /// if the channel is not available. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use std::thread; |
| /// |
| /// thread::yield_now(); |
| /// ``` |
| /// |
| /// [`channel`]: ../../std/sync/mpsc/index.html |
| /// [`spawn`]: ../../std/thread/fn.spawn.html |
| /// [`join`]: ../../std/thread/struct.JoinHandle.html#method.join |
| /// [`Mutex`]: ../../std/sync/struct.Mutex.html |
| /// [`Condvar`]: ../../std/sync/struct.Condvar.html |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub fn yield_now() { |
| imp::Thread::yield_now() |
| } |
| |
| /// Determines whether the current thread is unwinding because of panic. |
| /// |
| /// A common use of this feature is to poison shared resources when writing |
| /// unsafe code, by checking `panicking` when the `drop` is called. |
| /// |
| /// This is usually not needed when writing safe code, as [`Mutex`es][Mutex] |
| /// already poison themselves when a thread panics while holding the lock. |
| /// |
| /// This can also be used in multithreaded applications, in order to send a |
| /// message to other threads warning that a thread has panicked (e.g., for |
| /// monitoring purposes). |
| /// |
| /// # Examples |
| /// |
| /// ```should_panic |
| /// use std::thread; |
| /// |
| /// struct SomeStruct; |
| /// |
| /// impl Drop for SomeStruct { |
| /// fn drop(&mut self) { |
| /// if thread::panicking() { |
| /// println!("dropped while unwinding"); |
| /// } else { |
| /// println!("dropped while not unwinding"); |
| /// } |
| /// } |
| /// } |
| /// |
| /// { |
| /// print!("a: "); |
| /// let a = SomeStruct; |
| /// } |
| /// |
| /// { |
| /// print!("b: "); |
| /// let b = SomeStruct; |
| /// panic!() |
| /// } |
| /// ``` |
| /// |
| /// [Mutex]: ../../std/sync/struct.Mutex.html |
| #[inline] |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub fn panicking() -> bool { |
| panicking::panicking() |
| } |
| |
| /// Puts the current thread to sleep for at least the specified amount of time. |
| /// |
| /// The thread may sleep longer than the duration specified due to scheduling |
| /// specifics or platform-dependent functionality. It will never sleep less. |
| /// |
| /// # Platform-specific behavior |
| /// |
| /// On Unix platforms, the underlying syscall may be interrupted by a |
| /// spurious wakeup or signal handler. To ensure the sleep occurs for at least |
| /// the specified duration, this function may invoke that system call multiple |
| /// times. |
| /// |
| /// # Examples |
| /// |
| /// ```no_run |
| /// use std::thread; |
| /// |
| /// // Let's sleep for 2 seconds: |
| /// thread::sleep_ms(2000); |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[rustc_deprecated(since = "1.6.0", reason = "replaced by `std::thread::sleep`")] |
| pub fn sleep_ms(ms: u32) { |
| sleep(Duration::from_millis(ms as u64)) |
| } |
| |
| /// Puts the current thread to sleep for at least the specified amount of time. |
| /// |
| /// The thread may sleep longer than the duration specified due to scheduling |
| /// specifics or platform-dependent functionality. It will never sleep less. |
| /// |
| /// # Platform-specific behavior |
| /// |
| /// On Unix platforms, the underlying syscall may be interrupted by a |
| /// spurious wakeup or signal handler. To ensure the sleep occurs for at least |
| /// the specified duration, this function may invoke that system call multiple |
| /// times. |
| /// Platforms which do not support nanosecond precision for sleeping will |
| /// have `dur` rounded up to the nearest granularity of time they can sleep for. |
| /// |
| /// # Examples |
| /// |
| /// ```no_run |
| /// use std::{thread, time}; |
| /// |
| /// let ten_millis = time::Duration::from_millis(10); |
| /// let now = time::Instant::now(); |
| /// |
| /// thread::sleep(ten_millis); |
| /// |
| /// assert!(now.elapsed() >= ten_millis); |
| /// ``` |
| #[stable(feature = "thread_sleep", since = "1.4.0")] |
| pub fn sleep(dur: Duration) { |
| imp::Thread::sleep(dur) |
| } |
| |
| // constants for park/unpark |
| const EMPTY: usize = 0; |
| const PARKED: usize = 1; |
| const NOTIFIED: usize = 2; |
| |
| /// Blocks unless or until the current thread's token is made available. |
| /// |
| /// A call to `park` does not guarantee that the thread will remain parked |
| /// forever, and callers should be prepared for this possibility. |
| /// |
| /// # 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. Because the token is initially absent, [`unpark`] |
| /// followed by [`park`] will result in the second call returning immediately. |
| /// |
| /// 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; |
| /// use std::time::Duration; |
| /// |
| /// 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)); |
| /// |
| /// // There is no race condition here, if `unpark` |
| /// // happens first, `park` will return immediately. |
| /// 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 |
| // future, this will be implemented in a more efficient way, perhaps along the lines of |
| // http://cr.openjdk.java.net/~stefank/6989984.1/raw_files/new/src/os/linux/vm/os_linux.cpp |
| // or futuxes, and in either case may allow spurious wakeups. |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub fn park() { |
| let thread = current(); |
| |
| // If we were previously notified then we consume this notification and |
| // return quickly. |
| if thread.inner.state.compare_exchange(NOTIFIED, EMPTY, SeqCst, SeqCst).is_ok() { |
| return |
| } |
| |
| // Otherwise we need to coordinate going to sleep |
| let mut m = thread.inner.lock.lock().unwrap(); |
| match thread.inner.state.compare_exchange(EMPTY, PARKED, SeqCst, SeqCst) { |
| Ok(_) => {} |
| Err(NOTIFIED) => { |
| // We must read here, even though we know it will be `NOTIFIED`. |
| // This is because `unpark` may have been called again since we read |
| // `NOTIFIED` in the `compare_exchange` above. We must perform an |
| // acquire operation that synchronizes with that `unpark` to observe |
| // any writes it made before the call to unpark. To do that we must |
| // read from the write it made to `state`. |
| let old = thread.inner.state.swap(EMPTY, SeqCst); |
| assert_eq!(old, NOTIFIED, "park state changed unexpectedly"); |
| return; |
| } // should consume this notification, so prohibit spurious wakeups in next park. |
| Err(_) => panic!("inconsistent park state"), |
| } |
| loop { |
| m = thread.inner.cvar.wait(m).unwrap(); |
| match thread.inner.state.compare_exchange(NOTIFIED, EMPTY, SeqCst, SeqCst) { |
| Ok(_) => return, // got a notification |
| Err(_) => {} // spurious wakeup, go back to sleep |
| } |
| } |
| } |
| |
| /// Use [`park_timeout`]. |
| /// |
| /// Blocks unless or until the current thread's token is made available or |
| /// the specified duration has been reached (may wake spuriously). |
| /// |
| /// The semantics of this function are equivalent to [`park`] except |
| /// that the thread will be blocked for roughly no longer than `dur`. This |
| /// method should not be used for precise timing due to anomalies such as |
| /// preemption or platform differences that may not cause the maximum |
| /// amount of time waited to be precisely `ms` long. |
| /// |
| /// See the [park documentation][`park`] for more detail. |
| /// |
| /// [`park_timeout`]: fn.park_timeout.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) { |
| park_timeout(Duration::from_millis(ms as u64)) |
| } |
| |
| /// Blocks unless or until the current thread's token is made available or |
| /// the specified duration has been reached (may wake spuriously). |
| /// |
| /// The semantics of this function are equivalent to [`park`][park] except |
| /// that the thread will be blocked for roughly no longer than `dur`. This |
| /// method should not be used for precise timing due to anomalies such as |
| /// preemption or platform differences that may not cause the maximum |
| /// amount of time waited to be precisely `dur` long. |
| /// |
| /// See the [park documentation][park] for more details. |
| /// |
| /// # Platform-specific behavior |
| /// |
| /// Platforms which do not support nanosecond precision for sleeping will have |
| /// `dur` rounded up to the nearest granularity of time they can sleep for. |
| /// |
| /// # Examples |
| /// |
| /// Waiting for the complete expiration of the timeout: |
| /// |
| /// ```rust,no_run |
| /// use std::thread::park_timeout; |
| /// use std::time::{Instant, Duration}; |
| /// |
| /// let timeout = Duration::from_secs(2); |
| /// let beginning_park = Instant::now(); |
| /// |
| /// let mut timeout_remaining = timeout; |
| /// loop { |
| /// park_timeout(timeout_remaining); |
| /// let elapsed = beginning_park.elapsed(); |
| /// if elapsed >= timeout { |
| /// break; |
| /// } |
| /// println!("restarting park_timeout after {:?}", elapsed); |
| /// timeout_remaining = timeout - elapsed; |
| /// } |
| /// ``` |
| /// |
| /// [park]: fn.park.html |
| #[stable(feature = "park_timeout", since = "1.4.0")] |
| pub fn park_timeout(dur: Duration) { |
| let thread = current(); |
| |
| // Like `park` above we have a fast path for an already-notified thread, and |
| // afterwards we start coordinating for a sleep. |
| // return quickly. |
| if thread.inner.state.compare_exchange(NOTIFIED, EMPTY, SeqCst, SeqCst).is_ok() { |
| return |
| } |
| let m = thread.inner.lock.lock().unwrap(); |
| match thread.inner.state.compare_exchange(EMPTY, PARKED, SeqCst, SeqCst) { |
| Ok(_) => {} |
| Err(NOTIFIED) => { |
| // We must read again here, see `park`. |
| let old = thread.inner.state.swap(EMPTY, SeqCst); |
| assert_eq!(old, NOTIFIED, "park state changed unexpectedly"); |
| return; |
| } // should consume this notification, so prohibit spurious wakeups in next park. |
| Err(_) => panic!("inconsistent park_timeout state"), |
| } |
| |
| // Wait with a timeout, and if we spuriously wake up or otherwise wake up |
| // from a notification we just want to unconditionally set the state back to |
| // empty, either consuming a notification or un-flagging ourselves as |
| // parked. |
| let (_m, _result) = thread.inner.cvar.wait_timeout(m, dur).unwrap(); |
| match thread.inner.state.swap(EMPTY, SeqCst) { |
| NOTIFIED => {} // got a notification, hurray! |
| PARKED => {} // no notification, alas |
| n => panic!("inconsistent park_timeout state: {}", n), |
| } |
| } |
| |
| //////////////////////////////////////////////////////////////////////////////// |
| // ThreadId |
| //////////////////////////////////////////////////////////////////////////////// |
| |
| /// A unique identifier for a running thread. |
| /// |
| /// A `ThreadId` is an opaque object that has a unique value for each thread |
| /// that creates one. `ThreadId`s are not guaranteed to correspond to a thread's |
| /// system-designated identifier. A `ThreadId` can be retrieved from the [`id`] |
| /// method on a [`Thread`]. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use std::thread; |
| /// |
| /// let other_thread = thread::spawn(|| { |
| /// thread::current().id() |
| /// }); |
| /// |
| /// let other_thread_id = other_thread.join().unwrap(); |
| /// assert!(thread::current().id() != other_thread_id); |
| /// ``` |
| /// |
| /// [`id`]: ../../std/thread/struct.Thread.html#method.id |
| /// [`Thread`]: ../../std/thread/struct.Thread.html |
| #[stable(feature = "thread_id", since = "1.19.0")] |
| #[derive(Eq, PartialEq, Clone, Copy, Hash, Debug)] |
| pub struct ThreadId(u64); |
| |
| impl ThreadId { |
| // Generate a new unique thread ID. |
| fn new() -> ThreadId { |
| // We never call `GUARD.init()`, so it is UB to attempt to |
| // acquire this mutex reentrantly! |
| static GUARD: mutex::Mutex = mutex::Mutex::new(); |
| static mut COUNTER: u64 = 0; |
| |
| unsafe { |
| let _guard = GUARD.lock(); |
| |
| // If we somehow use up all our bits, panic so that we're not |
| // covering up subtle bugs of IDs being reused. |
| if COUNTER == ::u64::MAX { |
| panic!("failed to generate unique thread ID: bitspace exhausted"); |
| } |
| |
| let id = COUNTER; |
| COUNTER += 1; |
| |
| ThreadId(id) |
| } |
| } |
| } |
| |
| //////////////////////////////////////////////////////////////////////////////// |
| // Thread |
| //////////////////////////////////////////////////////////////////////////////// |
| |
| /// The internal representation of a `Thread` handle |
| struct Inner { |
| name: Option<CString>, // Guaranteed to be UTF-8 |
| id: ThreadId, |
| |
| // state for thread park/unpark |
| state: AtomicUsize, |
| lock: Mutex<()>, |
| cvar: Condvar, |
| } |
| |
| #[derive(Clone)] |
| #[stable(feature = "rust1", since = "1.0.0")] |
| /// A handle to a thread. |
| /// |
| /// Threads are represented via the `Thread` type, which you can get in one of |
| /// two ways: |
| /// |
| /// * By spawning a new thread, e.g., using the [`thread::spawn`][`spawn`] |
| /// function, and calling [`thread`][`JoinHandle::thread`] on the |
| /// [`JoinHandle`]. |
| /// * By requesting the current thread, using the [`thread::current`] function. |
| /// |
| /// The [`thread::current`] function is available even for threads not spawned |
| /// by the APIs of this module. |
| /// |
| /// There is usually no need to create a `Thread` struct yourself, one |
| /// should instead use a function like `spawn` to create new threads, see the |
| /// docs of [`Builder`] and [`spawn`] for more details. |
| /// |
| /// [`Builder`]: ../../std/thread/struct.Builder.html |
| /// [`JoinHandle::thread`]: ../../std/thread/struct.JoinHandle.html#method.thread |
| /// [`JoinHandle`]: ../../std/thread/struct.JoinHandle.html |
| /// [`thread::current`]: ../../std/thread/fn.current.html |
| /// [`spawn`]: ../../std/thread/fn.spawn.html |
| |
| pub struct Thread { |
| inner: Arc<Inner>, |
| } |
| |
| impl Thread { |
| // Used only internally to construct a thread object without spawning |
| // Panics if the name contains nuls. |
| pub(crate) fn new(name: Option<String>) -> Thread { |
| let cname = name.map(|n| { |
| CString::new(n).expect("thread name may not contain interior null bytes") |
| }); |
| Thread { |
| inner: Arc::new(Inner { |
| name: cname, |
| id: ThreadId::new(), |
| state: AtomicUsize::new(EMPTY), |
| lock: Mutex::new(()), |
| cvar: Condvar::new(), |
| }) |
| } |
| } |
| |
| /// Atomically makes the handle's token available if it is not already. |
| /// |
| /// Every thread is equipped with some basic low-level blocking support, via |
| /// the [`park`][park] function and the `unpark()` method. These can be |
| /// used as a more CPU-efficient implementation of a spinlock. |
| /// |
| /// See the [park documentation][park] for more details. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use std::thread; |
| /// use std::time::Duration; |
| /// |
| /// 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(); |
| /// ``` |
| /// |
| /// [park]: fn.park.html |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub fn unpark(&self) { |
| // To ensure the unparked thread will observe any writes we made |
| // before this call, we must perform a release operation that `park` |
| // can synchronize with. To do that we must write `NOTIFIED` even if |
| // `state` is already `NOTIFIED`. That is why this must be a swap |
| // rather than a compare-and-swap that returns if it reads `NOTIFIED` |
| // on failure. |
| match self.inner.state.swap(NOTIFIED, SeqCst) { |
| EMPTY => return, // no one was waiting |
| NOTIFIED => return, // already unparked |
| PARKED => {} // gotta go wake someone up |
| _ => panic!("inconsistent state in unpark"), |
| } |
| |
| // There is a period between when the parked thread sets `state` to |
| // `PARKED` (or last checked `state` in the case of a spurious wake |
| // up) and when it actually waits on `cvar`. If we were to notify |
| // during this period it would be ignored and then when the parked |
| // thread went to sleep it would never wake up. Fortunately, it has |
| // `lock` locked at this stage so we can acquire `lock` to wait until |
| // it is ready to receive the notification. |
| // |
| // Releasing `lock` before the call to `notify_one` means that when the |
| // parked thread wakes it doesn't get woken only to have to wait for us |
| // to release `lock`. |
| drop(self.inner.lock.lock().unwrap()); |
| self.inner.cvar.notify_one() |
| } |
| |
| /// Gets the thread's unique identifier. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use std::thread; |
| /// |
| /// let other_thread = thread::spawn(|| { |
| /// thread::current().id() |
| /// }); |
| /// |
| /// let other_thread_id = other_thread.join().unwrap(); |
| /// assert!(thread::current().id() != other_thread_id); |
| /// ``` |
| #[stable(feature = "thread_id", since = "1.19.0")] |
| pub fn id(&self) -> ThreadId { |
| self.inner.id |
| } |
| |
| /// Gets the thread's name. |
| /// |
| /// For more information about named threads, see |
| /// [this module-level documentation][naming-threads]. |
| /// |
| /// # Examples |
| /// |
| /// Threads by default have no name specified: |
| /// |
| /// ``` |
| /// use std::thread; |
| /// |
| /// let builder = thread::Builder::new(); |
| /// |
| /// let handler = builder.spawn(|| { |
| /// assert!(thread::current().name().is_none()); |
| /// }).unwrap(); |
| /// |
| /// handler.join().unwrap(); |
| /// ``` |
| /// |
| /// Thread with a specified name: |
| /// |
| /// ``` |
| /// use std::thread; |
| /// |
| /// let builder = thread::Builder::new() |
| /// .name("foo".into()); |
| /// |
| /// let handler = builder.spawn(|| { |
| /// assert_eq!(thread::current().name(), Some("foo")) |
| /// }).unwrap(); |
| /// |
| /// handler.join().unwrap(); |
| /// ``` |
| /// |
| /// [naming-threads]: ./index.html#naming-threads |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub fn name(&self) -> Option<&str> { |
| self.cname().map(|s| unsafe { str::from_utf8_unchecked(s.to_bytes()) } ) |
| } |
| |
| fn cname(&self) -> Option<&CStr> { |
| self.inner.name.as_ref().map(|s| &**s) |
| } |
| } |
| |
| #[stable(feature = "rust1", since = "1.0.0")] |
| impl fmt::Debug for Thread { |
| fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { |
| fmt::Debug::fmt(&self.name(), f) |
| } |
| } |
| |
| //////////////////////////////////////////////////////////////////////////////// |
| // JoinHandle |
| //////////////////////////////////////////////////////////////////////////////// |
| |
| /// A specialized [`Result`] type for threads. |
| /// |
| /// Indicates the manner in which a thread exited. |
| /// |
| /// A thread that completes without panicking is considered to exit successfully. |
| /// |
| /// # Examples |
| /// |
| /// ```no_run |
| /// use std::thread; |
| /// use std::fs; |
| /// |
| /// fn copy_in_thread() -> thread::Result<()> { |
| /// thread::spawn(move || { fs::copy("foo.txt", "bar.txt").unwrap(); }).join() |
| /// } |
| /// |
| /// fn main() { |
| /// match copy_in_thread() { |
| /// Ok(_) => println!("this is fine"), |
| /// Err(_) => println!("thread panicked"), |
| /// } |
| /// } |
| /// ``` |
| /// |
| /// [`Result`]: ../../std/result/enum.Result.html |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub type Result<T> = ::result::Result<T, Box<dyn Any + Send + 'static>>; |
| |
| // This packet is used to communicate the return value between the child thread |
| // and the parent thread. Memory is shared through the `Arc` within and there's |
| // no need for a mutex here because synchronization happens with `join()` (the |
| // parent thread never reads this packet until the child has exited). |
| // |
| // This packet itself is then stored into a `JoinInner` which in turns is placed |
| // in `JoinHandle` and `JoinGuard`. Due to the usage of `UnsafeCell` we need to |
| // manually worry about impls like Send and Sync. The type `T` should |
| // already always be Send (otherwise the thread could not have been created) and |
| // this type is inherently Sync because no methods take &self. Regardless, |
| // however, we add inheriting impls for Send/Sync to this type to ensure it's |
| // Send/Sync and that future modifications will still appropriately classify it. |
| struct Packet<T>(Arc<UnsafeCell<Option<Result<T>>>>); |
| |
| unsafe impl<T: Send> Send for Packet<T> {} |
| unsafe impl<T: Sync> Sync for Packet<T> {} |
| |
| /// Inner representation for JoinHandle |
| struct JoinInner<T> { |
| native: Option<imp::Thread>, |
| thread: Thread, |
| packet: Packet<T>, |
| } |
| |
| impl<T> JoinInner<T> { |
| fn join(&mut self) -> Result<T> { |
| self.native.take().unwrap().join(); |
| unsafe { |
| (*self.packet.0.get()).take().unwrap() |
| } |
| } |
| } |
| |
| /// An owned permission to join on a thread (block on its termination). |
| /// |
| /// A `JoinHandle` *detaches* the associated thread when it is dropped, which |
| /// means that there is no longer any handle to thread and no way to `join` |
| /// on it. |
| /// |
| /// Due to platform restrictions, it is not possible to [`Clone`] this |
| /// handle: the ability to join a thread is a uniquely-owned permission. |
| /// |
| /// This `struct` is created by the [`thread::spawn`] function and the |
| /// [`thread::Builder::spawn`] method. |
| /// |
| /// # Examples |
| /// |
| /// Creation from [`thread::spawn`]: |
| /// |
| /// ``` |
| /// use std::thread; |
| /// |
| /// let join_handle: thread::JoinHandle<_> = thread::spawn(|| { |
| /// // some work here |
| /// }); |
| /// ``` |
| /// |
| /// Creation from [`thread::Builder::spawn`]: |
| /// |
| /// ``` |
| /// use std::thread; |
| /// |
| /// let builder = thread::Builder::new(); |
| /// |
| /// let join_handle: thread::JoinHandle<_> = builder.spawn(|| { |
| /// // some work here |
| /// }).unwrap(); |
| /// ``` |
| /// |
| /// Child being detached and outliving its parent: |
| /// |
| /// ```no_run |
| /// use std::thread; |
| /// use std::time::Duration; |
| /// |
| /// let original_thread = thread::spawn(|| { |
| /// let _detached_thread = thread::spawn(|| { |
| /// // Here we sleep to make sure that the first thread returns before. |
| /// thread::sleep(Duration::from_millis(10)); |
| /// // This will be called, even though the JoinHandle is dropped. |
| /// println!("♫ Still alive ♫"); |
| /// }); |
| /// }); |
| /// |
| /// original_thread.join().expect("The thread being joined has panicked"); |
| /// println!("Original thread is joined."); |
| /// |
| /// // We make sure that the new thread has time to run, before the main |
| /// // thread returns. |
| /// |
| /// thread::sleep(Duration::from_millis(1000)); |
| /// ``` |
| /// |
| /// [`Clone`]: ../../std/clone/trait.Clone.html |
| /// [`thread::spawn`]: fn.spawn.html |
| /// [`thread::Builder::spawn`]: struct.Builder.html#method.spawn |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub struct JoinHandle<T>(JoinInner<T>); |
| |
| #[stable(feature = "joinhandle_impl_send_sync", since = "1.29.0")] |
| unsafe impl<T> Send for JoinHandle<T> {} |
| #[stable(feature = "joinhandle_impl_send_sync", since = "1.29.0")] |
| unsafe impl<T> Sync for JoinHandle<T> {} |
| |
| impl<T> JoinHandle<T> { |
| /// Extracts a handle to the underlying thread. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use std::thread; |
| /// |
| /// let builder = thread::Builder::new(); |
| /// |
| /// let join_handle: thread::JoinHandle<_> = builder.spawn(|| { |
| /// // some work here |
| /// }).unwrap(); |
| /// |
| /// let thread = join_handle.thread(); |
| /// println!("thread id: {:?}", thread.id()); |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub fn thread(&self) -> &Thread { |
| &self.0.thread |
| } |
| |
| /// Waits for the associated thread to finish. |
| /// |
| /// In terms of [atomic memory orderings], the completion of the associated |
| /// thread synchronizes with this function returning. In other words, all |
| /// operations performed by that thread are ordered before all |
| /// operations that happen after `join` returns. |
| /// |
| /// If the child thread panics, [`Err`] is returned with the parameter given |
| /// to [`panic`]. |
| /// |
| /// [`Err`]: ../../std/result/enum.Result.html#variant.Err |
| /// [`panic`]: ../../std/macro.panic.html |
| /// [atomic memory orderings]: ../../std/sync/atomic/index.html |
| /// |
| /// # Panics |
| /// |
| /// This function may panic on some platforms if a thread attempts to join |
| /// itself or otherwise may create a deadlock with joining threads. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use std::thread; |
| /// |
| /// let builder = thread::Builder::new(); |
| /// |
| /// let join_handle: thread::JoinHandle<_> = builder.spawn(|| { |
| /// // some work here |
| /// }).unwrap(); |
| /// join_handle.join().expect("Couldn't join on the associated thread"); |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub fn join(mut self) -> Result<T> { |
| self.0.join() |
| } |
| } |
| |
| impl<T> AsInner<imp::Thread> for JoinHandle<T> { |
| fn as_inner(&self) -> &imp::Thread { self.0.native.as_ref().unwrap() } |
| } |
| |
| impl<T> IntoInner<imp::Thread> for JoinHandle<T> { |
| fn into_inner(self) -> imp::Thread { self.0.native.unwrap() } |
| } |
| |
| #[stable(feature = "std_debug", since = "1.16.0")] |
| impl<T> fmt::Debug for JoinHandle<T> { |
| fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { |
| f.pad("JoinHandle { .. }") |
| } |
| } |
| |
| fn _assert_sync_and_send() { |
| fn _assert_both<T: Send + Sync>() {} |
| _assert_both::<JoinHandle<()>>(); |
| _assert_both::<Thread>(); |
| } |
| |
| //////////////////////////////////////////////////////////////////////////////// |
| // Tests |
| //////////////////////////////////////////////////////////////////////////////// |
| |
| #[cfg(all(test, not(target_os = "emscripten")))] |
| mod tests { |
| use any::Any; |
| use sync::mpsc::{channel, Sender}; |
| use result; |
| use super::{Builder}; |
| use thread; |
| use time::Duration; |
| use u32; |
| |
| // !!! These tests are dangerous. If something is buggy, they will hang, !!! |
| // !!! instead of exiting cleanly. This might wedge the buildbots. !!! |
| |
| #[test] |
| fn test_unnamed_thread() { |
| thread::spawn(move|| { |
| assert!(thread::current().name().is_none()); |
| }).join().ok().unwrap(); |
| } |
| |
| #[test] |
| fn test_named_thread() { |
| Builder::new().name("ada lovelace".to_string()).spawn(move|| { |
| assert!(thread::current().name().unwrap() == "ada lovelace".to_string()); |
| }).unwrap().join().unwrap(); |
| } |
| |
| #[test] |
| #[should_panic] |
| fn test_invalid_named_thread() { |
| let _ = Builder::new().name("ada l\0velace".to_string()).spawn(|| {}); |
| } |
| |
| #[test] |
| fn test_run_basic() { |
| let (tx, rx) = channel(); |
| thread::spawn(move|| { |
| tx.send(()).unwrap(); |
| }); |
| rx.recv().unwrap(); |
| } |
| |
| #[test] |
| fn test_join_panic() { |
| match thread::spawn(move|| { |
| panic!() |
| }).join() { |
| result::Result::Err(_) => (), |
| result::Result::Ok(()) => panic!() |
| } |
| } |
| |
| #[test] |
| fn test_spawn_sched() { |
| let (tx, rx) = channel(); |
| |
| fn f(i: i32, tx: Sender<()>) { |
| let tx = tx.clone(); |
| thread::spawn(move|| { |
| if i == 0 { |
| tx.send(()).unwrap(); |
| } else { |
| f(i - 1, tx); |
| } |
| }); |
| |
| } |
| f(10, tx); |
| rx.recv().unwrap(); |
| } |
| |
| #[test] |
| fn test_spawn_sched_childs_on_default_sched() { |
| let (tx, rx) = channel(); |
| |
| thread::spawn(move|| { |
| thread::spawn(move|| { |
| tx.send(()).unwrap(); |
| }); |
| }); |
| |
| rx.recv().unwrap(); |
| } |
| |
| fn avoid_copying_the_body<F>(spawnfn: F) where F: FnOnce(Box<dyn Fn() + Send>) { |
| let (tx, rx) = channel(); |
| |
| let x: Box<_> = box 1; |
| let x_in_parent = (&*x) as *const i32 as usize; |
| |
| spawnfn(Box::new(move|| { |
| let x_in_child = (&*x) as *const i32 as usize; |
| tx.send(x_in_child).unwrap(); |
| })); |
| |
| let x_in_child = rx.recv().unwrap(); |
| assert_eq!(x_in_parent, x_in_child); |
| } |
| |
| #[test] |
| fn test_avoid_copying_the_body_spawn() { |
| avoid_copying_the_body(|v| { |
| thread::spawn(move || v()); |
| }); |
| } |
| |
| #[test] |
| fn test_avoid_copying_the_body_thread_spawn() { |
| avoid_copying_the_body(|f| { |
| thread::spawn(move|| { |
| f(); |
| }); |
| }) |
| } |
| |
| #[test] |
| fn test_avoid_copying_the_body_join() { |
| avoid_copying_the_body(|f| { |
| let _ = thread::spawn(move|| { |
| f() |
| }).join(); |
| }) |
| } |
| |
| #[test] |
| fn test_child_doesnt_ref_parent() { |
| // If the child refcounts the parent thread, this will stack overflow when |
| // climbing the thread tree to dereference each ancestor. (See #1789) |
| // (well, it would if the constant were 8000+ - I lowered it to be more |
| // valgrind-friendly. try this at home, instead..!) |
| const GENERATIONS: u32 = 16; |
| fn child_no(x: u32) -> Box<dyn Fn() + Send> { |
| return Box::new(move|| { |
| if x < GENERATIONS { |
| thread::spawn(move|| child_no(x+1)()); |
| } |
| }); |
| } |
| thread::spawn(|| child_no(0)()); |
| } |
| |
| #[test] |
| fn test_simple_newsched_spawn() { |
| thread::spawn(move || {}); |
| } |
| |
| #[test] |
| fn test_try_panic_message_static_str() { |
| match thread::spawn(move|| { |
| panic!("static string"); |
| }).join() { |
| Err(e) => { |
| type T = &'static str; |
| assert!(e.is::<T>()); |
| assert_eq!(*e.downcast::<T>().unwrap(), "static string"); |
| } |
| Ok(()) => panic!() |
| } |
| } |
| |
| #[test] |
| fn test_try_panic_message_owned_str() { |
| match thread::spawn(move|| { |
| panic!("owned string".to_string()); |
| }).join() { |
| Err(e) => { |
| type T = String; |
| assert!(e.is::<T>()); |
| assert_eq!(*e.downcast::<T>().unwrap(), "owned string".to_string()); |
| } |
| Ok(()) => panic!() |
| } |
| } |
| |
| #[test] |
| fn test_try_panic_message_any() { |
| match thread::spawn(move|| { |
| panic!(box 413u16 as Box<dyn Any + Send>); |
| }).join() { |
| Err(e) => { |
| type T = Box<dyn Any + Send>; |
| assert!(e.is::<T>()); |
| let any = e.downcast::<T>().unwrap(); |
| assert!(any.is::<u16>()); |
| assert_eq!(*any.downcast::<u16>().unwrap(), 413); |
| } |
| Ok(()) => panic!() |
| } |
| } |
| |
| #[test] |
| fn test_try_panic_message_unit_struct() { |
| struct Juju; |
| |
| match thread::spawn(move|| { |
| panic!(Juju) |
| }).join() { |
| Err(ref e) if e.is::<Juju>() => {} |
| Err(_) | Ok(()) => panic!() |
| } |
| } |
| |
| #[test] |
| fn test_park_timeout_unpark_before() { |
| for _ in 0..10 { |
| thread::current().unpark(); |
| thread::park_timeout(Duration::from_millis(u32::MAX as u64)); |
| } |
| } |
| |
| #[test] |
| fn test_park_timeout_unpark_not_called() { |
| for _ in 0..10 { |
| thread::park_timeout(Duration::from_millis(10)); |
| } |
| } |
| |
| #[test] |
| fn test_park_timeout_unpark_called_other_thread() { |
| for _ in 0..10 { |
| let th = thread::current(); |
| |
| let _guard = thread::spawn(move || { |
| super::sleep(Duration::from_millis(50)); |
| th.unpark(); |
| }); |
| |
| thread::park_timeout(Duration::from_millis(u32::MAX as u64)); |
| } |
| } |
| |
| #[test] |
| fn sleep_ms_smoke() { |
| thread::sleep(Duration::from_millis(2)); |
| } |
| |
| #[test] |
| fn test_thread_id_equal() { |
| assert!(thread::current().id() == thread::current().id()); |
| } |
| |
| #[test] |
| fn test_thread_id_not_equal() { |
| let spawned_id = thread::spawn(|| thread::current().id()).join().unwrap(); |
| assert!(thread::current().id() != spawned_id); |
| } |
| |
| // NOTE: the corresponding test for stderr is in run-pass/thread-stderr, due |
| // to the test harness apparently interfering with stderr configuration. |
| } |