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Diffstat (limited to 'src/libstd/thread/mod.rs')
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diff --git a/src/libstd/thread/mod.rs b/src/libstd/thread/mod.rs deleted file mode 100644 index 202867258f1..00000000000 --- a/src/libstd/thread/mod.rs +++ /dev/null @@ -1,1787 +0,0 @@ -//! 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 crate::any::Any; -use crate::cell::UnsafeCell; -use crate::ffi::{CStr, CString}; -use crate::fmt; -use crate::io; -use crate::mem; -use crate::num::NonZeroU64; -use crate::panic; -use crate::panicking; -use crate::str; -use crate::sync::atomic::AtomicUsize; -use crate::sync::atomic::Ordering::SeqCst; -use crate::sync::{Arc, Condvar, Mutex}; -use crate::sys::thread as imp; -use crate::sys_common::mutex; -use crate::sys_common::thread; -use crate::sys_common::thread_info; -use crate::sys_common::{AsInner, IntoInner}; -use crate::time::Duration; - -//////////////////////////////////////////////////////////////////////////////// -// Thread-local storage -//////////////////////////////////////////////////////////////////////////////// - -#[macro_use] -mod local; - -#[stable(feature = "rust1", since = "1.0.0")] -pub use self::local::{AccessError, LocalKey}; - -// 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 = "none")] -#[cfg(target_thread_local)] -#[doc(hidden)] -pub use self::local::fast::Key as __FastLocalKeyInner; -#[unstable(feature = "libstd_thread_internals", issue = "none")] -#[doc(hidden)] -pub use self::local::os::Key as __OsLocalKeyInner; -#[unstable(feature = "libstd_thread_internals", issue = "none")] -#[cfg(all(target_arch = "wasm32", not(target_feature = "atomics")))] -#[doc(hidden)] -pub use self::local::statik::Key as __StaticLocalKeyInner; - -//////////////////////////////////////////////////////////////////////////////// -// 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(32 * 1024); - /// - /// 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 - /// [`JoinHandle::join`]: ../../std/thread/struct.JoinHandle.html#method.join - #[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); - let try_result = panic::catch_unwind(panic::AssertUnwindSafe(|| { - crate::sys_common::backtrace::__rust_begin_short_backtrace(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 FnOnce() + 'a>, Box<dyn FnOnce() + '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).expect("failed to spawn thread") -} - -/// 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. -/// -/// This function is blocking, and should not be used in `async` functions. -/// -/// # 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. -/// -/// This function is blocking, and should not be used in `async` functions. -/// -/// # 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`. -/// -/// Notice that being unblocked does not imply any synchronization with someone -/// that unparked this thread, it could also be spurious. -/// For example, it would be a valid, but inefficient, implementation to make both [`park`] and -/// [`unpark`] return immediately without doing anything. -/// -/// 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 in a loop. 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::sync::{Arc, atomic::{Ordering, AtomicBool}}; -/// use std::time::Duration; -/// -/// let flag = Arc::new(AtomicBool::new(false)); -/// let flag2 = Arc::clone(&flag); -/// -/// let parked_thread = thread::spawn(move || { -/// // We want to wait until the flag is set. We *could* just spin, but using -/// // park/unpark is more efficient. -/// while !flag2.load(Ordering::Acquire) { -/// println!("Parking thread"); -/// thread::park(); -/// // We *could* get here spuriously, i.e., way before the 10ms below are over! -/// // But that is no problem, we are in a loop until the flag is set anyway. -/// println!("Thread unparked"); -/// } -/// println!("Flag received"); -/// }); -/// -/// // Let some time pass for the thread to be spawned. -/// thread::sleep(Duration::from_millis(10)); -/// -/// // Set the flag, and let the thread wake up. -/// // There is no race condition here, if `unpark` -/// // happens first, `park` will return immediately. -/// // Hence there is no risk of a deadlock. -/// flag.store(true, Ordering::Release); -/// 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(NonZeroU64); - -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 = 1; - - 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(NonZeroU64::new(id).unwrap()) - } - } - - /// This returns a numeric identifier for the thread identified by this - /// `ThreadId`. - /// - /// As noted in the documentation for the type itself, it is essentially an - /// opaque ID, but is guaranteed to be unique for each thread. The returned - /// value is entirely opaque -- only equality testing is stable. Note that - /// it is not guaranteed which values new threads will return, and this may - /// change across Rust versions. - #[unstable(feature = "thread_id_value", issue = "67939")] - pub fn as_u64(&self) -> NonZeroU64 { - self.0 - } -} - -//////////////////////////////////////////////////////////////////////////////// -// 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_deref() - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl fmt::Debug for Thread { - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - f.debug_struct("Thread").field("id", &self.id()).field("name", &self.name()).finish() - } -} - -//////////////////////////////////////////////////////////////////////////////// -// JoinHandle -//////////////////////////////////////////////////////////////////////////////// - -/// A specialized [`Result`] type for threads. -/// -/// Indicates the manner in which a thread exited. -/// -/// The value contained in the `Result::Err` variant -/// is the value the thread panicked with; -/// that is, the argument the `panic!` macro was called with. -/// Unlike with normal errors, this value doesn't implement -/// the [`Error`](crate::error::Error) trait. -/// -/// Thus, a sensible way to handle a thread panic is to either: -/// 1. `unwrap` the `Result<T>`, propagating the panic -/// 2. or in case the thread is intended to be a subsystem boundary -/// that is supposed to isolate system-level failures, -/// match on the `Err` variant and handle the panic in an appropriate way. -/// -/// 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> = crate::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 super::Builder; - use crate::any::Any; - use crate::mem; - use crate::result; - use crate::sync::mpsc::{channel, Sender}; - use crate::thread::{self, ThreadId}; - use crate::time::Duration; - - // !!! 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() - .expect("thread panicked"); - } - - #[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_size_of_option_thread_id() { - assert_eq!(mem::size_of::<Option<ThreadId>>(), mem::size_of::<ThreadId>()); - } - - #[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 ui/thread-stderr, due - // to the test harness apparently interfering with stderr configuration. -} |