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//! 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::{Mutex, Condvar, Arc}; use crate::sync::atomic::AtomicUsize; use crate::sync::atomic::Ordering::SeqCst; use crate::sys::thread as imp; use crate::sys_common::mutex; use crate::sys_common::thread_info; use crate::sys_common::thread; 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::{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(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); #[cfg(feature = "backtrace")] let try_result = panic::catch_unwind(panic::AssertUnwindSafe(|| { crate::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 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. /// /// # 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`. /// /// 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 == crate::u64::MAX { panic!("failed to generate unique thread ID: bitspace exhausted"); } let id = COUNTER; COUNTER += 1; ThreadId(NonZeroU64::new(id).unwrap()) } } } //////////////////////////////////////////////////////////////////////////////// // 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 { 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. /// /// 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::sync::mpsc::{channel, Sender}; use crate::result; use crate::thread::{self, ThreadId}; use crate::time::Duration; use crate::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().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] #[cfg_attr(target_env = "sgx", ignore)] // FIXME: https://github.com/fortanix/rust-sgx/issues/31 fn test_park_timeout_unpark_not_called() { for _ in 0..10 { thread::park_timeout(Duration::from_millis(10)); } } #[test] #[cfg_attr(target_env = "sgx", ignore)] // FIXME: https://github.com/fortanix/rust-sgx/issues/31 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] #[cfg_attr(target_env = "sgx", ignore)] // FIXME: https://github.com/fortanix/rust-sgx/issues/31 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. }