3 //! ## The threading model
5 //! An executing Rust program consists of a collection of native OS threads,
6 //! each with their own stack and local state. Threads can be named, and
7 //! provide some built-in support for low-level synchronization.
9 //! Communication between threads can be done through
10 //! [channels], Rust's message-passing types, along with [other forms of thread
11 //! synchronization](../../std/sync/index.html) and shared-memory data
12 //! structures. In particular, types that are guaranteed to be
13 //! threadsafe are easily shared between threads using the
14 //! atomically-reference-counted container, [`Arc`].
16 //! Fatal logic errors in Rust cause *thread panic*, during which
17 //! a thread will unwind the stack, running destructors and freeing
18 //! owned resources. While not meant as a 'try/catch' mechanism, panics
19 //! in Rust can nonetheless be caught (unless compiling with `panic=abort`) with
20 //! [`catch_unwind`](../../std/panic/fn.catch_unwind.html) and recovered
21 //! from, or alternatively be resumed with
22 //! [`resume_unwind`](../../std/panic/fn.resume_unwind.html). If the panic
23 //! is not caught the thread will exit, but the panic may optionally be
24 //! detected from a different thread with [`join`]. If the main thread panics
25 //! without the panic being caught, the application will exit with a
26 //! non-zero exit code.
28 //! When the main thread of a Rust program terminates, the entire program shuts
29 //! down, even if other threads are still running. However, this module provides
30 //! convenient facilities for automatically waiting for the termination of a
31 //! child thread (i.e., join).
33 //! ## Spawning a thread
35 //! A new thread can be spawned using the [`thread::spawn`][`spawn`] function:
40 //! thread::spawn(move || {
45 //! In this example, the spawned thread is "detached" from the current
46 //! thread. This means that it can outlive its parent (the thread that spawned
47 //! it), unless this parent is the main thread.
49 //! The parent thread can also wait on the completion of the child
50 //! thread; a call to [`spawn`] produces a [`JoinHandle`], which provides
51 //! a `join` method for waiting:
56 //! let child = thread::spawn(move || {
60 //! let res = child.join();
63 //! The [`join`] method returns a [`thread::Result`] containing [`Ok`] of the final
64 //! value produced by the child thread, or [`Err`] of the value given to
65 //! a call to [`panic!`] if the child panicked.
67 //! ## Configuring threads
69 //! A new thread can be configured before it is spawned via the [`Builder`] type,
70 //! which currently allows you to set the name and stack size for the child thread:
73 //! # #![allow(unused_must_use)]
76 //! thread::Builder::new().name("child1".to_string()).spawn(move || {
77 //! println!("Hello, world!");
81 //! ## The `Thread` type
83 //! Threads are represented via the [`Thread`] type, which you can get in one of
86 //! * By spawning a new thread, e.g., using the [`thread::spawn`][`spawn`]
87 //! function, and calling [`thread`][`JoinHandle::thread`] on the [`JoinHandle`].
88 //! * By requesting the current thread, using the [`thread::current`] function.
90 //! The [`thread::current`] function is available even for threads not spawned
91 //! by the APIs of this module.
93 //! ## Thread-local storage
95 //! This module also provides an implementation of thread-local storage for Rust
96 //! programs. Thread-local storage is a method of storing data into a global
97 //! variable that each thread in the program will have its own copy of.
98 //! Threads do not share this data, so accesses do not need to be synchronized.
100 //! A thread-local key owns the value it contains and will destroy the value when the
101 //! thread exits. It is created with the [`thread_local!`] macro and can contain any
102 //! value that is `'static` (no borrowed pointers). It provides an accessor function,
103 //! [`with`], that yields a shared reference to the value to the specified
104 //! closure. Thread-local keys allow only shared access to values, as there would be no
105 //! way to guarantee uniqueness if mutable borrows were allowed. Most values
106 //! will want to make use of some form of **interior mutability** through the
107 //! [`Cell`] or [`RefCell`] types.
109 //! ## Naming threads
111 //! Threads are able to have associated names for identification purposes. By default, spawned
112 //! threads are unnamed. To specify a name for a thread, build the thread with [`Builder`] and pass
113 //! the desired thread name to [`Builder::name`]. To retrieve the thread name from within the
114 //! thread, use [`Thread::name`]. A couple examples of where the name of a thread gets used:
116 //! * If a panic occurs in a named thread, the thread name will be printed in the panic message.
117 //! * The thread name is provided to the OS where applicable (e.g., `pthread_setname_np` in
118 //! unix-like platforms).
122 //! The default stack size for spawned threads is 2 MiB, though this particular stack size is
123 //! subject to change in the future. There are two ways to manually specify the stack size for
126 //! * Build the thread with [`Builder`] and pass the desired stack size to [`Builder::stack_size`].
127 //! * Set the `RUST_MIN_STACK` environment variable to an integer representing the desired stack
128 //! size (in bytes). Note that setting [`Builder::stack_size`] will override this.
130 //! Note that the stack size of the main thread is *not* determined by Rust.
132 //! [channels]: ../../std/sync/mpsc/index.html
133 //! [`Arc`]: ../../std/sync/struct.Arc.html
134 //! [`spawn`]: ../../std/thread/fn.spawn.html
135 //! [`JoinHandle`]: ../../std/thread/struct.JoinHandle.html
136 //! [`JoinHandle::thread`]: ../../std/thread/struct.JoinHandle.html#method.thread
137 //! [`join`]: ../../std/thread/struct.JoinHandle.html#method.join
138 //! [`Result`]: ../../std/result/enum.Result.html
139 //! [`Ok`]: ../../std/result/enum.Result.html#variant.Ok
140 //! [`Err`]: ../../std/result/enum.Result.html#variant.Err
141 //! [`panic!`]: ../../std/macro.panic.html
142 //! [`Builder`]: ../../std/thread/struct.Builder.html
143 //! [`Builder::stack_size`]: ../../std/thread/struct.Builder.html#method.stack_size
144 //! [`Builder::name`]: ../../std/thread/struct.Builder.html#method.name
145 //! [`thread::current`]: ../../std/thread/fn.current.html
146 //! [`thread::Result`]: ../../std/thread/type.Result.html
147 //! [`Thread`]: ../../std/thread/struct.Thread.html
148 //! [`park`]: ../../std/thread/fn.park.html
149 //! [`unpark`]: ../../std/thread/struct.Thread.html#method.unpark
150 //! [`Thread::name`]: ../../std/thread/struct.Thread.html#method.name
151 //! [`thread::park_timeout`]: ../../std/thread/fn.park_timeout.html
152 //! [`Cell`]: ../cell/struct.Cell.html
153 //! [`RefCell`]: ../cell/struct.RefCell.html
154 //! [`thread_local!`]: ../macro.thread_local.html
155 //! [`with`]: struct.LocalKey.html#method.with
157 #![stable(feature = "rust1", since = "1.0.0")]
160 use crate::cell::UnsafeCell;
161 use crate::ffi::{CStr, CString};
165 use crate::num::NonZeroU64;
167 use crate::panicking;
169 use crate::sync::atomic::AtomicUsize;
170 use crate::sync::atomic::Ordering::SeqCst;
171 use crate::sync::{Arc, Condvar, Mutex};
172 use crate::sys::thread as imp;
173 use crate::sys_common::mutex;
174 use crate::sys_common::thread;
175 use crate::sys_common::thread_info;
176 use crate::sys_common::{AsInner, IntoInner};
177 use crate::time::Duration;
179 ////////////////////////////////////////////////////////////////////////////////
180 // Thread-local storage
181 ////////////////////////////////////////////////////////////////////////////////
186 #[stable(feature = "rust1", since = "1.0.0")]
187 pub use self::local::{AccessError, LocalKey};
189 // The types used by the thread_local! macro to access TLS keys. Note that there
190 // are two types, the "OS" type and the "fast" type. The OS thread local key
191 // type is accessed via platform-specific API calls and is slow, while the fast
192 // key type is accessed via code generated via LLVM, where TLS keys are set up
193 // by the elf linker. Note that the OS TLS type is always available: on macOS
194 // the standard library is compiled with support for older platform versions
195 // where fast TLS was not available; end-user code is compiled with fast TLS
196 // where available, but both are needed.
198 #[unstable(feature = "libstd_thread_internals", issue = "none")]
199 #[cfg(target_thread_local)]
201 pub use self::local::fast::Key as __FastLocalKeyInner;
202 #[unstable(feature = "libstd_thread_internals", issue = "none")]
204 pub use self::local::os::Key as __OsLocalKeyInner;
205 #[unstable(feature = "libstd_thread_internals", issue = "none")]
206 #[cfg(all(target_arch = "wasm32", not(target_feature = "atomics")))]
208 pub use self::local::statik::Key as __StaticLocalKeyInner;
210 ////////////////////////////////////////////////////////////////////////////////
212 ////////////////////////////////////////////////////////////////////////////////
214 /// Thread factory, which can be used in order to configure the properties of
217 /// Methods can be chained on it in order to configure it.
219 /// The two configurations available are:
221 /// - [`name`]: specifies an [associated name for the thread][naming-threads]
222 /// - [`stack_size`]: specifies the [desired stack size for the thread][stack-size]
224 /// The [`spawn`] method will take ownership of the builder and create an
225 /// [`io::Result`] to the thread handle with the given configuration.
227 /// The [`thread::spawn`] free function uses a `Builder` with default
228 /// configuration and [`unwrap`]s its return value.
230 /// You may want to use [`spawn`] instead of [`thread::spawn`], when you want
231 /// to recover from a failure to launch a thread, indeed the free function will
232 /// panic where the `Builder` method will return a [`io::Result`].
239 /// let builder = thread::Builder::new();
241 /// let handler = builder.spawn(|| {
245 /// handler.join().unwrap();
248 /// [`thread::spawn`]: ../../std/thread/fn.spawn.html
249 /// [`stack_size`]: ../../std/thread/struct.Builder.html#method.stack_size
250 /// [`name`]: ../../std/thread/struct.Builder.html#method.name
251 /// [`spawn`]: ../../std/thread/struct.Builder.html#method.spawn
252 /// [`io::Result`]: ../../std/io/type.Result.html
253 /// [`unwrap`]: ../../std/result/enum.Result.html#method.unwrap
254 /// [naming-threads]: ./index.html#naming-threads
255 /// [stack-size]: ./index.html#stack-size
256 #[stable(feature = "rust1", since = "1.0.0")]
259 // A name for the thread-to-be, for identification in panic messages
260 name: Option<String>,
261 // The size of the stack for the spawned thread in bytes
262 stack_size: Option<usize>,
266 /// Generates the base configuration for spawning a thread, from which
267 /// configuration methods can be chained.
274 /// let builder = thread::Builder::new()
275 /// .name("foo".into())
276 /// .stack_size(32 * 1024);
278 /// let handler = builder.spawn(|| {
282 /// handler.join().unwrap();
284 #[stable(feature = "rust1", since = "1.0.0")]
285 pub fn new() -> Builder {
286 Builder { name: None, stack_size: None }
289 /// Names the thread-to-be. Currently the name is used for identification
290 /// only in panic messages.
292 /// The name must not contain null bytes (`\0`).
294 /// For more information about named threads, see
295 /// [this module-level documentation][naming-threads].
302 /// let builder = thread::Builder::new()
303 /// .name("foo".into());
305 /// let handler = builder.spawn(|| {
306 /// assert_eq!(thread::current().name(), Some("foo"))
309 /// handler.join().unwrap();
312 /// [naming-threads]: ./index.html#naming-threads
313 #[stable(feature = "rust1", since = "1.0.0")]
314 pub fn name(mut self, name: String) -> Builder {
315 self.name = Some(name);
319 /// Sets the size of the stack (in bytes) for the new thread.
321 /// The actual stack size may be greater than this value if
322 /// the platform specifies a minimal stack size.
324 /// For more information about the stack size for threads, see
325 /// [this module-level documentation][stack-size].
332 /// let builder = thread::Builder::new().stack_size(32 * 1024);
335 /// [stack-size]: ./index.html#stack-size
336 #[stable(feature = "rust1", since = "1.0.0")]
337 pub fn stack_size(mut self, size: usize) -> Builder {
338 self.stack_size = Some(size);
342 /// Spawns a new thread by taking ownership of the `Builder`, and returns an
343 /// [`io::Result`] to its [`JoinHandle`].
345 /// The spawned thread may outlive the caller (unless the caller thread
346 /// is the main thread; the whole process is terminated when the main
347 /// thread finishes). The join handle can be used to block on
348 /// termination of the child thread, including recovering its panics.
350 /// For a more complete documentation see [`thread::spawn`][`spawn`].
354 /// Unlike the [`spawn`] free function, this method yields an
355 /// [`io::Result`] to capture any failure to create the thread at
358 /// [`spawn`]: ../../std/thread/fn.spawn.html
359 /// [`io::Result`]: ../../std/io/type.Result.html
360 /// [`JoinHandle`]: ../../std/thread/struct.JoinHandle.html
364 /// Panics if a thread name was set and it contained null bytes.
371 /// let builder = thread::Builder::new();
373 /// let handler = builder.spawn(|| {
377 /// handler.join().unwrap();
379 #[stable(feature = "rust1", since = "1.0.0")]
380 pub fn spawn<F, T>(self, f: F) -> io::Result<JoinHandle<T>>
386 unsafe { self.spawn_unchecked(f) }
389 /// Spawns a new thread without any lifetime restrictions by taking ownership
390 /// of the `Builder`, and returns an [`io::Result`] to its [`JoinHandle`].
392 /// The spawned thread may outlive the caller (unless the caller thread
393 /// is the main thread; the whole process is terminated when the main
394 /// thread finishes). The join handle can be used to block on
395 /// termination of the child thread, including recovering its panics.
397 /// This method is identical to [`thread::Builder::spawn`][`Builder::spawn`],
398 /// except for the relaxed lifetime bounds, which render it unsafe.
399 /// For a more complete documentation see [`thread::spawn`][`spawn`].
403 /// Unlike the [`spawn`] free function, this method yields an
404 /// [`io::Result`] to capture any failure to create the thread at
409 /// Panics if a thread name was set and it contained null bytes.
413 /// The caller has to ensure that no references in the supplied thread closure
414 /// or its return type can outlive the spawned thread's lifetime. This can be
415 /// guaranteed in two ways:
417 /// - ensure that [`join`][`JoinHandle::join`] is called before any referenced
419 /// - use only types with `'static` lifetime bounds, i.e., those with no or only
420 /// `'static` references (both [`thread::Builder::spawn`][`Builder::spawn`]
421 /// and [`thread::spawn`][`spawn`] enforce this property statically)
426 /// #![feature(thread_spawn_unchecked)]
429 /// let builder = thread::Builder::new();
432 /// let thread_x = &x;
434 /// let handler = unsafe {
435 /// builder.spawn_unchecked(move || {
436 /// println!("x = {}", *thread_x);
440 /// // caller has to ensure `join()` is called, otherwise
441 /// // it is possible to access freed memory if `x` gets
442 /// // dropped before the thread closure is executed!
443 /// handler.join().unwrap();
446 /// [`spawn`]: ../../std/thread/fn.spawn.html
447 /// [`Builder::spawn`]: ../../std/thread/struct.Builder.html#method.spawn
448 /// [`io::Result`]: ../../std/io/type.Result.html
449 /// [`JoinHandle`]: ../../std/thread/struct.JoinHandle.html
450 /// [`JoinHandle::join`]: ../../std/thread/struct.JoinHandle.html#method.join
451 #[unstable(feature = "thread_spawn_unchecked", issue = "55132")]
452 pub unsafe fn spawn_unchecked<'a, F, T>(self, f: F) -> io::Result<JoinHandle<T>>
458 let Builder { name, stack_size } = self;
460 let stack_size = stack_size.unwrap_or_else(thread::min_stack);
462 let my_thread = Thread::new(name);
463 let their_thread = my_thread.clone();
465 let my_packet: Arc<UnsafeCell<Option<Result<T>>>> = Arc::new(UnsafeCell::new(None));
466 let their_packet = my_packet.clone();
469 if let Some(name) = their_thread.cname() {
470 imp::Thread::set_name(name);
473 thread_info::set(imp::guard::current(), their_thread);
474 let try_result = panic::catch_unwind(panic::AssertUnwindSafe(|| {
475 crate::sys_common::backtrace::__rust_begin_short_backtrace(f)
477 *their_packet.get() = Some(try_result);
480 Ok(JoinHandle(JoinInner {
481 // `imp::Thread::new` takes a closure with a `'static` lifetime, since it's passed
482 // through FFI or otherwise used with low-level threading primitives that have no
483 // notion of or way to enforce lifetimes.
485 // As mentioned in the `Safety` section of this function's documentation, the caller of
486 // this function needs to guarantee that the passed-in lifetime is sufficiently long
487 // for the lifetime of the thread.
489 // Similarly, the `sys` implementation must guarantee that no references to the closure
490 // exist after the thread has terminated, which is signaled by `Thread::join`
492 native: Some(imp::Thread::new(
494 mem::transmute::<Box<dyn FnOnce() + 'a>, Box<dyn FnOnce() + 'static>>(Box::new(
499 packet: Packet(my_packet),
504 ////////////////////////////////////////////////////////////////////////////////
506 ////////////////////////////////////////////////////////////////////////////////
508 /// Spawns a new thread, returning a [`JoinHandle`] for it.
510 /// The join handle will implicitly *detach* the child thread upon being
511 /// dropped. In this case, the child thread may outlive the parent (unless
512 /// the parent thread is the main thread; the whole process is terminated when
513 /// the main thread finishes). Additionally, the join handle provides a [`join`]
514 /// method that can be used to join the child thread. If the child thread
515 /// panics, [`join`] will return an [`Err`] containing the argument given to
518 /// This will create a thread using default parameters of [`Builder`], if you
519 /// want to specify the stack size or the name of the thread, use this API
522 /// As you can see in the signature of `spawn` there are two constraints on
523 /// both the closure given to `spawn` and its return value, let's explain them:
525 /// - The `'static` constraint means that the closure and its return value
526 /// must have a lifetime of the whole program execution. The reason for this
527 /// is that threads can `detach` and outlive the lifetime they have been
529 /// Indeed if the thread, and by extension its return value, can outlive their
530 /// caller, we need to make sure that they will be valid afterwards, and since
531 /// we *can't* know when it will return we need to have them valid as long as
532 /// possible, that is until the end of the program, hence the `'static`
534 /// - The [`Send`] constraint is because the closure will need to be passed
535 /// *by value* from the thread where it is spawned to the new thread. Its
536 /// return value will need to be passed from the new thread to the thread
537 /// where it is `join`ed.
538 /// As a reminder, the [`Send`] marker trait expresses that it is safe to be
539 /// passed from thread to thread. [`Sync`] expresses that it is safe to have a
540 /// reference be passed from thread to thread.
544 /// Panics if the OS fails to create a thread; use [`Builder::spawn`]
545 /// to recover from such errors.
549 /// Creating a thread.
554 /// let handler = thread::spawn(|| {
558 /// handler.join().unwrap();
561 /// As mentioned in the module documentation, threads are usually made to
562 /// communicate using [`channels`], here is how it usually looks.
564 /// This example also shows how to use `move`, in order to give ownership
565 /// of values to a thread.
569 /// use std::sync::mpsc::channel;
571 /// let (tx, rx) = channel();
573 /// let sender = thread::spawn(move || {
574 /// tx.send("Hello, thread".to_owned())
575 /// .expect("Unable to send on channel");
578 /// let receiver = thread::spawn(move || {
579 /// let value = rx.recv().expect("Unable to receive from channel");
580 /// println!("{}", value);
583 /// sender.join().expect("The sender thread has panicked");
584 /// receiver.join().expect("The receiver thread has panicked");
587 /// A thread can also return a value through its [`JoinHandle`], you can use
588 /// this to make asynchronous computations (futures might be more appropriate
594 /// let computation = thread::spawn(|| {
595 /// // Some expensive computation.
599 /// let result = computation.join().unwrap();
600 /// println!("{}", result);
603 /// [`channels`]: ../../std/sync/mpsc/index.html
604 /// [`JoinHandle`]: ../../std/thread/struct.JoinHandle.html
605 /// [`join`]: ../../std/thread/struct.JoinHandle.html#method.join
606 /// [`Err`]: ../../std/result/enum.Result.html#variant.Err
607 /// [`panic`]: ../../std/macro.panic.html
608 /// [`Builder::spawn`]: ../../std/thread/struct.Builder.html#method.spawn
609 /// [`Builder`]: ../../std/thread/struct.Builder.html
610 /// [`Send`]: ../../std/marker/trait.Send.html
611 /// [`Sync`]: ../../std/marker/trait.Sync.html
612 #[stable(feature = "rust1", since = "1.0.0")]
613 pub fn spawn<F, T>(f: F) -> JoinHandle<T>
619 Builder::new().spawn(f).expect("failed to spawn thread")
622 /// Gets a handle to the thread that invokes it.
626 /// Getting a handle to the current thread with `thread::current()`:
631 /// let handler = thread::Builder::new()
632 /// .name("named thread".into())
634 /// let handle = thread::current();
635 /// assert_eq!(handle.name(), Some("named thread"));
639 /// handler.join().unwrap();
641 #[stable(feature = "rust1", since = "1.0.0")]
642 pub fn current() -> Thread {
643 thread_info::current_thread().expect(
644 "use of std::thread::current() is not possible \
645 after the thread's local data has been destroyed",
649 /// Cooperatively gives up a timeslice to the OS scheduler.
651 /// This is used when the programmer knows that the thread will have nothing
652 /// to do for some time, and thus avoid wasting computing time.
654 /// For example when polling on a resource, it is common to check that it is
655 /// available, and if not to yield in order to avoid busy waiting.
657 /// Thus the pattern of `yield`ing after a failed poll is rather common when
658 /// implementing low-level shared resources or synchronization primitives.
660 /// However programmers will usually prefer to use [`channel`]s, [`Condvar`]s,
661 /// [`Mutex`]es or [`join`] for their synchronization routines, as they avoid
662 /// thinking about thread scheduling.
664 /// Note that [`channel`]s for example are implemented using this primitive.
665 /// Indeed when you call `send` or `recv`, which are blocking, they will yield
666 /// if the channel is not available.
673 /// thread::yield_now();
676 /// [`channel`]: ../../std/sync/mpsc/index.html
677 /// [`spawn`]: ../../std/thread/fn.spawn.html
678 /// [`join`]: ../../std/thread/struct.JoinHandle.html#method.join
679 /// [`Mutex`]: ../../std/sync/struct.Mutex.html
680 /// [`Condvar`]: ../../std/sync/struct.Condvar.html
681 #[stable(feature = "rust1", since = "1.0.0")]
683 imp::Thread::yield_now()
686 /// Determines whether the current thread is unwinding because of panic.
688 /// A common use of this feature is to poison shared resources when writing
689 /// unsafe code, by checking `panicking` when the `drop` is called.
691 /// This is usually not needed when writing safe code, as [`Mutex`es][Mutex]
692 /// already poison themselves when a thread panics while holding the lock.
694 /// This can also be used in multithreaded applications, in order to send a
695 /// message to other threads warning that a thread has panicked (e.g., for
696 /// monitoring purposes).
703 /// struct SomeStruct;
705 /// impl Drop for SomeStruct {
706 /// fn drop(&mut self) {
707 /// if thread::panicking() {
708 /// println!("dropped while unwinding");
710 /// println!("dropped while not unwinding");
717 /// let a = SomeStruct;
722 /// let b = SomeStruct;
727 /// [Mutex]: ../../std/sync/struct.Mutex.html
729 #[stable(feature = "rust1", since = "1.0.0")]
730 pub fn panicking() -> bool {
731 panicking::panicking()
734 /// Puts the current thread to sleep for at least the specified amount of time.
736 /// The thread may sleep longer than the duration specified due to scheduling
737 /// specifics or platform-dependent functionality. It will never sleep less.
739 /// This function is blocking, and should not be used in `async` functions.
741 /// # Platform-specific behavior
743 /// On Unix platforms, the underlying syscall may be interrupted by a
744 /// spurious wakeup or signal handler. To ensure the sleep occurs for at least
745 /// the specified duration, this function may invoke that system call multiple
753 /// // Let's sleep for 2 seconds:
754 /// thread::sleep_ms(2000);
756 #[stable(feature = "rust1", since = "1.0.0")]
757 #[rustc_deprecated(since = "1.6.0", reason = "replaced by `std::thread::sleep`")]
758 pub fn sleep_ms(ms: u32) {
759 sleep(Duration::from_millis(ms as u64))
762 /// Puts the current thread to sleep for at least the specified amount of time.
764 /// The thread may sleep longer than the duration specified due to scheduling
765 /// specifics or platform-dependent functionality. It will never sleep less.
767 /// This function is blocking, and should not be used in `async` functions.
769 /// # Platform-specific behavior
771 /// On Unix platforms, the underlying syscall may be interrupted by a
772 /// spurious wakeup or signal handler. To ensure the sleep occurs for at least
773 /// the specified duration, this function may invoke that system call multiple
775 /// Platforms which do not support nanosecond precision for sleeping will
776 /// have `dur` rounded up to the nearest granularity of time they can sleep for.
781 /// use std::{thread, time};
783 /// let ten_millis = time::Duration::from_millis(10);
784 /// let now = time::Instant::now();
786 /// thread::sleep(ten_millis);
788 /// assert!(now.elapsed() >= ten_millis);
790 #[stable(feature = "thread_sleep", since = "1.4.0")]
791 pub fn sleep(dur: Duration) {
792 imp::Thread::sleep(dur)
795 // constants for park/unpark
796 const EMPTY: usize = 0;
797 const PARKED: usize = 1;
798 const NOTIFIED: usize = 2;
800 /// Blocks unless or until the current thread's token is made available.
802 /// A call to `park` does not guarantee that the thread will remain parked
803 /// forever, and callers should be prepared for this possibility.
805 /// # park and unpark
807 /// Every thread is equipped with some basic low-level blocking support, via the
808 /// [`thread::park`][`park`] function and [`thread::Thread::unpark`][`unpark`]
809 /// method. [`park`] blocks the current thread, which can then be resumed from
810 /// another thread by calling the [`unpark`] method on the blocked thread's
813 /// Conceptually, each [`Thread`] handle has an associated token, which is
814 /// initially not present:
816 /// * The [`thread::park`][`park`] function blocks the current thread unless or
817 /// until the token is available for its thread handle, at which point it
818 /// atomically consumes the token. It may also return *spuriously*, without
819 /// consuming the token. [`thread::park_timeout`] does the same, but allows
820 /// specifying a maximum time to block the thread for.
822 /// * The [`unpark`] method on a [`Thread`] atomically makes the token available
823 /// if it wasn't already. Because the token is initially absent, [`unpark`]
824 /// followed by [`park`] will result in the second call returning immediately.
826 /// In other words, each [`Thread`] acts a bit like a spinlock that can be
827 /// locked and unlocked using `park` and `unpark`.
829 /// Notice that being unblocked does not imply any synchronization with someone
830 /// that unparked this thread, it could also be spurious.
831 /// For example, it would be a valid, but inefficient, implementation to make both [`park`] and
832 /// [`unpark`] return immediately without doing anything.
834 /// The API is typically used by acquiring a handle to the current thread,
835 /// placing that handle in a shared data structure so that other threads can
836 /// find it, and then `park`ing in a loop. When some desired condition is met, another
837 /// thread calls [`unpark`] on the handle.
839 /// The motivation for this design is twofold:
841 /// * It avoids the need to allocate mutexes and condvars when building new
842 /// synchronization primitives; the threads already provide basic
843 /// blocking/signaling.
845 /// * It can be implemented very efficiently on many platforms.
851 /// use std::sync::{Arc, atomic::{Ordering, AtomicBool}};
852 /// use std::time::Duration;
854 /// let flag = Arc::new(AtomicBool::new(false));
855 /// let flag2 = Arc::clone(&flag);
857 /// let parked_thread = thread::spawn(move || {
858 /// // We want to wait until the flag is set. We *could* just spin, but using
859 /// // park/unpark is more efficient.
860 /// while !flag2.load(Ordering::Acquire) {
861 /// println!("Parking thread");
863 /// // We *could* get here spuriously, i.e., way before the 10ms below are over!
864 /// // But that is no problem, we are in a loop until the flag is set anyway.
865 /// println!("Thread unparked");
867 /// println!("Flag received");
870 /// // Let some time pass for the thread to be spawned.
871 /// thread::sleep(Duration::from_millis(10));
873 /// // Set the flag, and let the thread wake up.
874 /// // There is no race condition here, if `unpark`
875 /// // happens first, `park` will return immediately.
876 /// // Hence there is no risk of a deadlock.
877 /// flag.store(true, Ordering::Release);
878 /// println!("Unpark the thread");
879 /// parked_thread.thread().unpark();
881 /// parked_thread.join().unwrap();
884 /// [`Thread`]: ../../std/thread/struct.Thread.html
885 /// [`park`]: ../../std/thread/fn.park.html
886 /// [`unpark`]: ../../std/thread/struct.Thread.html#method.unpark
887 /// [`thread::park_timeout`]: ../../std/thread/fn.park_timeout.html
889 // The implementation currently uses the trivial strategy of a Mutex+Condvar
890 // with wakeup flag, which does not actually allow spurious wakeups. In the
891 // future, this will be implemented in a more efficient way, perhaps along the lines of
892 // http://cr.openjdk.java.net/~stefank/6989984.1/raw_files/new/src/os/linux/vm/os_linux.cpp
893 // or futuxes, and in either case may allow spurious wakeups.
894 #[stable(feature = "rust1", since = "1.0.0")]
896 let thread = current();
898 // If we were previously notified then we consume this notification and
900 if thread.inner.state.compare_exchange(NOTIFIED, EMPTY, SeqCst, SeqCst).is_ok() {
904 // Otherwise we need to coordinate going to sleep
905 let mut m = thread.inner.lock.lock().unwrap();
906 match thread.inner.state.compare_exchange(EMPTY, PARKED, SeqCst, SeqCst) {
909 // We must read here, even though we know it will be `NOTIFIED`.
910 // This is because `unpark` may have been called again since we read
911 // `NOTIFIED` in the `compare_exchange` above. We must perform an
912 // acquire operation that synchronizes with that `unpark` to observe
913 // any writes it made before the call to unpark. To do that we must
914 // read from the write it made to `state`.
915 let old = thread.inner.state.swap(EMPTY, SeqCst);
916 assert_eq!(old, NOTIFIED, "park state changed unexpectedly");
918 } // should consume this notification, so prohibit spurious wakeups in next park.
919 Err(_) => panic!("inconsistent park state"),
922 m = thread.inner.cvar.wait(m).unwrap();
923 match thread.inner.state.compare_exchange(NOTIFIED, EMPTY, SeqCst, SeqCst) {
924 Ok(_) => return, // got a notification
925 Err(_) => {} // spurious wakeup, go back to sleep
930 /// Use [`park_timeout`].
932 /// Blocks unless or until the current thread's token is made available or
933 /// the specified duration has been reached (may wake spuriously).
935 /// The semantics of this function are equivalent to [`park`] except
936 /// that the thread will be blocked for roughly no longer than `dur`. This
937 /// method should not be used for precise timing due to anomalies such as
938 /// preemption or platform differences that may not cause the maximum
939 /// amount of time waited to be precisely `ms` long.
941 /// See the [park documentation][`park`] for more detail.
943 /// [`park_timeout`]: fn.park_timeout.html
944 /// [`park`]: ../../std/thread/fn.park.html
945 #[stable(feature = "rust1", since = "1.0.0")]
946 #[rustc_deprecated(since = "1.6.0", reason = "replaced by `std::thread::park_timeout`")]
947 pub fn park_timeout_ms(ms: u32) {
948 park_timeout(Duration::from_millis(ms as u64))
951 /// Blocks unless or until the current thread's token is made available or
952 /// the specified duration has been reached (may wake spuriously).
954 /// The semantics of this function are equivalent to [`park`][park] except
955 /// that the thread will be blocked for roughly no longer than `dur`. This
956 /// method should not be used for precise timing due to anomalies such as
957 /// preemption or platform differences that may not cause the maximum
958 /// amount of time waited to be precisely `dur` long.
960 /// See the [park documentation][park] for more details.
962 /// # Platform-specific behavior
964 /// Platforms which do not support nanosecond precision for sleeping will have
965 /// `dur` rounded up to the nearest granularity of time they can sleep for.
969 /// Waiting for the complete expiration of the timeout:
972 /// use std::thread::park_timeout;
973 /// use std::time::{Instant, Duration};
975 /// let timeout = Duration::from_secs(2);
976 /// let beginning_park = Instant::now();
978 /// let mut timeout_remaining = timeout;
980 /// park_timeout(timeout_remaining);
981 /// let elapsed = beginning_park.elapsed();
982 /// if elapsed >= timeout {
985 /// println!("restarting park_timeout after {:?}", elapsed);
986 /// timeout_remaining = timeout - elapsed;
990 /// [park]: fn.park.html
991 #[stable(feature = "park_timeout", since = "1.4.0")]
992 pub fn park_timeout(dur: Duration) {
993 let thread = current();
995 // Like `park` above we have a fast path for an already-notified thread, and
996 // afterwards we start coordinating for a sleep.
998 if thread.inner.state.compare_exchange(NOTIFIED, EMPTY, SeqCst, SeqCst).is_ok() {
1001 let m = thread.inner.lock.lock().unwrap();
1002 match thread.inner.state.compare_exchange(EMPTY, PARKED, SeqCst, SeqCst) {
1005 // We must read again here, see `park`.
1006 let old = thread.inner.state.swap(EMPTY, SeqCst);
1007 assert_eq!(old, NOTIFIED, "park state changed unexpectedly");
1009 } // should consume this notification, so prohibit spurious wakeups in next park.
1010 Err(_) => panic!("inconsistent park_timeout state"),
1013 // Wait with a timeout, and if we spuriously wake up or otherwise wake up
1014 // from a notification we just want to unconditionally set the state back to
1015 // empty, either consuming a notification or un-flagging ourselves as
1017 let (_m, _result) = thread.inner.cvar.wait_timeout(m, dur).unwrap();
1018 match thread.inner.state.swap(EMPTY, SeqCst) {
1019 NOTIFIED => {} // got a notification, hurray!
1020 PARKED => {} // no notification, alas
1021 n => panic!("inconsistent park_timeout state: {}", n),
1025 ////////////////////////////////////////////////////////////////////////////////
1027 ////////////////////////////////////////////////////////////////////////////////
1029 /// A unique identifier for a running thread.
1031 /// A `ThreadId` is an opaque object that has a unique value for each thread
1032 /// that creates one. `ThreadId`s are not guaranteed to correspond to a thread's
1033 /// system-designated identifier. A `ThreadId` can be retrieved from the [`id`]
1034 /// method on a [`Thread`].
1039 /// use std::thread;
1041 /// let other_thread = thread::spawn(|| {
1042 /// thread::current().id()
1045 /// let other_thread_id = other_thread.join().unwrap();
1046 /// assert!(thread::current().id() != other_thread_id);
1049 /// [`id`]: ../../std/thread/struct.Thread.html#method.id
1050 /// [`Thread`]: ../../std/thread/struct.Thread.html
1051 #[stable(feature = "thread_id", since = "1.19.0")]
1052 #[derive(Eq, PartialEq, Clone, Copy, Hash, Debug)]
1053 pub struct ThreadId(NonZeroU64);
1056 // Generate a new unique thread ID.
1057 fn new() -> ThreadId {
1058 // We never call `GUARD.init()`, so it is UB to attempt to
1059 // acquire this mutex reentrantly!
1060 static GUARD: mutex::Mutex = mutex::Mutex::new();
1061 static mut COUNTER: u64 = 1;
1064 let _guard = GUARD.lock();
1066 // If we somehow use up all our bits, panic so that we're not
1067 // covering up subtle bugs of IDs being reused.
1068 if COUNTER == u64::MAX {
1069 panic!("failed to generate unique thread ID: bitspace exhausted");
1075 ThreadId(NonZeroU64::new(id).unwrap())
1079 /// This returns a numeric identifier for the thread identified by this
1082 /// As noted in the documentation for the type itself, it is essentially an
1083 /// opaque ID, but is guaranteed to be unique for each thread. The returned
1084 /// value is entirely opaque -- only equality testing is stable. Note that
1085 /// it is not guaranteed which values new threads will return, and this may
1086 /// change across Rust versions.
1087 #[unstable(feature = "thread_id_value", issue = "67939")]
1088 pub fn as_u64(&self) -> NonZeroU64 {
1093 ////////////////////////////////////////////////////////////////////////////////
1095 ////////////////////////////////////////////////////////////////////////////////
1097 /// The internal representation of a `Thread` handle
1099 name: Option<CString>, // Guaranteed to be UTF-8
1102 // state for thread park/unpark
1109 #[stable(feature = "rust1", since = "1.0.0")]
1110 /// A handle to a thread.
1112 /// Threads are represented via the `Thread` type, which you can get in one of
1115 /// * By spawning a new thread, e.g., using the [`thread::spawn`][`spawn`]
1116 /// function, and calling [`thread`][`JoinHandle::thread`] on the
1118 /// * By requesting the current thread, using the [`thread::current`] function.
1120 /// The [`thread::current`] function is available even for threads not spawned
1121 /// by the APIs of this module.
1123 /// There is usually no need to create a `Thread` struct yourself, one
1124 /// should instead use a function like `spawn` to create new threads, see the
1125 /// docs of [`Builder`] and [`spawn`] for more details.
1127 /// [`Builder`]: ../../std/thread/struct.Builder.html
1128 /// [`JoinHandle::thread`]: ../../std/thread/struct.JoinHandle.html#method.thread
1129 /// [`JoinHandle`]: ../../std/thread/struct.JoinHandle.html
1130 /// [`thread::current`]: ../../std/thread/fn.current.html
1131 /// [`spawn`]: ../../std/thread/fn.spawn.html
1138 // Used only internally to construct a thread object without spawning
1139 // Panics if the name contains nuls.
1140 pub(crate) fn new(name: Option<String>) -> Thread {
1142 name.map(|n| CString::new(n).expect("thread name may not contain interior null bytes"));
1144 inner: Arc::new(Inner {
1146 id: ThreadId::new(),
1147 state: AtomicUsize::new(EMPTY),
1148 lock: Mutex::new(()),
1149 cvar: Condvar::new(),
1154 /// Atomically makes the handle's token available if it is not already.
1156 /// Every thread is equipped with some basic low-level blocking support, via
1157 /// the [`park`][park] function and the `unpark()` method. These can be
1158 /// used as a more CPU-efficient implementation of a spinlock.
1160 /// See the [park documentation][park] for more details.
1165 /// use std::thread;
1166 /// use std::time::Duration;
1168 /// let parked_thread = thread::Builder::new()
1170 /// println!("Parking thread");
1172 /// println!("Thread unparked");
1176 /// // Let some time pass for the thread to be spawned.
1177 /// thread::sleep(Duration::from_millis(10));
1179 /// println!("Unpark the thread");
1180 /// parked_thread.thread().unpark();
1182 /// parked_thread.join().unwrap();
1185 /// [park]: fn.park.html
1186 #[stable(feature = "rust1", since = "1.0.0")]
1187 pub fn unpark(&self) {
1188 // To ensure the unparked thread will observe any writes we made
1189 // before this call, we must perform a release operation that `park`
1190 // can synchronize with. To do that we must write `NOTIFIED` even if
1191 // `state` is already `NOTIFIED`. That is why this must be a swap
1192 // rather than a compare-and-swap that returns if it reads `NOTIFIED`
1194 match self.inner.state.swap(NOTIFIED, SeqCst) {
1195 EMPTY => return, // no one was waiting
1196 NOTIFIED => return, // already unparked
1197 PARKED => {} // gotta go wake someone up
1198 _ => panic!("inconsistent state in unpark"),
1201 // There is a period between when the parked thread sets `state` to
1202 // `PARKED` (or last checked `state` in the case of a spurious wake
1203 // up) and when it actually waits on `cvar`. If we were to notify
1204 // during this period it would be ignored and then when the parked
1205 // thread went to sleep it would never wake up. Fortunately, it has
1206 // `lock` locked at this stage so we can acquire `lock` to wait until
1207 // it is ready to receive the notification.
1209 // Releasing `lock` before the call to `notify_one` means that when the
1210 // parked thread wakes it doesn't get woken only to have to wait for us
1211 // to release `lock`.
1212 drop(self.inner.lock.lock().unwrap());
1213 self.inner.cvar.notify_one()
1216 /// Gets the thread's unique identifier.
1221 /// use std::thread;
1223 /// let other_thread = thread::spawn(|| {
1224 /// thread::current().id()
1227 /// let other_thread_id = other_thread.join().unwrap();
1228 /// assert!(thread::current().id() != other_thread_id);
1230 #[stable(feature = "thread_id", since = "1.19.0")]
1231 pub fn id(&self) -> ThreadId {
1235 /// Gets the thread's name.
1237 /// For more information about named threads, see
1238 /// [this module-level documentation][naming-threads].
1242 /// Threads by default have no name specified:
1245 /// use std::thread;
1247 /// let builder = thread::Builder::new();
1249 /// let handler = builder.spawn(|| {
1250 /// assert!(thread::current().name().is_none());
1253 /// handler.join().unwrap();
1256 /// Thread with a specified name:
1259 /// use std::thread;
1261 /// let builder = thread::Builder::new()
1262 /// .name("foo".into());
1264 /// let handler = builder.spawn(|| {
1265 /// assert_eq!(thread::current().name(), Some("foo"))
1268 /// handler.join().unwrap();
1271 /// [naming-threads]: ./index.html#naming-threads
1272 #[stable(feature = "rust1", since = "1.0.0")]
1273 pub fn name(&self) -> Option<&str> {
1274 self.cname().map(|s| unsafe { str::from_utf8_unchecked(s.to_bytes()) })
1277 fn cname(&self) -> Option<&CStr> {
1278 self.inner.name.as_deref()
1282 #[stable(feature = "rust1", since = "1.0.0")]
1283 impl fmt::Debug for Thread {
1284 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1285 f.debug_struct("Thread").field("id", &self.id()).field("name", &self.name()).finish()
1289 ////////////////////////////////////////////////////////////////////////////////
1291 ////////////////////////////////////////////////////////////////////////////////
1293 /// A specialized [`Result`] type for threads.
1295 /// Indicates the manner in which a thread exited.
1297 /// The value contained in the `Result::Err` variant
1298 /// is the value the thread panicked with;
1299 /// that is, the argument the `panic!` macro was called with.
1300 /// Unlike with normal errors, this value doesn't implement
1301 /// the [`Error`](crate::error::Error) trait.
1303 /// Thus, a sensible way to handle a thread panic is to either:
1304 /// 1. `unwrap` the `Result<T>`, propagating the panic
1305 /// 2. or in case the thread is intended to be a subsystem boundary
1306 /// that is supposed to isolate system-level failures,
1307 /// match on the `Err` variant and handle the panic in an appropriate way.
1309 /// A thread that completes without panicking is considered to exit successfully.
1314 /// use std::thread;
1317 /// fn copy_in_thread() -> thread::Result<()> {
1318 /// thread::spawn(move || { fs::copy("foo.txt", "bar.txt").unwrap(); }).join()
1322 /// match copy_in_thread() {
1323 /// Ok(_) => println!("this is fine"),
1324 /// Err(_) => println!("thread panicked"),
1329 /// [`Result`]: ../../std/result/enum.Result.html
1330 #[stable(feature = "rust1", since = "1.0.0")]
1331 pub type Result<T> = crate::result::Result<T, Box<dyn Any + Send + 'static>>;
1333 // This packet is used to communicate the return value between the child thread
1334 // and the parent thread. Memory is shared through the `Arc` within and there's
1335 // no need for a mutex here because synchronization happens with `join()` (the
1336 // parent thread never reads this packet until the child has exited).
1338 // This packet itself is then stored into a `JoinInner` which in turns is placed
1339 // in `JoinHandle` and `JoinGuard`. Due to the usage of `UnsafeCell` we need to
1340 // manually worry about impls like Send and Sync. The type `T` should
1341 // already always be Send (otherwise the thread could not have been created) and
1342 // this type is inherently Sync because no methods take &self. Regardless,
1343 // however, we add inheriting impls for Send/Sync to this type to ensure it's
1344 // Send/Sync and that future modifications will still appropriately classify it.
1345 struct Packet<T>(Arc<UnsafeCell<Option<Result<T>>>>);
1347 unsafe impl<T: Send> Send for Packet<T> {}
1348 unsafe impl<T: Sync> Sync for Packet<T> {}
1350 /// Inner representation for JoinHandle
1351 struct JoinInner<T> {
1352 native: Option<imp::Thread>,
1357 impl<T> JoinInner<T> {
1358 fn join(&mut self) -> Result<T> {
1359 self.native.take().unwrap().join();
1360 unsafe { (*self.packet.0.get()).take().unwrap() }
1364 /// An owned permission to join on a thread (block on its termination).
1366 /// A `JoinHandle` *detaches* the associated thread when it is dropped, which
1367 /// means that there is no longer any handle to thread and no way to `join`
1370 /// Due to platform restrictions, it is not possible to [`Clone`] this
1371 /// handle: the ability to join a thread is a uniquely-owned permission.
1373 /// This `struct` is created by the [`thread::spawn`] function and the
1374 /// [`thread::Builder::spawn`] method.
1378 /// Creation from [`thread::spawn`]:
1381 /// use std::thread;
1383 /// let join_handle: thread::JoinHandle<_> = thread::spawn(|| {
1384 /// // some work here
1388 /// Creation from [`thread::Builder::spawn`]:
1391 /// use std::thread;
1393 /// let builder = thread::Builder::new();
1395 /// let join_handle: thread::JoinHandle<_> = builder.spawn(|| {
1396 /// // some work here
1400 /// Child being detached and outliving its parent:
1403 /// use std::thread;
1404 /// use std::time::Duration;
1406 /// let original_thread = thread::spawn(|| {
1407 /// let _detached_thread = thread::spawn(|| {
1408 /// // Here we sleep to make sure that the first thread returns before.
1409 /// thread::sleep(Duration::from_millis(10));
1410 /// // This will be called, even though the JoinHandle is dropped.
1411 /// println!("♫ Still alive ♫");
1415 /// original_thread.join().expect("The thread being joined has panicked");
1416 /// println!("Original thread is joined.");
1418 /// // We make sure that the new thread has time to run, before the main
1419 /// // thread returns.
1421 /// thread::sleep(Duration::from_millis(1000));
1424 /// [`Clone`]: ../../std/clone/trait.Clone.html
1425 /// [`thread::spawn`]: fn.spawn.html
1426 /// [`thread::Builder::spawn`]: struct.Builder.html#method.spawn
1427 #[stable(feature = "rust1", since = "1.0.0")]
1428 pub struct JoinHandle<T>(JoinInner<T>);
1430 #[stable(feature = "joinhandle_impl_send_sync", since = "1.29.0")]
1431 unsafe impl<T> Send for JoinHandle<T> {}
1432 #[stable(feature = "joinhandle_impl_send_sync", since = "1.29.0")]
1433 unsafe impl<T> Sync for JoinHandle<T> {}
1435 impl<T> JoinHandle<T> {
1436 /// Extracts a handle to the underlying thread.
1441 /// use std::thread;
1443 /// let builder = thread::Builder::new();
1445 /// let join_handle: thread::JoinHandle<_> = builder.spawn(|| {
1446 /// // some work here
1449 /// let thread = join_handle.thread();
1450 /// println!("thread id: {:?}", thread.id());
1452 #[stable(feature = "rust1", since = "1.0.0")]
1453 pub fn thread(&self) -> &Thread {
1457 /// Waits for the associated thread to finish.
1459 /// In terms of [atomic memory orderings], the completion of the associated
1460 /// thread synchronizes with this function returning. In other words, all
1461 /// operations performed by that thread are ordered before all
1462 /// operations that happen after `join` returns.
1464 /// If the child thread panics, [`Err`] is returned with the parameter given
1467 /// [`Err`]: ../../std/result/enum.Result.html#variant.Err
1468 /// [`panic`]: ../../std/macro.panic.html
1469 /// [atomic memory orderings]: ../../std/sync/atomic/index.html
1473 /// This function may panic on some platforms if a thread attempts to join
1474 /// itself or otherwise may create a deadlock with joining threads.
1479 /// use std::thread;
1481 /// let builder = thread::Builder::new();
1483 /// let join_handle: thread::JoinHandle<_> = builder.spawn(|| {
1484 /// // some work here
1486 /// join_handle.join().expect("Couldn't join on the associated thread");
1488 #[stable(feature = "rust1", since = "1.0.0")]
1489 pub fn join(mut self) -> Result<T> {
1494 impl<T> AsInner<imp::Thread> for JoinHandle<T> {
1495 fn as_inner(&self) -> &imp::Thread {
1496 self.0.native.as_ref().unwrap()
1500 impl<T> IntoInner<imp::Thread> for JoinHandle<T> {
1501 fn into_inner(self) -> imp::Thread {
1502 self.0.native.unwrap()
1506 #[stable(feature = "std_debug", since = "1.16.0")]
1507 impl<T> fmt::Debug for JoinHandle<T> {
1508 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1509 f.pad("JoinHandle { .. }")
1513 fn _assert_sync_and_send() {
1514 fn _assert_both<T: Send + Sync>() {}
1515 _assert_both::<JoinHandle<()>>();
1516 _assert_both::<Thread>();
1519 ////////////////////////////////////////////////////////////////////////////////
1521 ////////////////////////////////////////////////////////////////////////////////
1523 #[cfg(all(test, not(target_os = "emscripten")))]
1526 use crate::any::Any;
1529 use crate::sync::mpsc::{channel, Sender};
1530 use crate::thread::{self, ThreadId};
1531 use crate::time::Duration;
1533 // !!! These tests are dangerous. If something is buggy, they will hang, !!!
1534 // !!! instead of exiting cleanly. This might wedge the buildbots. !!!
1537 fn test_unnamed_thread() {
1538 thread::spawn(move || {
1539 assert!(thread::current().name().is_none());
1543 .expect("thread panicked");
1547 fn test_named_thread() {
1549 .name("ada lovelace".to_string())
1551 assert!(thread::current().name().unwrap() == "ada lovelace".to_string());
1560 fn test_invalid_named_thread() {
1561 let _ = Builder::new().name("ada l\0velace".to_string()).spawn(|| {});
1565 fn test_run_basic() {
1566 let (tx, rx) = channel();
1567 thread::spawn(move || {
1568 tx.send(()).unwrap();
1574 fn test_join_panic() {
1575 match thread::spawn(move || panic!()).join() {
1576 result::Result::Err(_) => (),
1577 result::Result::Ok(()) => panic!(),
1582 fn test_spawn_sched() {
1583 let (tx, rx) = channel();
1585 fn f(i: i32, tx: Sender<()>) {
1586 let tx = tx.clone();
1587 thread::spawn(move || {
1589 tx.send(()).unwrap();
1600 fn test_spawn_sched_childs_on_default_sched() {
1601 let (tx, rx) = channel();
1603 thread::spawn(move || {
1604 thread::spawn(move || {
1605 tx.send(()).unwrap();
1612 fn avoid_copying_the_body<F>(spawnfn: F)
1614 F: FnOnce(Box<dyn Fn() + Send>),
1616 let (tx, rx) = channel();
1618 let x: Box<_> = box 1;
1619 let x_in_parent = (&*x) as *const i32 as usize;
1621 spawnfn(Box::new(move || {
1622 let x_in_child = (&*x) as *const i32 as usize;
1623 tx.send(x_in_child).unwrap();
1626 let x_in_child = rx.recv().unwrap();
1627 assert_eq!(x_in_parent, x_in_child);
1631 fn test_avoid_copying_the_body_spawn() {
1632 avoid_copying_the_body(|v| {
1633 thread::spawn(move || v());
1638 fn test_avoid_copying_the_body_thread_spawn() {
1639 avoid_copying_the_body(|f| {
1640 thread::spawn(move || {
1647 fn test_avoid_copying_the_body_join() {
1648 avoid_copying_the_body(|f| {
1649 let _ = thread::spawn(move || f()).join();
1654 fn test_child_doesnt_ref_parent() {
1655 // If the child refcounts the parent thread, this will stack overflow when
1656 // climbing the thread tree to dereference each ancestor. (See #1789)
1657 // (well, it would if the constant were 8000+ - I lowered it to be more
1658 // valgrind-friendly. try this at home, instead..!)
1659 const GENERATIONS: u32 = 16;
1660 fn child_no(x: u32) -> Box<dyn Fn() + Send> {
1661 return Box::new(move || {
1662 if x < GENERATIONS {
1663 thread::spawn(move || child_no(x + 1)());
1667 thread::spawn(|| child_no(0)());
1671 fn test_simple_newsched_spawn() {
1672 thread::spawn(move || {});
1676 fn test_try_panic_message_static_str() {
1677 match thread::spawn(move || {
1678 panic!("static string");
1683 type T = &'static str;
1684 assert!(e.is::<T>());
1685 assert_eq!(*e.downcast::<T>().unwrap(), "static string");
1692 fn test_try_panic_message_owned_str() {
1693 match thread::spawn(move || {
1694 panic!("owned string".to_string());
1700 assert!(e.is::<T>());
1701 assert_eq!(*e.downcast::<T>().unwrap(), "owned string".to_string());
1708 fn test_try_panic_message_any() {
1709 match thread::spawn(move || {
1710 panic!(box 413u16 as Box<dyn Any + Send>);
1715 type T = Box<dyn Any + Send>;
1716 assert!(e.is::<T>());
1717 let any = e.downcast::<T>().unwrap();
1718 assert!(any.is::<u16>());
1719 assert_eq!(*any.downcast::<u16>().unwrap(), 413);
1726 fn test_try_panic_message_unit_struct() {
1729 match thread::spawn(move || panic!(Juju)).join() {
1730 Err(ref e) if e.is::<Juju>() => {}
1731 Err(_) | Ok(()) => panic!(),
1736 fn test_park_timeout_unpark_before() {
1738 thread::current().unpark();
1739 thread::park_timeout(Duration::from_millis(u32::MAX as u64));
1744 fn test_park_timeout_unpark_not_called() {
1746 thread::park_timeout(Duration::from_millis(10));
1751 fn test_park_timeout_unpark_called_other_thread() {
1753 let th = thread::current();
1755 let _guard = thread::spawn(move || {
1756 super::sleep(Duration::from_millis(50));
1760 thread::park_timeout(Duration::from_millis(u32::MAX as u64));
1765 fn sleep_ms_smoke() {
1766 thread::sleep(Duration::from_millis(2));
1770 fn test_size_of_option_thread_id() {
1771 assert_eq!(mem::size_of::<Option<ThreadId>>(), mem::size_of::<ThreadId>());
1775 fn test_thread_id_equal() {
1776 assert!(thread::current().id() == thread::current().id());
1780 fn test_thread_id_not_equal() {
1781 let spawned_id = thread::spawn(|| thread::current().id()).join().unwrap();
1782 assert!(thread::current().id() != spawned_id);
1785 // NOTE: the corresponding test for stderr is in ui/thread-stderr, due
1786 // to the test harness apparently interfering with stderr configuration.