1 // Copyright 2014 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
13 //! ## The threading model
15 //! An executing Rust program consists of a collection of native OS threads,
16 //! each with their own stack and local state. Threads can be named, and
17 //! provide some built-in support for low-level synchronization.
19 //! Communication between threads can be done through
20 //! [channels], Rust's message-passing types, along with [other forms of thread
21 //! synchronization](../../std/sync/index.html) and shared-memory data
22 //! structures. In particular, types that are guaranteed to be
23 //! threadsafe are easily shared between threads using the
24 //! atomically-reference-counted container, [`Arc`].
26 //! Fatal logic errors in Rust cause *thread panic*, during which
27 //! a thread will unwind the stack, running destructors and freeing
28 //! owned resources. While not meant as a 'try/catch' mechanism, panics
29 //! in Rust can nonetheless be caught (unless compiling with `panic=abort`) with
30 //! [`catch_unwind`](../../std/panic/fn.catch_unwind.html) and recovered
31 //! from, or alternatively be resumed with
32 //! [`resume_unwind`](../../std/panic/fn.resume_unwind.html). If the panic
33 //! is not caught the thread will exit, but the panic may optionally be
34 //! detected from a different thread with [`join`]. If the main thread panics
35 //! without the panic being caught, the application will exit with a
36 //! non-zero exit code.
38 //! When the main thread of a Rust program terminates, the entire program shuts
39 //! down, even if other threads are still running. However, this module provides
40 //! convenient facilities for automatically waiting for the termination of a
41 //! child thread (i.e., join).
43 //! ## Spawning a thread
45 //! A new thread can be spawned using the [`thread::spawn`][`spawn`] function:
50 //! thread::spawn(move || {
55 //! In this example, the spawned thread is "detached" from the current
56 //! thread. This means that it can outlive its parent (the thread that spawned
57 //! it), unless this parent is the main thread.
59 //! The parent thread can also wait on the completion of the child
60 //! thread; a call to [`spawn`] produces a [`JoinHandle`], which provides
61 //! a `join` method for waiting:
66 //! let child = thread::spawn(move || {
70 //! let res = child.join();
73 //! The [`join`] method returns a [`thread::Result`] containing [`Ok`] of the final
74 //! value produced by the child thread, or [`Err`] of the value given to
75 //! a call to [`panic!`] if the child panicked.
77 //! ## Configuring threads
79 //! A new thread can be configured before it is spawned via the [`Builder`] type,
80 //! which currently allows you to set the name and stack size for the child thread:
83 //! # #![allow(unused_must_use)]
86 //! thread::Builder::new().name("child1".to_string()).spawn(move || {
87 //! println!("Hello, world!");
91 //! ## The `Thread` type
93 //! Threads are represented via the [`Thread`] type, which you can get in one of
96 //! * By spawning a new thread, e.g. using the [`thread::spawn`][`spawn`]
97 //! function, and calling [`thread`][`JoinHandle::thread`] on the [`JoinHandle`].
98 //! * By requesting the current thread, using the [`thread::current`] function.
100 //! The [`thread::current`] function is available even for threads not spawned
101 //! by the APIs of this module.
103 //! ## Thread-local storage
105 //! This module also provides an implementation of thread-local storage for Rust
106 //! programs. Thread-local storage is a method of storing data into a global
107 //! variable that each thread in the program will have its own copy of.
108 //! Threads do not share this data, so accesses do not need to be synchronized.
110 //! A thread-local key owns the value it contains and will destroy the value when the
111 //! thread exits. It is created with the [`thread_local!`] macro and can contain any
112 //! value that is `'static` (no borrowed pointers). It provides an accessor function,
113 //! [`with`], that yields a shared reference to the value to the specified
114 //! closure. Thread-local keys allow only shared access to values, as there would be no
115 //! way to guarantee uniqueness if mutable borrows were allowed. Most values
116 //! will want to make use of some form of **interior mutability** through the
117 //! [`Cell`] or [`RefCell`] types.
119 //! ## Naming threads
121 //! Threads are able to have associated names for identification purposes. By default, spawned
122 //! threads are unnamed. To specify a name for a thread, build the thread with [`Builder`] and pass
123 //! the desired thread name to [`Builder::name`]. To retrieve the thread name from within the
124 //! thread, use [`Thread::name`]. A couple examples of where the name of a thread gets used:
126 //! * If a panic occurs in a named thread, the thread name will be printed in the panic message.
127 //! * The thread name is provided to the OS where applicable (e.g. `pthread_setname_np` in
128 //! unix-like platforms).
132 //! The default stack size for spawned threads is 2 MiB, though this particular stack size is
133 //! subject to change in the future. There are two ways to manually specify the stack size for
136 //! * Build the thread with [`Builder`] and pass the desired stack size to [`Builder::stack_size`].
137 //! * Set the `RUST_MIN_STACK` environment variable to an integer representing the desired stack
138 //! size (in bytes). Note that setting [`Builder::stack_size`] will override this.
140 //! Note that the stack size of the main thread is *not* determined by Rust.
142 //! [channels]: ../../std/sync/mpsc/index.html
143 //! [`Arc`]: ../../std/sync/struct.Arc.html
144 //! [`spawn`]: ../../std/thread/fn.spawn.html
145 //! [`JoinHandle`]: ../../std/thread/struct.JoinHandle.html
146 //! [`JoinHandle::thread`]: ../../std/thread/struct.JoinHandle.html#method.thread
147 //! [`join`]: ../../std/thread/struct.JoinHandle.html#method.join
148 //! [`Result`]: ../../std/result/enum.Result.html
149 //! [`Ok`]: ../../std/result/enum.Result.html#variant.Ok
150 //! [`Err`]: ../../std/result/enum.Result.html#variant.Err
151 //! [`panic!`]: ../../std/macro.panic.html
152 //! [`Builder`]: ../../std/thread/struct.Builder.html
153 //! [`Builder::stack_size`]: ../../std/thread/struct.Builder.html#method.stack_size
154 //! [`Builder::name`]: ../../std/thread/struct.Builder.html#method.name
155 //! [`thread::current`]: ../../std/thread/fn.current.html
156 //! [`thread::Result`]: ../../std/thread/type.Result.html
157 //! [`Thread`]: ../../std/thread/struct.Thread.html
158 //! [`park`]: ../../std/thread/fn.park.html
159 //! [`unpark`]: ../../std/thread/struct.Thread.html#method.unpark
160 //! [`Thread::name`]: ../../std/thread/struct.Thread.html#method.name
161 //! [`thread::park_timeout`]: ../../std/thread/fn.park_timeout.html
162 //! [`Cell`]: ../cell/struct.Cell.html
163 //! [`RefCell`]: ../cell/struct.RefCell.html
164 //! [`thread_local!`]: ../macro.thread_local.html
165 //! [`with`]: struct.LocalKey.html#method.with
167 #![stable(feature = "rust1", since = "1.0.0")]
170 use cell::UnsafeCell;
171 use ffi::{CStr, CString};
177 use sync::{Mutex, Condvar, Arc};
178 use sync::atomic::AtomicUsize;
179 use sync::atomic::Ordering::SeqCst;
180 use sys::thread as imp;
181 use sys_common::mutex;
182 use sys_common::thread_info;
183 use sys_common::thread;
184 use sys_common::{AsInner, IntoInner};
187 ////////////////////////////////////////////////////////////////////////////////
188 // Thread-local storage
189 ////////////////////////////////////////////////////////////////////////////////
191 #[macro_use] mod local;
193 #[stable(feature = "rust1", since = "1.0.0")]
194 pub use self::local::{LocalKey, AccessError};
196 // The types used by the thread_local! macro to access TLS keys. Note that there
197 // are two types, the "OS" type and the "fast" type. The OS thread local key
198 // type is accessed via platform-specific API calls and is slow, while the fast
199 // key type is accessed via code generated via LLVM, where TLS keys are set up
200 // by the elf linker. Note that the OS TLS type is always available: on macOS
201 // the standard library is compiled with support for older platform versions
202 // where fast TLS was not available; end-user code is compiled with fast TLS
203 // where available, but both are needed.
205 #[unstable(feature = "libstd_thread_internals", issue = "0")]
206 #[cfg(all(target_arch = "wasm32", not(target_feature = "atomics")))]
207 #[doc(hidden)] pub use self::local::statik::Key as __StaticLocalKeyInner;
208 #[unstable(feature = "libstd_thread_internals", issue = "0")]
209 #[cfg(target_thread_local)]
210 #[doc(hidden)] pub use self::local::fast::Key as __FastLocalKeyInner;
211 #[unstable(feature = "libstd_thread_internals", issue = "0")]
212 #[doc(hidden)] pub use self::local::os::Key as __OsLocalKeyInner;
214 ////////////////////////////////////////////////////////////////////////////////
216 ////////////////////////////////////////////////////////////////////////////////
218 /// Thread factory, which can be used in order to configure the properties of
221 /// Methods can be chained on it in order to configure it.
223 /// The two configurations available are:
225 /// - [`name`]: specifies an [associated name for the thread][naming-threads]
226 /// - [`stack_size`]: specifies the [desired stack size for the thread][stack-size]
228 /// The [`spawn`] method will take ownership of the builder and create an
229 /// [`io::Result`] to the thread handle with the given configuration.
231 /// The [`thread::spawn`] free function uses a `Builder` with default
232 /// configuration and [`unwrap`]s its return value.
234 /// You may want to use [`spawn`] instead of [`thread::spawn`], when you want
235 /// to recover from a failure to launch a thread, indeed the free function will
236 /// panick where the `Builder` method will return a [`io::Result`].
243 /// let builder = thread::Builder::new();
245 /// let handler = builder.spawn(|| {
249 /// handler.join().unwrap();
252 /// [`thread::spawn`]: ../../std/thread/fn.spawn.html
253 /// [`stack_size`]: ../../std/thread/struct.Builder.html#method.stack_size
254 /// [`name`]: ../../std/thread/struct.Builder.html#method.name
255 /// [`spawn`]: ../../std/thread/struct.Builder.html#method.spawn
256 /// [`io::Result`]: ../../std/io/type.Result.html
257 /// [`unwrap`]: ../../std/result/enum.Result.html#method.unwrap
258 /// [naming-threads]: ./index.html#naming-threads
259 /// [stack-size]: ./index.html#stack-size
260 #[stable(feature = "rust1", since = "1.0.0")]
263 // A name for the thread-to-be, for identification in panic messages
264 name: Option<String>,
265 // The size of the stack for the spawned thread in bytes
266 stack_size: Option<usize>,
270 /// Generates the base configuration for spawning a thread, from which
271 /// configuration methods can be chained.
278 /// let builder = thread::Builder::new()
279 /// .name("foo".into())
282 /// let handler = builder.spawn(|| {
286 /// handler.join().unwrap();
288 #[stable(feature = "rust1", since = "1.0.0")]
289 pub fn new() -> Builder {
296 /// Names the thread-to-be. Currently the name is used for identification
297 /// only in panic messages.
299 /// The name must not contain null bytes (`\0`).
301 /// For more information about named threads, see
302 /// [this module-level documentation][naming-threads].
309 /// let builder = thread::Builder::new()
310 /// .name("foo".into());
312 /// let handler = builder.spawn(|| {
313 /// assert_eq!(thread::current().name(), Some("foo"))
316 /// handler.join().unwrap();
319 /// [naming-threads]: ./index.html#naming-threads
320 #[stable(feature = "rust1", since = "1.0.0")]
321 pub fn name(mut self, name: String) -> Builder {
322 self.name = Some(name);
326 /// Sets the size of the stack (in bytes) for the new thread.
328 /// The actual stack size may be greater than this value if
329 /// the platform specifies minimal stack size.
331 /// For more information about the stack size for threads, see
332 /// [this module-level documentation][stack-size].
339 /// let builder = thread::Builder::new().stack_size(32 * 1024);
342 /// [stack-size]: ./index.html#stack-size
343 #[stable(feature = "rust1", since = "1.0.0")]
344 pub fn stack_size(mut self, size: usize) -> Builder {
345 self.stack_size = Some(size);
349 /// Spawns a new thread by taking ownership of the `Builder`, and returns an
350 /// [`io::Result`] to its [`JoinHandle`].
352 /// The spawned thread may outlive the caller (unless the caller thread
353 /// is the main thread; the whole process is terminated when the main
354 /// thread finishes). The join handle can be used to block on
355 /// termination of the child thread, including recovering its panics.
357 /// For a more complete documentation see [`thread::spawn`][`spawn`].
361 /// Unlike the [`spawn`] free function, this method yields an
362 /// [`io::Result`] to capture any failure to create the thread at
365 /// [`spawn`]: ../../std/thread/fn.spawn.html
366 /// [`io::Result`]: ../../std/io/type.Result.html
367 /// [`JoinHandle`]: ../../std/thread/struct.JoinHandle.html
371 /// Panics if a thread name was set and it contained null bytes.
378 /// let builder = thread::Builder::new();
380 /// let handler = builder.spawn(|| {
384 /// handler.join().unwrap();
386 #[stable(feature = "rust1", since = "1.0.0")]
387 pub fn spawn<F, T>(self, f: F) -> io::Result<JoinHandle<T>> where
388 F: FnOnce() -> T, F: Send + 'static, T: Send + 'static
390 unsafe { self.spawn_unchecked(f) }
393 /// Spawns a new thread without any lifetime restrictions by taking ownership
394 /// of the `Builder`, and returns an [`io::Result`] to its [`JoinHandle`].
396 /// The spawned thread may outlive the caller (unless the caller thread
397 /// is the main thread; the whole process is terminated when the main
398 /// thread finishes). The join handle can be used to block on
399 /// termination of the child thread, including recovering its panics.
401 /// This method is identical to [`thread::Builder::spawn`][`Builder::spawn`],
402 /// except for the relaxed lifetime bounds, which render it unsafe.
403 /// For a more complete documentation see [`thread::spawn`][`spawn`].
407 /// Unlike the [`spawn`] free function, this method yields an
408 /// [`io::Result`] to capture any failure to create the thread at
413 /// Panics if a thread name was set and it contained null bytes.
417 /// The caller has to ensure that no references in the supplied thread closure
418 /// or its return type can outlive the spawned thread's lifetime. This can be
419 /// guaranteed in two ways:
421 /// - ensure that [`join`][`JoinHandle::join`] is called before any referenced
423 /// - use only types with `'static` lifetime bounds, i.e. those with no or only
424 /// `'static` references (both [`thread::Builder::spawn`][`Builder::spawn`]
425 /// and [`thread::spawn`][`spawn`] enforce this property statically)
430 /// #![feature(thread_spawn_unchecked)]
433 /// let builder = thread::Builder::new();
436 /// let thread_x = &x;
438 /// let handler = unsafe {
439 /// builder.spawn_unchecked(move || {
440 /// println!("x = {}", *thread_x);
444 /// // caller has to ensure `join()` is called, otherwise
445 /// // it is possible to access freed memory if `x` gets
446 /// // dropped before the thread closure is executed!
447 /// handler.join().unwrap();
450 /// [`spawn`]: ../../std/thread/fn.spawn.html
451 /// [`Builder::spawn`]: ../../std/thread/struct.Builder.html#method.spawn
452 /// [`io::Result`]: ../../std/io/type.Result.html
453 /// [`JoinHandle`]: ../../std/thread/struct.JoinHandle.html
454 #[unstable(feature = "thread_spawn_unchecked", issue = "55132")]
455 pub unsafe fn spawn_unchecked<F, T>(self, f: F) -> io::Result<JoinHandle<T>> where
456 F: FnOnce() -> T, F: Send, T: Send
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>>>>
466 = Arc::new(UnsafeCell::new(None));
467 let their_packet = my_packet.clone();
470 if let Some(name) = their_thread.cname() {
471 imp::Thread::set_name(name);
474 thread_info::set(imp::guard::current(), their_thread);
475 #[cfg(feature = "backtrace")]
476 let try_result = panic::catch_unwind(panic::AssertUnwindSafe(|| {
477 ::sys_common::backtrace::__rust_begin_short_backtrace(f)
479 #[cfg(not(feature = "backtrace"))]
480 let try_result = panic::catch_unwind(panic::AssertUnwindSafe(f));
481 *their_packet.get() = Some(try_result);
484 Ok(JoinHandle(JoinInner {
485 native: Some(imp::Thread::new(stack_size, Box::new(main))?),
487 packet: Packet(my_packet),
492 ////////////////////////////////////////////////////////////////////////////////
494 ////////////////////////////////////////////////////////////////////////////////
496 /// Spawns a new thread, returning a [`JoinHandle`] for it.
498 /// The join handle will implicitly *detach* the child thread upon being
499 /// dropped. In this case, the child thread may outlive the parent (unless
500 /// the parent thread is the main thread; the whole process is terminated when
501 /// the main thread finishes). Additionally, the join handle provides a [`join`]
502 /// method that can be used to join the child thread. If the child thread
503 /// panics, [`join`] will return an [`Err`] containing the argument given to
506 /// This will create a thread using default parameters of [`Builder`], if you
507 /// want to specify the stack size or the name of the thread, use this API
510 /// As you can see in the signature of `spawn` there are two constraints on
511 /// both the closure given to `spawn` and its return value, let's explain them:
513 /// - The `'static` constraint means that the closure and its return value
514 /// must have a lifetime of the whole program execution. The reason for this
515 /// is that threads can `detach` and outlive the lifetime they have been
517 /// Indeed if the thread, and by extension its return value, can outlive their
518 /// caller, we need to make sure that they will be valid afterwards, and since
519 /// we *can't* know when it will return we need to have them valid as long as
520 /// possible, that is until the end of the program, hence the `'static`
522 /// - The [`Send`] constraint is because the closure will need to be passed
523 /// *by value* from the thread where it is spawned to the new thread. Its
524 /// return value will need to be passed from the new thread to the thread
525 /// where it is `join`ed.
526 /// As a reminder, the [`Send`] marker trait expresses that it is safe to be
527 /// passed from thread to thread. [`Sync`] expresses that it is safe to have a
528 /// reference be passed from thread to thread.
532 /// Panics if the OS fails to create a thread; use [`Builder::spawn`]
533 /// to recover from such errors.
537 /// Creating a thread.
542 /// let handler = thread::spawn(|| {
546 /// handler.join().unwrap();
549 /// As mentioned in the module documentation, threads are usually made to
550 /// communicate using [`channels`], here is how it usually looks.
552 /// This example also shows how to use `move`, in order to give ownership
553 /// of values to a thread.
557 /// use std::sync::mpsc::channel;
559 /// let (tx, rx) = channel();
561 /// let sender = thread::spawn(move || {
562 /// tx.send("Hello, thread".to_owned())
563 /// .expect("Unable to send on channel");
566 /// let receiver = thread::spawn(move || {
567 /// let value = rx.recv().expect("Unable to receive from channel");
568 /// println!("{}", value);
571 /// sender.join().expect("The sender thread has panicked");
572 /// receiver.join().expect("The receiver thread has panicked");
575 /// A thread can also return a value through its [`JoinHandle`], you can use
576 /// this to make asynchronous computations (futures might be more appropriate
582 /// let computation = thread::spawn(|| {
583 /// // Some expensive computation.
587 /// let result = computation.join().unwrap();
588 /// println!("{}", result);
591 /// [`channels`]: ../../std/sync/mpsc/index.html
592 /// [`JoinHandle`]: ../../std/thread/struct.JoinHandle.html
593 /// [`join`]: ../../std/thread/struct.JoinHandle.html#method.join
594 /// [`Err`]: ../../std/result/enum.Result.html#variant.Err
595 /// [`panic`]: ../../std/macro.panic.html
596 /// [`Builder::spawn`]: ../../std/thread/struct.Builder.html#method.spawn
597 /// [`Builder`]: ../../std/thread/struct.Builder.html
598 /// [`Send`]: ../../std/marker/trait.Send.html
599 /// [`Sync`]: ../../std/marker/trait.Sync.html
600 #[stable(feature = "rust1", since = "1.0.0")]
601 pub fn spawn<F, T>(f: F) -> JoinHandle<T> where
602 F: FnOnce() -> T, F: Send + 'static, T: Send + 'static
604 Builder::new().spawn(f).unwrap()
607 /// Gets a handle to the thread that invokes it.
611 /// Getting a handle to the current thread with `thread::current()`:
616 /// let handler = thread::Builder::new()
617 /// .name("named thread".into())
619 /// let handle = thread::current();
620 /// assert_eq!(handle.name(), Some("named thread"));
624 /// handler.join().unwrap();
626 #[stable(feature = "rust1", since = "1.0.0")]
627 pub fn current() -> Thread {
628 thread_info::current_thread().expect("use of std::thread::current() is not \
629 possible after the thread's local \
630 data has been destroyed")
633 /// Cooperatively gives up a timeslice to the OS scheduler.
635 /// This is used when the programmer knows that the thread will have nothing
636 /// to do for some time, and thus avoid wasting computing time.
638 /// For example when polling on a resource, it is common to check that it is
639 /// available, and if not to yield in order to avoid busy waiting.
641 /// Thus the pattern of `yield`ing after a failed poll is rather common when
642 /// implementing low-level shared resources or synchronization primitives.
644 /// However programmers will usually prefer to use [`channel`]s, [`Condvar`]s,
645 /// [`Mutex`]es or [`join`] for their synchronization routines, as they avoid
646 /// thinking about thread scheduling.
648 /// Note that [`channel`]s for example are implemented using this primitive.
649 /// Indeed when you call `send` or `recv`, which are blocking, they will yield
650 /// if the channel is not available.
657 /// thread::yield_now();
660 /// [`channel`]: ../../std/sync/mpsc/index.html
661 /// [`spawn`]: ../../std/thread/fn.spawn.html
662 /// [`join`]: ../../std/thread/struct.JoinHandle.html#method.join
663 /// [`Mutex`]: ../../std/sync/struct.Mutex.html
664 /// [`Condvar`]: ../../std/sync/struct.Condvar.html
665 #[stable(feature = "rust1", since = "1.0.0")]
667 imp::Thread::yield_now()
670 /// Determines whether the current thread is unwinding because of panic.
672 /// A common use of this feature is to poison shared resources when writing
673 /// unsafe code, by checking `panicking` when the `drop` is called.
675 /// This is usually not needed when writing safe code, as [`Mutex`es][Mutex]
676 /// already poison themselves when a thread panics while holding the lock.
678 /// This can also be used in multithreaded applications, in order to send a
679 /// message to other threads warning that a thread has panicked (e.g. for
680 /// monitoring purposes).
687 /// struct SomeStruct;
689 /// impl Drop for SomeStruct {
690 /// fn drop(&mut self) {
691 /// if thread::panicking() {
692 /// println!("dropped while unwinding");
694 /// println!("dropped while not unwinding");
701 /// let a = SomeStruct;
706 /// let b = SomeStruct;
711 /// [Mutex]: ../../std/sync/struct.Mutex.html
713 #[stable(feature = "rust1", since = "1.0.0")]
714 pub fn panicking() -> bool {
715 panicking::panicking()
718 /// Puts the current thread to sleep for at least the specified amount of time.
720 /// The thread may sleep longer than the duration specified due to scheduling
721 /// specifics or platform-dependent functionality. It will never sleep less.
723 /// # Platform-specific behavior
725 /// On Unix platforms, the underlying syscall may be interrupted by a
726 /// spurious wakeup or signal handler. To ensure the sleep occurs for at least
727 /// the specified duration, this function may invoke that system call multiple
735 /// // Let's sleep for 2 seconds:
736 /// thread::sleep_ms(2000);
738 #[stable(feature = "rust1", since = "1.0.0")]
739 #[rustc_deprecated(since = "1.6.0", reason = "replaced by `std::thread::sleep`")]
740 pub fn sleep_ms(ms: u32) {
741 sleep(Duration::from_millis(ms as u64))
744 /// Puts the current thread to sleep for at least the specified amount of time.
746 /// The thread may sleep longer than the duration specified due to scheduling
747 /// specifics or platform-dependent functionality. It will never sleep less.
749 /// # Platform-specific behavior
751 /// On Unix platforms, the underlying syscall may be interrupted by a
752 /// spurious wakeup or signal handler. To ensure the sleep occurs for at least
753 /// the specified duration, this function may invoke that system call multiple
755 /// Platforms which do not support nanosecond precision for sleeping will
756 /// have `dur` rounded up to the nearest granularity of time they can sleep for.
761 /// use std::{thread, time};
763 /// let ten_millis = time::Duration::from_millis(10);
764 /// let now = time::Instant::now();
766 /// thread::sleep(ten_millis);
768 /// assert!(now.elapsed() >= ten_millis);
770 #[stable(feature = "thread_sleep", since = "1.4.0")]
771 pub fn sleep(dur: Duration) {
772 imp::Thread::sleep(dur)
775 // constants for park/unpark
776 const EMPTY: usize = 0;
777 const PARKED: usize = 1;
778 const NOTIFIED: usize = 2;
780 /// Blocks unless or until the current thread's token is made available.
782 /// A call to `park` does not guarantee that the thread will remain parked
783 /// forever, and callers should be prepared for this possibility.
785 /// # park and unpark
787 /// Every thread is equipped with some basic low-level blocking support, via the
788 /// [`thread::park`][`park`] function and [`thread::Thread::unpark`][`unpark`]
789 /// method. [`park`] blocks the current thread, which can then be resumed from
790 /// another thread by calling the [`unpark`] method on the blocked thread's
793 /// Conceptually, each [`Thread`] handle has an associated token, which is
794 /// initially not present:
796 /// * The [`thread::park`][`park`] function blocks the current thread unless or
797 /// until the token is available for its thread handle, at which point it
798 /// atomically consumes the token. It may also return *spuriously*, without
799 /// consuming the token. [`thread::park_timeout`] does the same, but allows
800 /// specifying a maximum time to block the thread for.
802 /// * The [`unpark`] method on a [`Thread`] atomically makes the token available
803 /// if it wasn't already. Because the token is initially absent, [`unpark`]
804 /// followed by [`park`] will result in the second call returning immediately.
806 /// In other words, each [`Thread`] acts a bit like a spinlock that can be
807 /// locked and unlocked using `park` and `unpark`.
809 /// The API is typically used by acquiring a handle to the current thread,
810 /// placing that handle in a shared data structure so that other threads can
811 /// find it, and then `park`ing. When some desired condition is met, another
812 /// thread calls [`unpark`] on the handle.
814 /// The motivation for this design is twofold:
816 /// * It avoids the need to allocate mutexes and condvars when building new
817 /// synchronization primitives; the threads already provide basic
818 /// blocking/signaling.
820 /// * It can be implemented very efficiently on many platforms.
826 /// use std::time::Duration;
828 /// let parked_thread = thread::Builder::new()
830 /// println!("Parking thread");
832 /// println!("Thread unparked");
836 /// // Let some time pass for the thread to be spawned.
837 /// thread::sleep(Duration::from_millis(10));
839 /// // There is no race condition here, if `unpark`
840 /// // happens first, `park` will return immediately.
841 /// println!("Unpark the thread");
842 /// parked_thread.thread().unpark();
844 /// parked_thread.join().unwrap();
847 /// [`Thread`]: ../../std/thread/struct.Thread.html
848 /// [`park`]: ../../std/thread/fn.park.html
849 /// [`unpark`]: ../../std/thread/struct.Thread.html#method.unpark
850 /// [`thread::park_timeout`]: ../../std/thread/fn.park_timeout.html
852 // The implementation currently uses the trivial strategy of a Mutex+Condvar
853 // with wakeup flag, which does not actually allow spurious wakeups. In the
854 // future, this will be implemented in a more efficient way, perhaps along the lines of
855 // http://cr.openjdk.java.net/~stefank/6989984.1/raw_files/new/src/os/linux/vm/os_linux.cpp
856 // or futuxes, and in either case may allow spurious wakeups.
857 #[stable(feature = "rust1", since = "1.0.0")]
859 let thread = current();
861 // If we were previously notified then we consume this notification and
863 if thread.inner.state.compare_exchange(NOTIFIED, EMPTY, SeqCst, SeqCst).is_ok() {
867 // Otherwise we need to coordinate going to sleep
868 let mut m = thread.inner.lock.lock().unwrap();
869 match thread.inner.state.compare_exchange(EMPTY, PARKED, SeqCst, SeqCst) {
872 // We must read here, even though we know it will be `NOTIFIED`.
873 // This is because `unpark` may have been called again since we read
874 // `NOTIFIED` in the `compare_exchange` above. We must perform an
875 // acquire operation that synchronizes with that `unpark` to observe
876 // any writes it made before the call to unpark. To do that we must
877 // read from the write it made to `state`.
878 let old = thread.inner.state.swap(EMPTY, SeqCst);
879 assert_eq!(old, NOTIFIED, "park state changed unexpectedly");
881 } // should consume this notification, so prohibit spurious wakeups in next park.
882 Err(_) => panic!("inconsistent park state"),
885 m = thread.inner.cvar.wait(m).unwrap();
886 match thread.inner.state.compare_exchange(NOTIFIED, EMPTY, SeqCst, SeqCst) {
887 Ok(_) => return, // got a notification
888 Err(_) => {} // spurious wakeup, go back to sleep
893 /// Use [`park_timeout`].
895 /// Blocks unless or until the current thread's token is made available or
896 /// the specified duration has been reached (may wake spuriously).
898 /// The semantics of this function are equivalent to [`park`] except
899 /// that the thread will be blocked for roughly no longer than `dur`. This
900 /// method should not be used for precise timing due to anomalies such as
901 /// preemption or platform differences that may not cause the maximum
902 /// amount of time waited to be precisely `ms` long.
904 /// See the [park documentation][`park`] for more detail.
906 /// [`park_timeout`]: fn.park_timeout.html
907 /// [`park`]: ../../std/thread/fn.park.html
908 #[stable(feature = "rust1", since = "1.0.0")]
909 #[rustc_deprecated(since = "1.6.0", reason = "replaced by `std::thread::park_timeout`")]
910 pub fn park_timeout_ms(ms: u32) {
911 park_timeout(Duration::from_millis(ms as u64))
914 /// Blocks unless or until the current thread's token is made available or
915 /// the specified duration has been reached (may wake spuriously).
917 /// The semantics of this function are equivalent to [`park`][park] except
918 /// that the thread will be blocked for roughly no longer than `dur`. This
919 /// method should not be used for precise timing due to anomalies such as
920 /// preemption or platform differences that may not cause the maximum
921 /// amount of time waited to be precisely `dur` long.
923 /// See the [park documentation][park] for more details.
925 /// # Platform-specific behavior
927 /// Platforms which do not support nanosecond precision for sleeping will have
928 /// `dur` rounded up to the nearest granularity of time they can sleep for.
932 /// Waiting for the complete expiration of the timeout:
935 /// use std::thread::park_timeout;
936 /// use std::time::{Instant, Duration};
938 /// let timeout = Duration::from_secs(2);
939 /// let beginning_park = Instant::now();
941 /// let mut timeout_remaining = timeout;
943 /// park_timeout(timeout_remaining);
944 /// let elapsed = beginning_park.elapsed();
945 /// if elapsed >= timeout {
948 /// println!("restarting park_timeout after {:?}", elapsed);
949 /// timeout_remaining = timeout - elapsed;
953 /// [park]: fn.park.html
954 #[stable(feature = "park_timeout", since = "1.4.0")]
955 pub fn park_timeout(dur: Duration) {
956 let thread = current();
958 // Like `park` above we have a fast path for an already-notified thread, and
959 // afterwards we start coordinating for a sleep.
961 if thread.inner.state.compare_exchange(NOTIFIED, EMPTY, SeqCst, SeqCst).is_ok() {
964 let m = thread.inner.lock.lock().unwrap();
965 match thread.inner.state.compare_exchange(EMPTY, PARKED, SeqCst, SeqCst) {
968 // We must read again here, see `park`.
969 let old = thread.inner.state.swap(EMPTY, SeqCst);
970 assert_eq!(old, NOTIFIED, "park state changed unexpectedly");
972 } // should consume this notification, so prohibit spurious wakeups in next park.
973 Err(_) => panic!("inconsistent park_timeout state"),
976 // Wait with a timeout, and if we spuriously wake up or otherwise wake up
977 // from a notification we just want to unconditionally set the state back to
978 // empty, either consuming a notification or un-flagging ourselves as
980 let (_m, _result) = thread.inner.cvar.wait_timeout(m, dur).unwrap();
981 match thread.inner.state.swap(EMPTY, SeqCst) {
982 NOTIFIED => {} // got a notification, hurray!
983 PARKED => {} // no notification, alas
984 n => panic!("inconsistent park_timeout state: {}", n),
988 ////////////////////////////////////////////////////////////////////////////////
990 ////////////////////////////////////////////////////////////////////////////////
992 /// A unique identifier for a running thread.
994 /// A `ThreadId` is an opaque object that has a unique value for each thread
995 /// that creates one. `ThreadId`s are not guaranteed to correspond to a thread's
996 /// system-designated identifier. A `ThreadId` can be retrieved from the [`id`]
997 /// method on a [`Thread`].
1002 /// use std::thread;
1004 /// let other_thread = thread::spawn(|| {
1005 /// thread::current().id()
1008 /// let other_thread_id = other_thread.join().unwrap();
1009 /// assert!(thread::current().id() != other_thread_id);
1012 /// [`id`]: ../../std/thread/struct.Thread.html#method.id
1013 /// [`Thread`]: ../../std/thread/struct.Thread.html
1014 #[stable(feature = "thread_id", since = "1.19.0")]
1015 #[derive(Eq, PartialEq, Clone, Copy, Hash, Debug)]
1016 pub struct ThreadId(u64);
1019 // Generate a new unique thread ID.
1020 fn new() -> ThreadId {
1021 // We never call `GUARD.init()`, so it is UB to attempt to
1022 // acquire this mutex reentrantly!
1023 static GUARD: mutex::Mutex = mutex::Mutex::new();
1024 static mut COUNTER: u64 = 0;
1027 let _guard = GUARD.lock();
1029 // If we somehow use up all our bits, panic so that we're not
1030 // covering up subtle bugs of IDs being reused.
1031 if COUNTER == ::u64::MAX {
1032 panic!("failed to generate unique thread ID: bitspace exhausted");
1043 ////////////////////////////////////////////////////////////////////////////////
1045 ////////////////////////////////////////////////////////////////////////////////
1047 /// The internal representation of a `Thread` handle
1049 name: Option<CString>, // Guaranteed to be UTF-8
1052 // state for thread park/unpark
1059 #[stable(feature = "rust1", since = "1.0.0")]
1060 /// A handle to a thread.
1062 /// Threads are represented via the `Thread` type, which you can get in one of
1065 /// * By spawning a new thread, e.g. using the [`thread::spawn`][`spawn`]
1066 /// function, and calling [`thread`][`JoinHandle::thread`] on the
1068 /// * By requesting the current thread, using the [`thread::current`] function.
1070 /// The [`thread::current`] function is available even for threads not spawned
1071 /// by the APIs of this module.
1073 /// There is usually no need to create a `Thread` struct yourself, one
1074 /// should instead use a function like `spawn` to create new threads, see the
1075 /// docs of [`Builder`] and [`spawn`] for more details.
1077 /// [`Builder`]: ../../std/thread/struct.Builder.html
1078 /// [`JoinHandle::thread`]: ../../std/thread/struct.JoinHandle.html#method.thread
1079 /// [`JoinHandle`]: ../../std/thread/struct.JoinHandle.html
1080 /// [`thread::current`]: ../../std/thread/fn.current.html
1081 /// [`spawn`]: ../../std/thread/fn.spawn.html
1088 // Used only internally to construct a thread object without spawning
1089 // Panics if the name contains nuls.
1090 pub(crate) fn new(name: Option<String>) -> Thread {
1091 let cname = name.map(|n| {
1092 CString::new(n).expect("thread name may not contain interior null bytes")
1095 inner: Arc::new(Inner {
1097 id: ThreadId::new(),
1098 state: AtomicUsize::new(EMPTY),
1099 lock: Mutex::new(()),
1100 cvar: Condvar::new(),
1105 /// Atomically makes the handle's token available if it is not already.
1107 /// Every thread is equipped with some basic low-level blocking support, via
1108 /// the [`park`][park] function and the `unpark()` method. These can be
1109 /// used as a more CPU-efficient implementation of a spinlock.
1111 /// See the [park documentation][park] for more details.
1116 /// use std::thread;
1117 /// use std::time::Duration;
1119 /// let parked_thread = thread::Builder::new()
1121 /// println!("Parking thread");
1123 /// println!("Thread unparked");
1127 /// // Let some time pass for the thread to be spawned.
1128 /// thread::sleep(Duration::from_millis(10));
1130 /// println!("Unpark the thread");
1131 /// parked_thread.thread().unpark();
1133 /// parked_thread.join().unwrap();
1136 /// [park]: fn.park.html
1137 #[stable(feature = "rust1", since = "1.0.0")]
1138 pub fn unpark(&self) {
1139 // To ensure the unparked thread will observe any writes we made
1140 // before this call, we must perform a release operation that `park`
1141 // can synchronize with. To do that we must write `NOTIFIED` even if
1142 // `state` is already `NOTIFIED`. That is why this must be a swap
1143 // rather than a compare-and-swap that returns if it reads `NOTIFIED`
1145 match self.inner.state.swap(NOTIFIED, SeqCst) {
1146 EMPTY => return, // no one was waiting
1147 NOTIFIED => return, // already unparked
1148 PARKED => {} // gotta go wake someone up
1149 _ => panic!("inconsistent state in unpark"),
1152 // Coordinate wakeup through the mutex and a condvar notification
1153 let _lock = self.inner.lock.lock().unwrap();
1154 self.inner.cvar.notify_one()
1157 /// Gets the thread's unique identifier.
1162 /// use std::thread;
1164 /// let other_thread = thread::spawn(|| {
1165 /// thread::current().id()
1168 /// let other_thread_id = other_thread.join().unwrap();
1169 /// assert!(thread::current().id() != other_thread_id);
1171 #[stable(feature = "thread_id", since = "1.19.0")]
1172 pub fn id(&self) -> ThreadId {
1176 /// Gets the thread's name.
1178 /// For more information about named threads, see
1179 /// [this module-level documentation][naming-threads].
1183 /// Threads by default have no name specified:
1186 /// use std::thread;
1188 /// let builder = thread::Builder::new();
1190 /// let handler = builder.spawn(|| {
1191 /// assert!(thread::current().name().is_none());
1194 /// handler.join().unwrap();
1197 /// Thread with a specified name:
1200 /// use std::thread;
1202 /// let builder = thread::Builder::new()
1203 /// .name("foo".into());
1205 /// let handler = builder.spawn(|| {
1206 /// assert_eq!(thread::current().name(), Some("foo"))
1209 /// handler.join().unwrap();
1212 /// [naming-threads]: ./index.html#naming-threads
1213 #[stable(feature = "rust1", since = "1.0.0")]
1214 pub fn name(&self) -> Option<&str> {
1215 self.cname().map(|s| unsafe { str::from_utf8_unchecked(s.to_bytes()) } )
1218 fn cname(&self) -> Option<&CStr> {
1219 self.inner.name.as_ref().map(|s| &**s)
1223 #[stable(feature = "rust1", since = "1.0.0")]
1224 impl fmt::Debug for Thread {
1225 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1226 fmt::Debug::fmt(&self.name(), f)
1230 ////////////////////////////////////////////////////////////////////////////////
1232 ////////////////////////////////////////////////////////////////////////////////
1234 /// A specialized [`Result`] type for threads.
1236 /// Indicates the manner in which a thread exited.
1238 /// A thread that completes without panicking is considered to exit successfully.
1243 /// use std::thread;
1246 /// fn copy_in_thread() -> thread::Result<()> {
1247 /// thread::spawn(move || { fs::copy("foo.txt", "bar.txt").unwrap(); }).join()
1251 /// match copy_in_thread() {
1252 /// Ok(_) => println!("this is fine"),
1253 /// Err(_) => println!("thread panicked"),
1258 /// [`Result`]: ../../std/result/enum.Result.html
1259 #[stable(feature = "rust1", since = "1.0.0")]
1260 pub type Result<T> = ::result::Result<T, Box<dyn Any + Send + 'static>>;
1262 // This packet is used to communicate the return value between the child thread
1263 // and the parent thread. Memory is shared through the `Arc` within and there's
1264 // no need for a mutex here because synchronization happens with `join()` (the
1265 // parent thread never reads this packet until the child has exited).
1267 // This packet itself is then stored into a `JoinInner` which in turns is placed
1268 // in `JoinHandle` and `JoinGuard`. Due to the usage of `UnsafeCell` we need to
1269 // manually worry about impls like Send and Sync. The type `T` should
1270 // already always be Send (otherwise the thread could not have been created) and
1271 // this type is inherently Sync because no methods take &self. Regardless,
1272 // however, we add inheriting impls for Send/Sync to this type to ensure it's
1273 // Send/Sync and that future modifications will still appropriately classify it.
1274 struct Packet<T>(Arc<UnsafeCell<Option<Result<T>>>>);
1276 unsafe impl<T: Send> Send for Packet<T> {}
1277 unsafe impl<T: Sync> Sync for Packet<T> {}
1279 /// Inner representation for JoinHandle
1280 struct JoinInner<T> {
1281 native: Option<imp::Thread>,
1286 impl<T> JoinInner<T> {
1287 fn join(&mut self) -> Result<T> {
1288 self.native.take().unwrap().join();
1290 (*self.packet.0.get()).take().unwrap()
1295 /// An owned permission to join on a thread (block on its termination).
1297 /// A `JoinHandle` *detaches* the associated thread when it is dropped, which
1298 /// means that there is no longer any handle to thread and no way to `join`
1301 /// Due to platform restrictions, it is not possible to [`Clone`] this
1302 /// handle: the ability to join a thread is a uniquely-owned permission.
1304 /// This `struct` is created by the [`thread::spawn`] function and the
1305 /// [`thread::Builder::spawn`] method.
1309 /// Creation from [`thread::spawn`]:
1312 /// use std::thread;
1314 /// let join_handle: thread::JoinHandle<_> = thread::spawn(|| {
1315 /// // some work here
1319 /// Creation from [`thread::Builder::spawn`]:
1322 /// use std::thread;
1324 /// let builder = thread::Builder::new();
1326 /// let join_handle: thread::JoinHandle<_> = builder.spawn(|| {
1327 /// // some work here
1331 /// Child being detached and outliving its parent:
1334 /// use std::thread;
1335 /// use std::time::Duration;
1337 /// let original_thread = thread::spawn(|| {
1338 /// let _detached_thread = thread::spawn(|| {
1339 /// // Here we sleep to make sure that the first thread returns before.
1340 /// thread::sleep(Duration::from_millis(10));
1341 /// // This will be called, even though the JoinHandle is dropped.
1342 /// println!("♫ Still alive ♫");
1346 /// original_thread.join().expect("The thread being joined has panicked");
1347 /// println!("Original thread is joined.");
1349 /// // We make sure that the new thread has time to run, before the main
1350 /// // thread returns.
1352 /// thread::sleep(Duration::from_millis(1000));
1355 /// [`Clone`]: ../../std/clone/trait.Clone.html
1356 /// [`thread::spawn`]: fn.spawn.html
1357 /// [`thread::Builder::spawn`]: struct.Builder.html#method.spawn
1358 #[stable(feature = "rust1", since = "1.0.0")]
1359 pub struct JoinHandle<T>(JoinInner<T>);
1361 #[stable(feature = "joinhandle_impl_send_sync", since = "1.29.0")]
1362 unsafe impl<T> Send for JoinHandle<T> {}
1363 #[stable(feature = "joinhandle_impl_send_sync", since = "1.29.0")]
1364 unsafe impl<T> Sync for JoinHandle<T> {}
1366 impl<T> JoinHandle<T> {
1367 /// Extracts a handle to the underlying thread.
1372 /// use std::thread;
1374 /// let builder = thread::Builder::new();
1376 /// let join_handle: thread::JoinHandle<_> = builder.spawn(|| {
1377 /// // some work here
1380 /// let thread = join_handle.thread();
1381 /// println!("thread id: {:?}", thread.id());
1383 #[stable(feature = "rust1", since = "1.0.0")]
1384 pub fn thread(&self) -> &Thread {
1388 /// Waits for the associated thread to finish.
1390 /// In terms of [atomic memory orderings], the completion of the associated
1391 /// thread synchronizes with this function returning. In other words, all
1392 /// operations performed by that thread are ordered before all
1393 /// operations that happen after `join` returns.
1395 /// If the child thread panics, [`Err`] is returned with the parameter given
1398 /// [`Err`]: ../../std/result/enum.Result.html#variant.Err
1399 /// [`panic`]: ../../std/macro.panic.html
1400 /// [atomic memory orderings]: ../../std/sync/atomic/index.html
1404 /// This function may panic on some platforms if a thread attempts to join
1405 /// itself or otherwise may create a deadlock with joining threads.
1410 /// use std::thread;
1412 /// let builder = thread::Builder::new();
1414 /// let join_handle: thread::JoinHandle<_> = builder.spawn(|| {
1415 /// // some work here
1417 /// join_handle.join().expect("Couldn't join on the associated thread");
1419 #[stable(feature = "rust1", since = "1.0.0")]
1420 pub fn join(mut self) -> Result<T> {
1425 impl<T> AsInner<imp::Thread> for JoinHandle<T> {
1426 fn as_inner(&self) -> &imp::Thread { self.0.native.as_ref().unwrap() }
1429 impl<T> IntoInner<imp::Thread> for JoinHandle<T> {
1430 fn into_inner(self) -> imp::Thread { self.0.native.unwrap() }
1433 #[stable(feature = "std_debug", since = "1.16.0")]
1434 impl<T> fmt::Debug for JoinHandle<T> {
1435 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1436 f.pad("JoinHandle { .. }")
1440 fn _assert_sync_and_send() {
1441 fn _assert_both<T: Send + Sync>() {}
1442 _assert_both::<JoinHandle<()>>();
1443 _assert_both::<Thread>();
1446 ////////////////////////////////////////////////////////////////////////////////
1448 ////////////////////////////////////////////////////////////////////////////////
1450 #[cfg(all(test, not(target_os = "emscripten")))]
1453 use sync::mpsc::{channel, Sender};
1455 use super::{Builder};
1460 // !!! These tests are dangerous. If something is buggy, they will hang, !!!
1461 // !!! instead of exiting cleanly. This might wedge the buildbots. !!!
1464 fn test_unnamed_thread() {
1465 thread::spawn(move|| {
1466 assert!(thread::current().name().is_none());
1467 }).join().ok().unwrap();
1471 fn test_named_thread() {
1472 Builder::new().name("ada lovelace".to_string()).spawn(move|| {
1473 assert!(thread::current().name().unwrap() == "ada lovelace".to_string());
1474 }).unwrap().join().unwrap();
1479 fn test_invalid_named_thread() {
1480 let _ = Builder::new().name("ada l\0velace".to_string()).spawn(|| {});
1484 fn test_run_basic() {
1485 let (tx, rx) = channel();
1486 thread::spawn(move|| {
1487 tx.send(()).unwrap();
1493 fn test_join_panic() {
1494 match thread::spawn(move|| {
1497 result::Result::Err(_) => (),
1498 result::Result::Ok(()) => panic!()
1503 fn test_spawn_sched() {
1504 let (tx, rx) = channel();
1506 fn f(i: i32, tx: Sender<()>) {
1507 let tx = tx.clone();
1508 thread::spawn(move|| {
1510 tx.send(()).unwrap();
1522 fn test_spawn_sched_childs_on_default_sched() {
1523 let (tx, rx) = channel();
1525 thread::spawn(move|| {
1526 thread::spawn(move|| {
1527 tx.send(()).unwrap();
1534 fn avoid_copying_the_body<F>(spawnfn: F) where F: FnOnce(Box<dyn Fn() + Send>) {
1535 let (tx, rx) = channel();
1537 let x: Box<_> = box 1;
1538 let x_in_parent = (&*x) as *const i32 as usize;
1540 spawnfn(Box::new(move|| {
1541 let x_in_child = (&*x) as *const i32 as usize;
1542 tx.send(x_in_child).unwrap();
1545 let x_in_child = rx.recv().unwrap();
1546 assert_eq!(x_in_parent, x_in_child);
1550 fn test_avoid_copying_the_body_spawn() {
1551 avoid_copying_the_body(|v| {
1552 thread::spawn(move || v());
1557 fn test_avoid_copying_the_body_thread_spawn() {
1558 avoid_copying_the_body(|f| {
1559 thread::spawn(move|| {
1566 fn test_avoid_copying_the_body_join() {
1567 avoid_copying_the_body(|f| {
1568 let _ = thread::spawn(move|| {
1575 fn test_child_doesnt_ref_parent() {
1576 // If the child refcounts the parent thread, this will stack overflow when
1577 // climbing the thread tree to dereference each ancestor. (See #1789)
1578 // (well, it would if the constant were 8000+ - I lowered it to be more
1579 // valgrind-friendly. try this at home, instead..!)
1580 const GENERATIONS: u32 = 16;
1581 fn child_no(x: u32) -> Box<dyn Fn() + Send> {
1582 return Box::new(move|| {
1583 if x < GENERATIONS {
1584 thread::spawn(move|| child_no(x+1)());
1588 thread::spawn(|| child_no(0)());
1592 fn test_simple_newsched_spawn() {
1593 thread::spawn(move || {});
1597 fn test_try_panic_message_static_str() {
1598 match thread::spawn(move|| {
1599 panic!("static string");
1602 type T = &'static str;
1603 assert!(e.is::<T>());
1604 assert_eq!(*e.downcast::<T>().unwrap(), "static string");
1611 fn test_try_panic_message_owned_str() {
1612 match thread::spawn(move|| {
1613 panic!("owned string".to_string());
1617 assert!(e.is::<T>());
1618 assert_eq!(*e.downcast::<T>().unwrap(), "owned string".to_string());
1625 fn test_try_panic_message_any() {
1626 match thread::spawn(move|| {
1627 panic!(box 413u16 as Box<dyn Any + Send>);
1630 type T = Box<dyn Any + Send>;
1631 assert!(e.is::<T>());
1632 let any = e.downcast::<T>().unwrap();
1633 assert!(any.is::<u16>());
1634 assert_eq!(*any.downcast::<u16>().unwrap(), 413);
1641 fn test_try_panic_message_unit_struct() {
1644 match thread::spawn(move|| {
1647 Err(ref e) if e.is::<Juju>() => {}
1648 Err(_) | Ok(()) => panic!()
1653 fn test_park_timeout_unpark_before() {
1655 thread::current().unpark();
1656 thread::park_timeout(Duration::from_millis(u32::MAX as u64));
1661 fn test_park_timeout_unpark_not_called() {
1663 thread::park_timeout(Duration::from_millis(10));
1668 fn test_park_timeout_unpark_called_other_thread() {
1670 let th = thread::current();
1672 let _guard = thread::spawn(move || {
1673 super::sleep(Duration::from_millis(50));
1677 thread::park_timeout(Duration::from_millis(u32::MAX as u64));
1682 fn sleep_ms_smoke() {
1683 thread::sleep(Duration::from_millis(2));
1687 fn test_thread_id_equal() {
1688 assert!(thread::current().id() == thread::current().id());
1692 fn test_thread_id_not_equal() {
1693 let spawned_id = thread::spawn(|| thread::current().id()).join().unwrap();
1694 assert!(thread::current().id() != spawned_id);
1697 // NOTE: the corresponding test for stderr is in run-pass/thread-stderr, due
1698 // to the test harness apparently interfering with stderr configuration.