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. Thread panic is unrecoverable from within
29 //! the panicking thread (i.e. there is no 'try/catch' in Rust), but
30 //! the panic may optionally be detected from a different thread. If
31 //! the main thread panics, the application will exit with a non-zero
34 //! When the main thread of a Rust program terminates, the entire program shuts
35 //! down, even if other threads are still running. However, this module provides
36 //! convenient facilities for automatically waiting for the termination of a
37 //! child thread (i.e., join).
39 //! ## Spawning a thread
41 //! A new thread can be spawned using the [`thread::spawn`][`spawn`] function:
46 //! thread::spawn(move || {
51 //! In this example, the spawned thread is "detached" from the current
52 //! thread. This means that it can outlive its parent (the thread that spawned
53 //! it), unless this parent is the main thread.
55 //! The parent thread can also wait on the completion of the child
56 //! thread; a call to [`spawn`] produces a [`JoinHandle`], which provides
57 //! a `join` method for waiting:
62 //! let child = thread::spawn(move || {
66 //! let res = child.join();
69 //! The [`join`] method returns a [`thread::Result`] containing [`Ok`] of the final
70 //! value produced by the child thread, or [`Err`] of the value given to
71 //! a call to [`panic!`] if the child panicked.
73 //! ## Configuring threads
75 //! A new thread can be configured before it is spawned via the [`Builder`] type,
76 //! which currently allows you to set the name and stack size for the child thread:
79 //! # #![allow(unused_must_use)]
82 //! thread::Builder::new().name("child1".to_string()).spawn(move || {
83 //! println!("Hello, world!");
87 //! ## The `Thread` type
89 //! Threads are represented via the [`Thread`] type, which you can get in one of
92 //! * By spawning a new thread, e.g. using the [`thread::spawn`][`spawn`]
93 //! function, and calling [`thread`][`JoinHandle::thread`] on the [`JoinHandle`].
94 //! * By requesting the current thread, using the [`thread::current`] function.
96 //! The [`thread::current`] function is available even for threads not spawned
97 //! by the APIs of this module.
99 //! ## Thread-local storage
101 //! This module also provides an implementation of thread-local storage for Rust
102 //! programs. Thread-local storage is a method of storing data into a global
103 //! variable that each thread in the program will have its own copy of.
104 //! Threads do not share this data, so accesses do not need to be synchronized.
106 //! A thread-local key owns the value it contains and will destroy the value when the
107 //! thread exits. It is created with the [`thread_local!`] macro and can contain any
108 //! value that is `'static` (no borrowed pointers). It provides an accessor function,
109 //! [`with`], that yields a shared reference to the value to the specified
110 //! closure. Thread-local keys allow only shared access to values, as there would be no
111 //! way to guarantee uniqueness if mutable borrows were allowed. Most values
112 //! will want to make use of some form of **interior mutability** through the
113 //! [`Cell`] or [`RefCell`] types.
115 //! [channels]: ../../std/sync/mpsc/index.html
116 //! [`Arc`]: ../../std/sync/struct.Arc.html
117 //! [`spawn`]: ../../std/thread/fn.spawn.html
118 //! [`JoinHandle`]: ../../std/thread/struct.JoinHandle.html
119 //! [`JoinHandle::thread`]: ../../std/thread/struct.JoinHandle.html#method.thread
120 //! [`join`]: ../../std/thread/struct.JoinHandle.html#method.join
121 //! [`Result`]: ../../std/result/enum.Result.html
122 //! [`Ok`]: ../../std/result/enum.Result.html#variant.Ok
123 //! [`Err`]: ../../std/result/enum.Result.html#variant.Err
124 //! [`panic!`]: ../../std/macro.panic.html
125 //! [`Builder`]: ../../std/thread/struct.Builder.html
126 //! [`thread::current`]: ../../std/thread/fn.current.html
127 //! [`thread::Result`]: ../../std/thread/type.Result.html
128 //! [`Thread`]: ../../std/thread/struct.Thread.html
129 //! [`park`]: ../../std/thread/fn.park.html
130 //! [`unpark`]: ../../std/thread/struct.Thread.html#method.unpark
131 //! [`thread::park_timeout`]: ../../std/thread/fn.park_timeout.html
132 //! [`Cell`]: ../cell/struct.Cell.html
133 //! [`RefCell`]: ../cell/struct.RefCell.html
134 //! [`thread_local!`]: ../macro.thread_local.html
135 //! [`with`]: struct.LocalKey.html#method.with
137 #![stable(feature = "rust1", since = "1.0.0")]
140 use cell::UnsafeCell;
141 use ffi::{CStr, CString};
147 use sync::{Mutex, Condvar, Arc};
148 use sys::thread as imp;
149 use sys_common::mutex;
150 use sys_common::thread_info;
151 use sys_common::util;
152 use sys_common::{AsInner, IntoInner};
155 ////////////////////////////////////////////////////////////////////////////////
156 // Thread-local storage
157 ////////////////////////////////////////////////////////////////////////////////
159 #[macro_use] mod local;
161 #[stable(feature = "rust1", since = "1.0.0")]
162 pub use self::local::{LocalKey, LocalKeyState};
164 // The types used by the thread_local! macro to access TLS keys. Note that there
165 // are two types, the "OS" type and the "fast" type. The OS thread local key
166 // type is accessed via platform-specific API calls and is slow, while the fast
167 // key type is accessed via code generated via LLVM, where TLS keys are set up
168 // by the elf linker. Note that the OS TLS type is always available: on macOS
169 // the standard library is compiled with support for older platform versions
170 // where fast TLS was not available; end-user code is compiled with fast TLS
171 // where available, but both are needed.
173 #[unstable(feature = "libstd_thread_internals", issue = "0")]
174 #[cfg(target_thread_local)]
175 #[doc(hidden)] pub use sys::fast_thread_local::Key as __FastLocalKeyInner;
176 #[unstable(feature = "libstd_thread_internals", issue = "0")]
177 #[doc(hidden)] pub use self::local::os::Key as __OsLocalKeyInner;
179 ////////////////////////////////////////////////////////////////////////////////
181 ////////////////////////////////////////////////////////////////////////////////
183 /// Thread configuration. Provides detailed control over the properties
184 /// and behavior of new threads.
191 /// let builder = thread::Builder::new();
193 /// let handler = builder.spawn(|| {
197 /// handler.join().unwrap();
199 #[stable(feature = "rust1", since = "1.0.0")]
202 // A name for the thread-to-be, for identification in panic messages
203 name: Option<String>,
204 // The size of the stack for the spawned thread in bytes
205 stack_size: Option<usize>,
209 /// Generates the base configuration for spawning a thread, from which
210 /// configuration methods can be chained.
212 /// If the [`stack_size`] field is not specified, the stack size
213 /// will be the `RUST_MIN_STACK` environment variable, if it is
214 /// not specified either, a sensible default size will be set (2MB as
215 /// of the writting of this doc).
222 /// let builder = thread::Builder::new()
223 /// .name("foo".into())
226 /// let handler = builder.spawn(|| {
230 /// handler.join().unwrap();
233 /// [`stack_size`]: ../../std/thread/struct.Builder.html#method.stack_size
234 #[stable(feature = "rust1", since = "1.0.0")]
235 pub fn new() -> Builder {
242 /// Names the thread-to-be. Currently the name is used for identification
243 /// only in panic messages.
250 /// let builder = thread::Builder::new()
251 /// .name("foo".into());
253 /// let handler = builder.spawn(|| {
254 /// assert_eq!(thread::current().name(), Some("foo"))
257 /// handler.join().unwrap();
259 #[stable(feature = "rust1", since = "1.0.0")]
260 pub fn name(mut self, name: String) -> Builder {
261 self.name = Some(name);
265 /// Sets the size of the stack (in bytes) for the new thread.
267 /// The actual stack size may be greater than this value if
268 /// the platform specifies minimal stack size.
275 /// let builder = thread::Builder::new().stack_size(32 * 1024);
277 #[stable(feature = "rust1", since = "1.0.0")]
278 pub fn stack_size(mut self, size: usize) -> Builder {
279 self.stack_size = Some(size);
283 /// Spawns a new thread, and returns a join handle for it.
285 /// The child thread may outlive the parent (unless the parent thread
286 /// is the main thread; the whole process is terminated when the main
287 /// thread finishes). The join handle can be used to block on
288 /// termination of the child thread, including recovering its panics.
290 /// For a more complete documentation see [`thread::spawn`][`spawn`].
294 /// Unlike the [`spawn`] free function, this method yields an
295 /// [`io::Result`] to capture any failure to create the thread at
298 /// [`spawn`]: ../../std/thread/fn.spawn.html
299 /// [`io::Result`]: ../../std/io/type.Result.html
306 /// let builder = thread::Builder::new();
308 /// let handler = builder.spawn(|| {
312 /// handler.join().unwrap();
314 #[stable(feature = "rust1", since = "1.0.0")]
315 pub fn spawn<F, T>(self, f: F) -> io::Result<JoinHandle<T>> where
316 F: FnOnce() -> T, F: Send + 'static, T: Send + 'static
318 let Builder { name, stack_size } = self;
320 let stack_size = stack_size.unwrap_or(util::min_stack());
322 let my_thread = Thread::new(name);
323 let their_thread = my_thread.clone();
325 let my_packet : Arc<UnsafeCell<Option<Result<T>>>>
326 = Arc::new(UnsafeCell::new(None));
327 let their_packet = my_packet.clone();
330 if let Some(name) = their_thread.cname() {
331 imp::Thread::set_name(name);
334 thread_info::set(imp::guard::current(), their_thread);
335 let try_result = panic::catch_unwind(panic::AssertUnwindSafe(|| {
336 ::sys_common::backtrace::__rust_begin_short_backtrace(f)
338 *their_packet.get() = Some(try_result);
342 Ok(JoinHandle(JoinInner {
344 Some(imp::Thread::new(stack_size, Box::new(main))?)
347 packet: Packet(my_packet),
352 ////////////////////////////////////////////////////////////////////////////////
354 ////////////////////////////////////////////////////////////////////////////////
356 /// Spawns a new thread, returning a [`JoinHandle`] for it.
358 /// The join handle will implicitly *detach* the child thread upon being
359 /// dropped. In this case, the child thread may outlive the parent (unless
360 /// the parent thread is the main thread; the whole process is terminated when
361 /// the main thread finishes). Additionally, the join handle provides a [`join`]
362 /// method that can be used to join the child thread. If the child thread
363 /// panics, [`join`] will return an [`Err`] containing the argument given to
366 /// This will create a thread using default parameters of [`Builder`], if you
367 /// want to specify the stack size or the name of the thread, use this API
372 /// Panics if the OS fails to create a thread; use [`Builder::spawn`]
373 /// to recover from such errors.
377 /// Creating a thread.
382 /// let handler = thread::spawn(|| {
386 /// handler.join().unwrap();
389 /// As mentioned in the module documentation, threads are usually made to
390 /// communicate using [`channels`], here is how it usually looks.
392 /// This example also shows how to use `move`, in order to give ownership
393 /// of values to a thread.
397 /// use std::sync::mpsc::channel;
399 /// let (tx, rx) = channel();
401 /// let sender = thread::spawn(move || {
402 /// let _ = tx.send("Hello, thread".to_owned());
405 /// let receiver = thread::spawn(move || {
406 /// println!("{}", rx.recv().unwrap());
409 /// let _ = sender.join();
410 /// let _ = receiver.join();
413 /// A thread can also return a value through its [`JoinHandle`], you can use
414 /// this to make asynchronous computations (futures might be more appropriate
420 /// let computation = thread::spawn(|| {
421 /// // Some expensive computation.
425 /// let result = computation.join().unwrap();
426 /// println!("{}", result);
429 /// [`channels`]: ../../std/sync/mpsc/index.html
430 /// [`JoinHandle`]: ../../std/thread/struct.JoinHandle.html
431 /// [`join`]: ../../std/thread/struct.JoinHandle.html#method.join
432 /// [`Err`]: ../../std/result/enum.Result.html#variant.Err
433 /// [`panic`]: ../../std/macro.panic.html
434 /// [`Builder::spawn`]: ../../std/thread/struct.Builder.html#method.spawn
435 /// [`Builder`]: ../../std/thread/struct.Builder.html
436 #[stable(feature = "rust1", since = "1.0.0")]
437 pub fn spawn<F, T>(f: F) -> JoinHandle<T> where
438 F: FnOnce() -> T, F: Send + 'static, T: Send + 'static
440 Builder::new().spawn(f).unwrap()
443 /// Gets a handle to the thread that invokes it.
447 /// Getting a handle to the current thread with `thread::current()`:
452 /// let handler = thread::Builder::new()
453 /// .name("named thread".into())
455 /// let handle = thread::current();
456 /// assert_eq!(handle.name(), Some("named thread"));
460 /// handler.join().unwrap();
462 #[stable(feature = "rust1", since = "1.0.0")]
463 pub fn current() -> Thread {
464 thread_info::current_thread().expect("use of std::thread::current() is not \
465 possible after the thread's local \
466 data has been destroyed")
469 /// Cooperatively gives up a timeslice to the OS scheduler.
476 /// thread::yield_now();
478 #[stable(feature = "rust1", since = "1.0.0")]
480 imp::Thread::yield_now()
483 /// Determines whether the current thread is unwinding because of panic.
485 /// A common use of this feature is to poison shared resources when writing
486 /// unsafe code, by checking `panicking` when the `drop` is called.
488 /// This is usually not needed when writing safe code, as [`Mutex`es][Mutex]
489 /// already poison themselves when a thread panics while holding the lock.
491 /// This can also be used in multithreaded applications, in order to send a
492 /// message to other threads warning that a thread has panicked (e.g. for
493 /// monitoring purposes).
500 /// struct SomeStruct;
502 /// impl Drop for SomeStruct {
503 /// fn drop(&mut self) {
504 /// if thread::panicking() {
505 /// println!("dropped while unwinding");
507 /// println!("dropped while not unwinding");
514 /// let a = SomeStruct;
519 /// let b = SomeStruct;
524 /// [Mutex]: ../../std/sync/struct.Mutex.html
526 #[stable(feature = "rust1", since = "1.0.0")]
527 pub fn panicking() -> bool {
528 panicking::panicking()
531 /// Puts the current thread to sleep for the specified amount of time.
533 /// The thread may sleep longer than the duration specified due to scheduling
534 /// specifics or platform-dependent functionality.
536 /// # Platform behavior
538 /// On Unix platforms this function will not return early due to a
539 /// signal being received or a spurious wakeup.
546 /// // Let's sleep for 2 seconds:
547 /// thread::sleep_ms(2000);
549 #[stable(feature = "rust1", since = "1.0.0")]
550 #[rustc_deprecated(since = "1.6.0", reason = "replaced by `std::thread::sleep`")]
551 pub fn sleep_ms(ms: u32) {
552 sleep(Duration::from_millis(ms as u64))
555 /// Puts the current thread to sleep for the specified amount of time.
557 /// The thread may sleep longer than the duration specified due to scheduling
558 /// specifics or platform-dependent functionality.
560 /// # Platform behavior
562 /// On Unix platforms this function will not return early due to a
563 /// signal being received or a spurious wakeup. Platforms which do not support
564 /// nanosecond precision for sleeping will have `dur` rounded up to the nearest
565 /// granularity of time they can sleep for.
570 /// use std::{thread, time};
572 /// let ten_millis = time::Duration::from_millis(10);
573 /// let now = time::Instant::now();
575 /// thread::sleep(ten_millis);
577 /// assert!(now.elapsed() >= ten_millis);
579 #[stable(feature = "thread_sleep", since = "1.4.0")]
580 pub fn sleep(dur: Duration) {
581 imp::Thread::sleep(dur)
584 /// Blocks unless or until the current thread's token is made available.
586 /// A call to `park` does not guarantee that the thread will remain parked
587 /// forever, and callers should be prepared for this possibility.
589 /// # park and unpark
591 /// Every thread is equipped with some basic low-level blocking support, via the
592 /// [`thread::park`][`park`] function and [`thread::Thread::unpark`][`unpark`]
593 /// method. [`park`] blocks the current thread, which can then be resumed from
594 /// another thread by calling the [`unpark`] method on the blocked thread's
597 /// Conceptually, each [`Thread`] handle has an associated token, which is
598 /// initially not present:
600 /// * The [`thread::park`][`park`] function blocks the current thread unless or
601 /// until the token is available for its thread handle, at which point it
602 /// atomically consumes the token. It may also return *spuriously*, without
603 /// consuming the token. [`thread::park_timeout`] does the same, but allows
604 /// specifying a maximum time to block the thread for.
606 /// * The [`unpark`] method on a [`Thread`] atomically makes the token available
607 /// if it wasn't already.
609 /// In other words, each [`Thread`] acts a bit like a spinlock that can be
610 /// locked and unlocked using `park` and `unpark`.
612 /// The API is typically used by acquiring a handle to the current thread,
613 /// placing that handle in a shared data structure so that other threads can
614 /// find it, and then `park`ing. When some desired condition is met, another
615 /// thread calls [`unpark`] on the handle.
617 /// The motivation for this design is twofold:
619 /// * It avoids the need to allocate mutexes and condvars when building new
620 /// synchronization primitives; the threads already provide basic
621 /// blocking/signaling.
623 /// * It can be implemented very efficiently on many platforms.
629 /// use std::time::Duration;
631 /// let parked_thread = thread::Builder::new()
633 /// println!("Parking thread");
635 /// println!("Thread unparked");
639 /// // Let some time pass for the thread to be spawned.
640 /// thread::sleep(Duration::from_millis(10));
642 /// println!("Unpark the thread");
643 /// parked_thread.thread().unpark();
645 /// parked_thread.join().unwrap();
648 /// [`Thread`]: ../../std/thread/struct.Thread.html
649 /// [`park`]: ../../std/thread/fn.park.html
650 /// [`unpark`]: ../../std/thread/struct.Thread.html#method.unpark
651 /// [`thread::park_timeout`]: ../../std/thread/fn.park_timeout.html
653 // The implementation currently uses the trivial strategy of a Mutex+Condvar
654 // with wakeup flag, which does not actually allow spurious wakeups. In the
655 // future, this will be implemented in a more efficient way, perhaps along the lines of
656 // http://cr.openjdk.java.net/~stefank/6989984.1/raw_files/new/src/os/linux/vm/os_linux.cpp
657 // or futuxes, and in either case may allow spurious wakeups.
658 #[stable(feature = "rust1", since = "1.0.0")]
660 let thread = current();
661 let mut guard = thread.inner.lock.lock().unwrap();
663 guard = thread.inner.cvar.wait(guard).unwrap();
668 /// Use [`park_timeout`].
670 /// Blocks unless or until the current thread's token is made available or
671 /// the specified duration has been reached (may wake spuriously).
673 /// The semantics of this function are equivalent to [`park`] except
674 /// that the thread will be blocked for roughly no longer than `dur`. This
675 /// method should not be used for precise timing due to anomalies such as
676 /// preemption or platform differences that may not cause the maximum
677 /// amount of time waited to be precisely `ms` long.
679 /// See the [park documentation][`park`] for more detail.
681 /// [`park_timeout`]: fn.park_timeout.html
682 /// [`park`]: ../../std/thread/fn.park.html
683 #[stable(feature = "rust1", since = "1.0.0")]
684 #[rustc_deprecated(since = "1.6.0", reason = "replaced by `std::thread::park_timeout`")]
685 pub fn park_timeout_ms(ms: u32) {
686 park_timeout(Duration::from_millis(ms as u64))
689 /// Blocks unless or until the current thread's token is made available or
690 /// the specified duration has been reached (may wake spuriously).
692 /// The semantics of this function are equivalent to [`park`][park] except
693 /// that the thread will be blocked for roughly no longer than `dur`. This
694 /// method should not be used for precise timing due to anomalies such as
695 /// preemption or platform differences that may not cause the maximum
696 /// amount of time waited to be precisely `dur` long.
698 /// See the [park dococumentation][park] for more details.
700 /// # Platform behavior
702 /// Platforms which do not support nanosecond precision for sleeping will have
703 /// `dur` rounded up to the nearest granularity of time they can sleep for.
707 /// Waiting for the complete expiration of the timeout:
710 /// use std::thread::park_timeout;
711 /// use std::time::{Instant, Duration};
713 /// let timeout = Duration::from_secs(2);
714 /// let beginning_park = Instant::now();
715 /// park_timeout(timeout);
717 /// while beginning_park.elapsed() < timeout {
718 /// println!("restarting park_timeout after {:?}", beginning_park.elapsed());
719 /// let timeout = timeout - beginning_park.elapsed();
720 /// park_timeout(timeout);
724 /// [park]: fn.park.html
725 #[stable(feature = "park_timeout", since = "1.4.0")]
726 pub fn park_timeout(dur: Duration) {
727 let thread = current();
728 let mut guard = thread.inner.lock.lock().unwrap();
730 let (g, _) = thread.inner.cvar.wait_timeout(guard, dur).unwrap();
736 ////////////////////////////////////////////////////////////////////////////////
738 ////////////////////////////////////////////////////////////////////////////////
740 /// A unique identifier for a running thread.
742 /// A `ThreadId` is an opaque object that has a unique value for each thread
743 /// that creates one. `ThreadId`s are not guaranteed to correspond to a thread's
744 /// system-designated identifier.
749 /// #![feature(thread_id)]
753 /// let other_thread = thread::spawn(|| {
754 /// thread::current().id()
757 /// let other_thread_id = other_thread.join().unwrap();
758 /// assert!(thread::current().id() != other_thread_id);
760 #[unstable(feature = "thread_id", issue = "21507")]
761 #[derive(Eq, PartialEq, Clone, Copy, Hash, Debug)]
762 pub struct ThreadId(u64);
765 // Generate a new unique thread ID.
766 fn new() -> ThreadId {
767 static GUARD: mutex::Mutex = mutex::Mutex::new();
768 static mut COUNTER: u64 = 0;
773 // If we somehow use up all our bits, panic so that we're not
774 // covering up subtle bugs of IDs being reused.
775 if COUNTER == ::u64::MAX {
777 panic!("failed to generate unique thread ID: bitspace exhausted");
790 ////////////////////////////////////////////////////////////////////////////////
792 ////////////////////////////////////////////////////////////////////////////////
794 /// The internal representation of a `Thread` handle
796 name: Option<CString>, // Guaranteed to be UTF-8
798 lock: Mutex<bool>, // true when there is a buffered unpark
803 #[stable(feature = "rust1", since = "1.0.0")]
804 /// A handle to a thread.
806 /// Threads are represented via the `Thread` type, which you can get in one of
809 /// * By spawning a new thread, e.g. using the [`thread::spawn`][`spawn`]
810 /// function, and calling [`thread`][`JoinHandle::thread`] on the
812 /// * By requesting the current thread, using the [`thread::current`] function.
814 /// The [`thread::current`] function is available even for threads not spawned
815 /// by the APIs of this module.
817 /// There is usualy no need to create a `Thread` struct yourself, one
818 /// should instead use a function like `spawn` to create new threads, see the
819 /// docs of [`Builder`] and [`spawn`] for more details.
821 /// [`Builder`]: ../../std/thread/struct.Builder.html
822 /// [`spawn`]: ../../std/thread/fn.spawn.html
829 // Used only internally to construct a thread object without spawning
830 pub(crate) fn new(name: Option<String>) -> Thread {
831 let cname = name.map(|n| {
832 CString::new(n).expect("thread name may not contain interior null bytes")
835 inner: Arc::new(Inner {
838 lock: Mutex::new(false),
839 cvar: Condvar::new(),
844 /// Atomically makes the handle's token available if it is not already.
846 /// Every thread is equipped with some basic low-level blocking support, via
847 /// the [`park`][park] function and the `unpark()` method. These can be
848 /// used as a more CPU-efficient implementation of a spinlock.
850 /// See the [park documentation][park] for more details.
856 /// use std::time::Duration;
858 /// let parked_thread = thread::Builder::new()
860 /// println!("Parking thread");
862 /// println!("Thread unparked");
866 /// // Let some time pass for the thread to be spawned.
867 /// thread::sleep(Duration::from_millis(10));
869 /// println!("Unpark the thread");
870 /// parked_thread.thread().unpark();
872 /// parked_thread.join().unwrap();
875 /// [park]: fn.park.html
876 #[stable(feature = "rust1", since = "1.0.0")]
877 pub fn unpark(&self) {
878 let mut guard = self.inner.lock.lock().unwrap();
881 self.inner.cvar.notify_one();
885 /// Gets the thread's unique identifier.
890 /// #![feature(thread_id)]
894 /// let other_thread = thread::spawn(|| {
895 /// thread::current().id()
898 /// let other_thread_id = other_thread.join().unwrap();
899 /// assert!(thread::current().id() != other_thread_id);
901 #[unstable(feature = "thread_id", issue = "21507")]
902 pub fn id(&self) -> ThreadId {
906 /// Gets the thread's name.
910 /// Threads by default have no name specified:
915 /// let builder = thread::Builder::new();
917 /// let handler = builder.spawn(|| {
918 /// assert!(thread::current().name().is_none());
921 /// handler.join().unwrap();
924 /// Thread with a specified name:
929 /// let builder = thread::Builder::new()
930 /// .name("foo".into());
932 /// let handler = builder.spawn(|| {
933 /// assert_eq!(thread::current().name(), Some("foo"))
936 /// handler.join().unwrap();
938 #[stable(feature = "rust1", since = "1.0.0")]
939 pub fn name(&self) -> Option<&str> {
940 self.cname().map(|s| unsafe { str::from_utf8_unchecked(s.to_bytes()) } )
943 fn cname(&self) -> Option<&CStr> {
944 self.inner.name.as_ref().map(|s| &**s)
948 #[stable(feature = "rust1", since = "1.0.0")]
949 impl fmt::Debug for Thread {
950 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
951 fmt::Debug::fmt(&self.name(), f)
955 ////////////////////////////////////////////////////////////////////////////////
957 ////////////////////////////////////////////////////////////////////////////////
959 /// A specialized [`Result`] type for threads.
961 /// Indicates the manner in which a thread exited.
963 /// A thread that completes without panicking is considered to exit successfully.
971 /// fn copy_in_thread() -> thread::Result<()> {
972 /// thread::spawn(move || { fs::copy("foo.txt", "bar.txt").unwrap(); }).join()
976 /// match copy_in_thread() {
977 /// Ok(_) => println!("this is fine"),
978 /// Err(_) => println!("thread panicked"),
983 /// [`Result`]: ../../std/result/enum.Result.html
984 #[stable(feature = "rust1", since = "1.0.0")]
985 pub type Result<T> = ::result::Result<T, Box<Any + Send + 'static>>;
987 // This packet is used to communicate the return value between the child thread
988 // and the parent thread. Memory is shared through the `Arc` within and there's
989 // no need for a mutex here because synchronization happens with `join()` (the
990 // parent thread never reads this packet until the child has exited).
992 // This packet itself is then stored into a `JoinInner` which in turns is placed
993 // in `JoinHandle` and `JoinGuard`. Due to the usage of `UnsafeCell` we need to
994 // manually worry about impls like Send and Sync. The type `T` should
995 // already always be Send (otherwise the thread could not have been created) and
996 // this type is inherently Sync because no methods take &self. Regardless,
997 // however, we add inheriting impls for Send/Sync to this type to ensure it's
998 // Send/Sync and that future modifications will still appropriately classify it.
999 struct Packet<T>(Arc<UnsafeCell<Option<Result<T>>>>);
1001 unsafe impl<T: Send> Send for Packet<T> {}
1002 unsafe impl<T: Sync> Sync for Packet<T> {}
1004 /// Inner representation for JoinHandle
1005 struct JoinInner<T> {
1006 native: Option<imp::Thread>,
1011 impl<T> JoinInner<T> {
1012 fn join(&mut self) -> Result<T> {
1013 self.native.take().unwrap().join();
1015 (*self.packet.0.get()).take().unwrap()
1020 /// An owned permission to join on a thread (block on its termination).
1022 /// A `JoinHandle` *detaches* the child thread when it is dropped.
1024 /// Due to platform restrictions, it is not possible to [`Clone`] this
1025 /// handle: the ability to join a child thread is a uniquely-owned
1028 /// This `struct` is created by the [`thread::spawn`] function and the
1029 /// [`thread::Builder::spawn`] method.
1033 /// Creation from [`thread::spawn`]:
1036 /// use std::thread;
1038 /// let join_handle: thread::JoinHandle<_> = thread::spawn(|| {
1039 /// // some work here
1043 /// Creation from [`thread::Builder::spawn`]:
1046 /// use std::thread;
1048 /// let builder = thread::Builder::new();
1050 /// let join_handle: thread::JoinHandle<_> = builder.spawn(|| {
1051 /// // some work here
1055 /// [`Clone`]: ../../std/clone/trait.Clone.html
1056 /// [`thread::spawn`]: fn.spawn.html
1057 /// [`thread::Builder::spawn`]: struct.Builder.html#method.spawn
1058 #[stable(feature = "rust1", since = "1.0.0")]
1059 pub struct JoinHandle<T>(JoinInner<T>);
1061 impl<T> JoinHandle<T> {
1062 /// Extracts a handle to the underlying thread.
1067 /// #![feature(thread_id)]
1069 /// use std::thread;
1071 /// let builder = thread::Builder::new();
1073 /// let join_handle: thread::JoinHandle<_> = builder.spawn(|| {
1074 /// // some work here
1077 /// let thread = join_handle.thread();
1078 /// println!("thread id: {:?}", thread.id());
1080 #[stable(feature = "rust1", since = "1.0.0")]
1081 pub fn thread(&self) -> &Thread {
1085 /// Waits for the associated thread to finish.
1087 /// If the child thread panics, [`Err`] is returned with the parameter given
1090 /// [`Err`]: ../../std/result/enum.Result.html#variant.Err
1091 /// [`panic`]: ../../std/macro.panic.html
1096 /// use std::thread;
1098 /// let builder = thread::Builder::new();
1100 /// let join_handle: thread::JoinHandle<_> = builder.spawn(|| {
1101 /// // some work here
1103 /// join_handle.join().expect("Couldn't join on the associated thread");
1105 #[stable(feature = "rust1", since = "1.0.0")]
1106 pub fn join(mut self) -> Result<T> {
1111 impl<T> AsInner<imp::Thread> for JoinHandle<T> {
1112 fn as_inner(&self) -> &imp::Thread { self.0.native.as_ref().unwrap() }
1115 impl<T> IntoInner<imp::Thread> for JoinHandle<T> {
1116 fn into_inner(self) -> imp::Thread { self.0.native.unwrap() }
1119 #[stable(feature = "std_debug", since = "1.16.0")]
1120 impl<T> fmt::Debug for JoinHandle<T> {
1121 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1122 f.pad("JoinHandle { .. }")
1126 fn _assert_sync_and_send() {
1127 fn _assert_both<T: Send + Sync>() {}
1128 _assert_both::<JoinHandle<()>>();
1129 _assert_both::<Thread>();
1132 ////////////////////////////////////////////////////////////////////////////////
1134 ////////////////////////////////////////////////////////////////////////////////
1136 #[cfg(all(test, not(target_os = "emscripten")))]
1139 use sync::mpsc::{channel, Sender};
1141 use super::{Builder};
1146 // !!! These tests are dangerous. If something is buggy, they will hang, !!!
1147 // !!! instead of exiting cleanly. This might wedge the buildbots. !!!
1150 fn test_unnamed_thread() {
1151 thread::spawn(move|| {
1152 assert!(thread::current().name().is_none());
1153 }).join().ok().unwrap();
1157 fn test_named_thread() {
1158 Builder::new().name("ada lovelace".to_string()).spawn(move|| {
1159 assert!(thread::current().name().unwrap() == "ada lovelace".to_string());
1160 }).unwrap().join().unwrap();
1165 fn test_invalid_named_thread() {
1166 let _ = Builder::new().name("ada l\0velace".to_string()).spawn(|| {});
1170 fn test_run_basic() {
1171 let (tx, rx) = channel();
1172 thread::spawn(move|| {
1173 tx.send(()).unwrap();
1179 fn test_join_panic() {
1180 match thread::spawn(move|| {
1183 result::Result::Err(_) => (),
1184 result::Result::Ok(()) => panic!()
1189 fn test_spawn_sched() {
1190 let (tx, rx) = channel();
1192 fn f(i: i32, tx: Sender<()>) {
1193 let tx = tx.clone();
1194 thread::spawn(move|| {
1196 tx.send(()).unwrap();
1208 fn test_spawn_sched_childs_on_default_sched() {
1209 let (tx, rx) = channel();
1211 thread::spawn(move|| {
1212 thread::spawn(move|| {
1213 tx.send(()).unwrap();
1220 fn avoid_copying_the_body<F>(spawnfn: F) where F: FnOnce(Box<Fn() + Send>) {
1221 let (tx, rx) = channel();
1223 let x: Box<_> = box 1;
1224 let x_in_parent = (&*x) as *const i32 as usize;
1226 spawnfn(Box::new(move|| {
1227 let x_in_child = (&*x) as *const i32 as usize;
1228 tx.send(x_in_child).unwrap();
1231 let x_in_child = rx.recv().unwrap();
1232 assert_eq!(x_in_parent, x_in_child);
1236 fn test_avoid_copying_the_body_spawn() {
1237 avoid_copying_the_body(|v| {
1238 thread::spawn(move || v());
1243 fn test_avoid_copying_the_body_thread_spawn() {
1244 avoid_copying_the_body(|f| {
1245 thread::spawn(move|| {
1252 fn test_avoid_copying_the_body_join() {
1253 avoid_copying_the_body(|f| {
1254 let _ = thread::spawn(move|| {
1261 fn test_child_doesnt_ref_parent() {
1262 // If the child refcounts the parent thread, this will stack overflow when
1263 // climbing the thread tree to dereference each ancestor. (See #1789)
1264 // (well, it would if the constant were 8000+ - I lowered it to be more
1265 // valgrind-friendly. try this at home, instead..!)
1266 const GENERATIONS: u32 = 16;
1267 fn child_no(x: u32) -> Box<Fn() + Send> {
1268 return Box::new(move|| {
1269 if x < GENERATIONS {
1270 thread::spawn(move|| child_no(x+1)());
1274 thread::spawn(|| child_no(0)());
1278 fn test_simple_newsched_spawn() {
1279 thread::spawn(move || {});
1283 fn test_try_panic_message_static_str() {
1284 match thread::spawn(move|| {
1285 panic!("static string");
1288 type T = &'static str;
1289 assert!(e.is::<T>());
1290 assert_eq!(*e.downcast::<T>().unwrap(), "static string");
1297 fn test_try_panic_message_owned_str() {
1298 match thread::spawn(move|| {
1299 panic!("owned string".to_string());
1303 assert!(e.is::<T>());
1304 assert_eq!(*e.downcast::<T>().unwrap(), "owned string".to_string());
1311 fn test_try_panic_message_any() {
1312 match thread::spawn(move|| {
1313 panic!(box 413u16 as Box<Any + Send>);
1316 type T = Box<Any + Send>;
1317 assert!(e.is::<T>());
1318 let any = e.downcast::<T>().unwrap();
1319 assert!(any.is::<u16>());
1320 assert_eq!(*any.downcast::<u16>().unwrap(), 413);
1327 fn test_try_panic_message_unit_struct() {
1330 match thread::spawn(move|| {
1333 Err(ref e) if e.is::<Juju>() => {}
1334 Err(_) | Ok(()) => panic!()
1339 fn test_park_timeout_unpark_before() {
1341 thread::current().unpark();
1342 thread::park_timeout(Duration::from_millis(u32::MAX as u64));
1347 fn test_park_timeout_unpark_not_called() {
1349 thread::park_timeout(Duration::from_millis(10));
1354 fn test_park_timeout_unpark_called_other_thread() {
1356 let th = thread::current();
1358 let _guard = thread::spawn(move || {
1359 super::sleep(Duration::from_millis(50));
1363 thread::park_timeout(Duration::from_millis(u32::MAX as u64));
1368 fn sleep_ms_smoke() {
1369 thread::sleep(Duration::from_millis(2));
1373 fn test_thread_id_equal() {
1374 assert!(thread::current().id() == thread::current().id());
1378 fn test_thread_id_not_equal() {
1379 let spawned_id = thread::spawn(|| thread::current().id()).join().unwrap();
1380 assert!(thread::current().id() != spawned_id);
1383 // NOTE: the corresponding test for stderr is in run-pass/thread-stderr, due
1384 // to the test harness apparently interfering with stderr configuration.