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 //! ## Blocking support: park and unpark
101 //! Every thread is equipped with some basic low-level blocking support, via the
102 //! [`thread::park`][`park`] function and [`thread::Thread::unpark()`][`unpark`]
103 //! method. [`park`] blocks the current thread, which can then be resumed from
104 //! another thread by calling the [`unpark`] method on the blocked thread's handle.
106 //! Conceptually, each [`Thread`] handle has an associated token, which is
107 //! initially not present:
109 //! * The [`thread::park`][`park`] function blocks the current thread unless or until
110 //! the token is available for its thread handle, at which point it atomically
111 //! consumes the token. It may also return *spuriously*, without consuming the
112 //! token. [`thread::park_timeout`] does the same, but allows specifying a
113 //! maximum time to block the thread for.
115 //! * The [`unpark`] method on a [`Thread`] atomically makes the token available
116 //! if it wasn't already.
118 //! In other words, each [`Thread`] acts a bit like a semaphore with initial count
119 //! 0, except that the semaphore is *saturating* (the count cannot go above 1),
120 //! and can return spuriously.
122 //! The API is typically used by acquiring a handle to the current thread,
123 //! placing that handle in a shared data structure so that other threads can
124 //! find it, and then `park`ing. When some desired condition is met, another
125 //! thread calls [`unpark`] on the handle.
127 //! The motivation for this design is twofold:
129 //! * It avoids the need to allocate mutexes and condvars when building new
130 //! synchronization primitives; the threads already provide basic blocking/signaling.
132 //! * It can be implemented very efficiently on many platforms.
134 //! ## Thread-local storage
136 //! This module also provides an implementation of thread-local storage for Rust
137 //! programs. Thread-local storage is a method of storing data into a global
138 //! variable that each thread in the program will have its own copy of.
139 //! Threads do not share this data, so accesses do not need to be synchronized.
141 //! A thread-local key owns the value it contains and will destroy the value when the
142 //! thread exits. It is created with the [`thread_local!`] macro and can contain any
143 //! value that is `'static` (no borrowed pointers). It provides an accessor function,
144 //! [`with`], that yields a shared reference to the value to the specified
145 //! closure. Thread-local keys allow only shared access to values, as there would be no
146 //! way to guarantee uniqueness if mutable borrows were allowed. Most values
147 //! will want to make use of some form of **interior mutability** through the
148 //! [`Cell`] or [`RefCell`] types.
150 //! [channels]: ../../std/sync/mpsc/index.html
151 //! [`Arc`]: ../../std/sync/struct.Arc.html
152 //! [`spawn`]: ../../std/thread/fn.spawn.html
153 //! [`JoinHandle`]: ../../std/thread/struct.JoinHandle.html
154 //! [`JoinHandle::thread`]: ../../std/thread/struct.JoinHandle.html#method.thread
155 //! [`join`]: ../../std/thread/struct.JoinHandle.html#method.join
156 //! [`Result`]: ../../std/result/enum.Result.html
157 //! [`Ok`]: ../../std/result/enum.Result.html#variant.Ok
158 //! [`Err`]: ../../std/result/enum.Result.html#variant.Err
159 //! [`panic!`]: ../../std/macro.panic.html
160 //! [`Builder`]: ../../std/thread/struct.Builder.html
161 //! [`thread::current`]: ../../std/thread/fn.current.html
162 //! [`thread::Result`]: ../../std/thread/type.Result.html
163 //! [`Thread`]: ../../std/thread/struct.Thread.html
164 //! [`park`]: ../../std/thread/fn.park.html
165 //! [`unpark`]: ../../std/thread/struct.Thread.html#method.unpark
166 //! [`thread::park_timeout`]: ../../std/thread/fn.park_timeout.html
167 //! [`Cell`]: ../cell/struct.Cell.html
168 //! [`RefCell`]: ../cell/struct.RefCell.html
169 //! [`thread_local!`]: ../macro.thread_local.html
170 //! [`with`]: struct.LocalKey.html#method.with
172 #![stable(feature = "rust1", since = "1.0.0")]
175 use cell::UnsafeCell;
176 use ffi::{CStr, CString};
182 use sync::{Mutex, Condvar, Arc};
183 use sys::thread as imp;
184 use sys_common::mutex;
185 use sys_common::thread_info;
186 use sys_common::util;
187 use sys_common::{AsInner, IntoInner};
190 ////////////////////////////////////////////////////////////////////////////////
191 // Thread-local storage
192 ////////////////////////////////////////////////////////////////////////////////
194 #[macro_use] mod local;
196 #[stable(feature = "rust1", since = "1.0.0")]
197 pub use self::local::{LocalKey, LocalKeyState};
199 // The types used by the thread_local! macro to access TLS keys. Note that there
200 // are two types, the "OS" type and the "fast" type. The OS thread local key
201 // type is accessed via platform-specific API calls and is slow, while the fast
202 // key type is accessed via code generated via LLVM, where TLS keys are set up
203 // by the elf linker. Note that the OS TLS type is always available: on macOS
204 // the standard library is compiled with support for older platform versions
205 // where fast TLS was not available; end-user code is compiled with fast TLS
206 // where available, but both are needed.
208 #[unstable(feature = "libstd_thread_internals", issue = "0")]
209 #[cfg(target_thread_local)]
210 #[doc(hidden)] pub use sys::fast_thread_local::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 configuration. Provides detailed control over the properties
219 /// and behavior of new threads.
226 /// let builder = thread::Builder::new();
228 /// let handler = builder.spawn(|| {
232 /// handler.join().unwrap();
234 #[stable(feature = "rust1", since = "1.0.0")]
237 // A name for the thread-to-be, for identification in panic messages
238 name: Option<String>,
239 // The size of the stack for the spawned thread in bytes
240 stack_size: Option<usize>,
244 /// Generates the base configuration for spawning a thread, from which
245 /// configuration methods can be chained.
252 /// let builder = thread::Builder::new()
253 /// .name("foo".into())
256 /// let handler = builder.spawn(|| {
260 /// handler.join().unwrap();
262 #[stable(feature = "rust1", since = "1.0.0")]
263 pub fn new() -> Builder {
270 /// Names the thread-to-be. Currently the name is used for identification
271 /// only in panic messages.
278 /// let builder = thread::Builder::new()
279 /// .name("foo".into());
281 /// let handler = builder.spawn(|| {
282 /// assert_eq!(thread::current().name(), Some("foo"))
285 /// handler.join().unwrap();
287 #[stable(feature = "rust1", since = "1.0.0")]
288 pub fn name(mut self, name: String) -> Builder {
289 self.name = Some(name);
293 /// Sets the size of the stack (in bytes) for the new thread.
295 /// The actual stack size may be greater than this value if
296 /// the platform specifies minimal stack size.
303 /// let builder = thread::Builder::new().stack_size(32 * 1024);
305 #[stable(feature = "rust1", since = "1.0.0")]
306 pub fn stack_size(mut self, size: usize) -> Builder {
307 self.stack_size = Some(size);
311 /// Spawns a new thread, and returns a join handle for it.
313 /// The child thread may outlive the parent (unless the parent thread
314 /// is the main thread; the whole process is terminated when the main
315 /// thread finishes). The join handle can be used to block on
316 /// termination of the child thread, including recovering its panics.
320 /// Unlike the [`spawn`] free function, this method yields an
321 /// [`io::Result`] to capture any failure to create the thread at
324 /// [`spawn`]: ../../std/thread/fn.spawn.html
325 /// [`io::Result`]: ../../std/io/type.Result.html
332 /// let builder = thread::Builder::new();
334 /// let handler = builder.spawn(|| {
338 /// handler.join().unwrap();
340 #[stable(feature = "rust1", since = "1.0.0")]
341 pub fn spawn<F, T>(self, f: F) -> io::Result<JoinHandle<T>> where
342 F: FnOnce() -> T, F: Send + 'static, T: Send + 'static
344 let Builder { name, stack_size } = self;
346 let stack_size = stack_size.unwrap_or(util::min_stack());
348 let my_thread = Thread::new(name);
349 let their_thread = my_thread.clone();
351 let my_packet : Arc<UnsafeCell<Option<Result<T>>>>
352 = Arc::new(UnsafeCell::new(None));
353 let their_packet = my_packet.clone();
356 if let Some(name) = their_thread.cname() {
357 imp::Thread::set_name(name);
360 thread_info::set(imp::guard::current(), their_thread);
361 let try_result = panic::catch_unwind(panic::AssertUnwindSafe(f));
362 *their_packet.get() = Some(try_result);
366 Ok(JoinHandle(JoinInner {
368 Some(imp::Thread::new(stack_size, Box::new(main))?)
371 packet: Packet(my_packet),
376 ////////////////////////////////////////////////////////////////////////////////
378 ////////////////////////////////////////////////////////////////////////////////
380 /// Spawns a new thread, returning a [`JoinHandle`] for it.
382 /// The join handle will implicitly *detach* the child thread upon being
383 /// dropped. In this case, the child thread may outlive the parent (unless
384 /// the parent thread is the main thread; the whole process is terminated when
385 /// the main thread finishes). Additionally, the join handle provides a [`join`]
386 /// method that can be used to join the child thread. If the child thread
387 /// panics, [`join`] will return an [`Err`] containing the argument given to
392 /// Panics if the OS fails to create a thread; use [`Builder::spawn`]
393 /// to recover from such errors.
395 /// [`JoinHandle`]: ../../std/thread/struct.JoinHandle.html
396 /// [`join`]: ../../std/thread/struct.JoinHandle.html#method.join
397 /// [`Err`]: ../../std/result/enum.Result.html#variant.Err
398 /// [`panic`]: ../../std/macro.panic.html
399 /// [`Builder::spawn`]: ../../std/thread/struct.Builder.html#method.spawn
406 /// let handler = thread::spawn(|| {
410 /// handler.join().unwrap();
412 #[stable(feature = "rust1", since = "1.0.0")]
413 pub fn spawn<F, T>(f: F) -> JoinHandle<T> where
414 F: FnOnce() -> T, F: Send + 'static, T: Send + 'static
416 Builder::new().spawn(f).unwrap()
419 /// Gets a handle to the thread that invokes it.
423 /// Getting a handle to the current thread with `thread::current()`:
428 /// let handler = thread::Builder::new()
429 /// .name("named thread".into())
431 /// let handle = thread::current();
432 /// assert_eq!(handle.name(), Some("named thread"));
436 /// handler.join().unwrap();
438 #[stable(feature = "rust1", since = "1.0.0")]
439 pub fn current() -> Thread {
440 thread_info::current_thread().expect("use of std::thread::current() is not \
441 possible after the thread's local \
442 data has been destroyed")
445 /// Cooperatively gives up a timeslice to the OS scheduler.
452 /// thread::yield_now();
454 #[stable(feature = "rust1", since = "1.0.0")]
456 imp::Thread::yield_now()
459 /// Determines whether the current thread is unwinding because of panic.
466 /// struct SomeStruct;
468 /// impl Drop for SomeStruct {
469 /// fn drop(&mut self) {
470 /// if thread::panicking() {
471 /// println!("dropped while unwinding");
473 /// println!("dropped while not unwinding");
480 /// let a = SomeStruct;
485 /// let b = SomeStruct;
490 #[stable(feature = "rust1", since = "1.0.0")]
491 pub fn panicking() -> bool {
492 panicking::panicking()
495 /// Puts the current thread to sleep for the specified amount of time.
497 /// The thread may sleep longer than the duration specified due to scheduling
498 /// specifics or platform-dependent functionality.
500 /// # Platform behavior
502 /// On Unix platforms this function will not return early due to a
503 /// signal being received or a spurious wakeup.
510 /// // Let's sleep for 2 seconds:
511 /// thread::sleep_ms(2000);
513 #[stable(feature = "rust1", since = "1.0.0")]
514 #[rustc_deprecated(since = "1.6.0", reason = "replaced by `std::thread::sleep`")]
515 pub fn sleep_ms(ms: u32) {
516 sleep(Duration::from_millis(ms as u64))
519 /// Puts the current thread to sleep for the specified amount of time.
521 /// The thread may sleep longer than the duration specified due to scheduling
522 /// specifics or platform-dependent functionality.
524 /// # Platform behavior
526 /// On Unix platforms this function will not return early due to a
527 /// signal being received or a spurious wakeup. Platforms which do not support
528 /// nanosecond precision for sleeping will have `dur` rounded up to the nearest
529 /// granularity of time they can sleep for.
534 /// use std::{thread, time};
536 /// let ten_millis = time::Duration::from_millis(10);
537 /// let now = time::Instant::now();
539 /// thread::sleep(ten_millis);
541 /// assert!(now.elapsed() >= ten_millis);
543 #[stable(feature = "thread_sleep", since = "1.4.0")]
544 pub fn sleep(dur: Duration) {
545 imp::Thread::sleep(dur)
548 /// Blocks unless or until the current thread's token is made available.
550 /// Every thread is equipped with some basic low-level blocking support, via
551 /// the `park()` function and the [`unpark`][unpark] method. These can be
552 /// used as a more CPU-efficient implementation of a spinlock.
554 /// [unpark]: struct.Thread.html#method.unpark
556 /// The API is typically used by acquiring a handle to the current thread,
557 /// placing that handle in a shared data structure so that other threads can
558 /// find it, and then parking (in a loop with a check for the token actually
561 /// A call to `park` does not guarantee that the thread will remain parked
562 /// forever, and callers should be prepared for this possibility.
564 /// See the [module documentation][thread] for more detail.
566 /// [thread]: index.html
568 // The implementation currently uses the trivial strategy of a Mutex+Condvar
569 // with wakeup flag, which does not actually allow spurious wakeups. In the
570 // future, this will be implemented in a more efficient way, perhaps along the lines of
571 // http://cr.openjdk.java.net/~stefank/6989984.1/raw_files/new/src/os/linux/vm/os_linux.cpp
572 // or futuxes, and in either case may allow spurious wakeups.
573 #[stable(feature = "rust1", since = "1.0.0")]
575 let thread = current();
576 let mut guard = thread.inner.lock.lock().unwrap();
578 guard = thread.inner.cvar.wait(guard).unwrap();
583 /// Use [park_timeout].
585 /// Blocks unless or until the current thread's token is made available or
586 /// the specified duration has been reached (may wake spuriously).
588 /// The semantics of this function are equivalent to `park()` except that the
589 /// thread will be blocked for roughly no longer than `ms`. This method
590 /// should not be used for precise timing due to anomalies such as
591 /// preemption or platform differences that may not cause the maximum
592 /// amount of time waited to be precisely `ms` long.
594 /// See the [module documentation][thread] for more detail.
596 /// [thread]: index.html
597 /// [park_timeout]: fn.park_timeout.html
598 #[stable(feature = "rust1", since = "1.0.0")]
599 #[rustc_deprecated(since = "1.6.0", reason = "replaced by `std::thread::park_timeout`")]
600 pub fn park_timeout_ms(ms: u32) {
601 park_timeout(Duration::from_millis(ms as u64))
604 /// Blocks unless or until the current thread's token is made available or
605 /// the specified duration has been reached (may wake spuriously).
607 /// The semantics of this function are equivalent to `park()` except that the
608 /// thread will be blocked for roughly no longer than `dur`. This method
609 /// should not be used for precise timing due to anomalies such as
610 /// preemption or platform differences that may not cause the maximum
611 /// amount of time waited to be precisely `dur` long.
613 /// See the module doc for more detail.
615 /// # Platform behavior
617 /// Platforms which do not support nanosecond precision for sleeping will have
618 /// `dur` rounded up to the nearest granularity of time they can sleep for.
622 /// Waiting for the complete expiration of the timeout:
625 /// use std::thread::park_timeout;
626 /// use std::time::{Instant, Duration};
628 /// let timeout = Duration::from_secs(2);
629 /// let beginning_park = Instant::now();
630 /// park_timeout(timeout);
632 /// while beginning_park.elapsed() < timeout {
633 /// println!("restarting park_timeout after {:?}", beginning_park.elapsed());
634 /// let timeout = timeout - beginning_park.elapsed();
635 /// park_timeout(timeout);
638 #[stable(feature = "park_timeout", since = "1.4.0")]
639 pub fn park_timeout(dur: Duration) {
640 let thread = current();
641 let mut guard = thread.inner.lock.lock().unwrap();
643 let (g, _) = thread.inner.cvar.wait_timeout(guard, dur).unwrap();
649 ////////////////////////////////////////////////////////////////////////////////
651 ////////////////////////////////////////////////////////////////////////////////
653 /// A unique identifier for a running thread.
655 /// A `ThreadId` is an opaque object that has a unique value for each thread
656 /// that creates one. `ThreadId`s are not guaranteed to correspond to a thread's
657 /// system-designated identifier.
662 /// #![feature(thread_id)]
666 /// let other_thread = thread::spawn(|| {
667 /// thread::current().id()
670 /// let other_thread_id = other_thread.join().unwrap();
671 /// assert!(thread::current().id() != other_thread_id);
673 #[unstable(feature = "thread_id", issue = "21507")]
674 #[derive(Eq, PartialEq, Clone, Copy, Hash, Debug)]
675 pub struct ThreadId(u64);
678 // Generate a new unique thread ID.
679 fn new() -> ThreadId {
680 static GUARD: mutex::Mutex = mutex::Mutex::new();
681 static mut COUNTER: u64 = 0;
686 // If we somehow use up all our bits, panic so that we're not
687 // covering up subtle bugs of IDs being reused.
688 if COUNTER == ::u64::MAX {
690 panic!("failed to generate unique thread ID: bitspace exhausted");
703 ////////////////////////////////////////////////////////////////////////////////
705 ////////////////////////////////////////////////////////////////////////////////
707 /// The internal representation of a `Thread` handle
709 name: Option<CString>, // Guaranteed to be UTF-8
711 lock: Mutex<bool>, // true when there is a buffered unpark
716 #[stable(feature = "rust1", since = "1.0.0")]
717 /// A handle to a thread.
719 /// You can use it to identify a thread (by name, for example). Most of the
720 /// time, there is no need to directly create a `Thread` struct using the
721 /// constructor, instead you should use a function like `spawn` to create
722 /// new threads, see the docs of [`Builder`] and [`spawn`] for more.
727 /// use std::thread::Builder;
730 /// let thread_name = format!("thread_{}", i);
732 /// .name(thread_name) // Now you can identify which thread panicked
733 /// // thanks to the handle's name
736 /// panic!("I'm scared!!!");
742 /// [`Builder`]: ../../std/thread/struct.Builder.html
743 /// [`spawn`]: ../../std/thread/fn.spawn.html
750 // Used only internally to construct a thread object without spawning
751 pub(crate) fn new(name: Option<String>) -> Thread {
752 let cname = name.map(|n| {
753 CString::new(n).expect("thread name may not contain interior null bytes")
756 inner: Arc::new(Inner {
759 lock: Mutex::new(false),
760 cvar: Condvar::new(),
765 /// Atomically makes the handle's token available if it is not already.
767 /// See the module doc for more detail.
774 /// let handler = thread::Builder::new()
776 /// let thread = thread::current();
781 /// handler.join().unwrap();
783 #[stable(feature = "rust1", since = "1.0.0")]
784 pub fn unpark(&self) {
785 let mut guard = self.inner.lock.lock().unwrap();
788 self.inner.cvar.notify_one();
792 /// Gets the thread's unique identifier.
797 /// #![feature(thread_id)]
801 /// let other_thread = thread::spawn(|| {
802 /// thread::current().id()
805 /// let other_thread_id = other_thread.join().unwrap();
806 /// assert!(thread::current().id() != other_thread_id);
808 #[unstable(feature = "thread_id", issue = "21507")]
809 pub fn id(&self) -> ThreadId {
813 /// Gets the thread's name.
817 /// Threads by default have no name specified:
822 /// let builder = thread::Builder::new();
824 /// let handler = builder.spawn(|| {
825 /// assert!(thread::current().name().is_none());
828 /// handler.join().unwrap();
831 /// Thread with a specified name:
836 /// let builder = thread::Builder::new()
837 /// .name("foo".into());
839 /// let handler = builder.spawn(|| {
840 /// assert_eq!(thread::current().name(), Some("foo"))
843 /// handler.join().unwrap();
845 #[stable(feature = "rust1", since = "1.0.0")]
846 pub fn name(&self) -> Option<&str> {
847 self.cname().map(|s| unsafe { str::from_utf8_unchecked(s.to_bytes()) } )
850 fn cname(&self) -> Option<&CStr> {
851 self.inner.name.as_ref().map(|s| &**s)
855 #[stable(feature = "rust1", since = "1.0.0")]
856 impl fmt::Debug for Thread {
857 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
858 fmt::Debug::fmt(&self.name(), f)
862 ////////////////////////////////////////////////////////////////////////////////
864 ////////////////////////////////////////////////////////////////////////////////
866 /// Indicates the manner in which a thread exited.
868 /// A thread that completes without panicking is considered to exit successfully.
869 #[stable(feature = "rust1", since = "1.0.0")]
870 pub type Result<T> = ::result::Result<T, Box<Any + Send + 'static>>;
872 // This packet is used to communicate the return value between the child thread
873 // and the parent thread. Memory is shared through the `Arc` within and there's
874 // no need for a mutex here because synchronization happens with `join()` (the
875 // parent thread never reads this packet until the child has exited).
877 // This packet itself is then stored into a `JoinInner` which in turns is placed
878 // in `JoinHandle` and `JoinGuard`. Due to the usage of `UnsafeCell` we need to
879 // manually worry about impls like Send and Sync. The type `T` should
880 // already always be Send (otherwise the thread could not have been created) and
881 // this type is inherently Sync because no methods take &self. Regardless,
882 // however, we add inheriting impls for Send/Sync to this type to ensure it's
883 // Send/Sync and that future modifications will still appropriately classify it.
884 struct Packet<T>(Arc<UnsafeCell<Option<Result<T>>>>);
886 unsafe impl<T: Send> Send for Packet<T> {}
887 unsafe impl<T: Sync> Sync for Packet<T> {}
889 /// Inner representation for JoinHandle
890 struct JoinInner<T> {
891 native: Option<imp::Thread>,
896 impl<T> JoinInner<T> {
897 fn join(&mut self) -> Result<T> {
898 self.native.take().unwrap().join();
900 (*self.packet.0.get()).take().unwrap()
905 /// An owned permission to join on a thread (block on its termination).
907 /// A `JoinHandle` *detaches* the child thread when it is dropped.
909 /// Due to platform restrictions, it is not possible to [`Clone`] this
910 /// handle: the ability to join a child thread is a uniquely-owned
913 /// This `struct` is created by the [`thread::spawn`] function and the
914 /// [`thread::Builder::spawn`] method.
918 /// Creation from [`thread::spawn`]:
923 /// let join_handle: thread::JoinHandle<_> = thread::spawn(|| {
924 /// // some work here
928 /// Creation from [`thread::Builder::spawn`]:
933 /// let builder = thread::Builder::new();
935 /// let join_handle: thread::JoinHandle<_> = builder.spawn(|| {
936 /// // some work here
940 /// [`Clone`]: ../../std/clone/trait.Clone.html
941 /// [`thread::spawn`]: fn.spawn.html
942 /// [`thread::Builder::spawn`]: struct.Builder.html#method.spawn
943 #[stable(feature = "rust1", since = "1.0.0")]
944 pub struct JoinHandle<T>(JoinInner<T>);
946 impl<T> JoinHandle<T> {
947 /// Extracts a handle to the underlying thread.
952 /// #![feature(thread_id)]
956 /// let builder = thread::Builder::new();
958 /// let join_handle: thread::JoinHandle<_> = builder.spawn(|| {
959 /// // some work here
962 /// let thread = join_handle.thread();
963 /// println!("thread id: {:?}", thread.id());
965 #[stable(feature = "rust1", since = "1.0.0")]
966 pub fn thread(&self) -> &Thread {
970 /// Waits for the associated thread to finish.
972 /// If the child thread panics, [`Err`] is returned with the parameter given
975 /// [`Err`]: ../../std/result/enum.Result.html#variant.Err
976 /// [`panic`]: ../../std/macro.panic.html
983 /// let builder = thread::Builder::new();
985 /// let join_handle: thread::JoinHandle<_> = builder.spawn(|| {
986 /// // some work here
988 /// join_handle.join().expect("Couldn't join on the associated thread");
990 #[stable(feature = "rust1", since = "1.0.0")]
991 pub fn join(mut self) -> Result<T> {
996 impl<T> AsInner<imp::Thread> for JoinHandle<T> {
997 fn as_inner(&self) -> &imp::Thread { self.0.native.as_ref().unwrap() }
1000 impl<T> IntoInner<imp::Thread> for JoinHandle<T> {
1001 fn into_inner(self) -> imp::Thread { self.0.native.unwrap() }
1004 #[stable(feature = "std_debug", since = "1.16.0")]
1005 impl<T> fmt::Debug for JoinHandle<T> {
1006 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1007 f.pad("JoinHandle { .. }")
1011 fn _assert_sync_and_send() {
1012 fn _assert_both<T: Send + Sync>() {}
1013 _assert_both::<JoinHandle<()>>();
1014 _assert_both::<Thread>();
1017 ////////////////////////////////////////////////////////////////////////////////
1019 ////////////////////////////////////////////////////////////////////////////////
1021 #[cfg(all(test, not(target_os = "emscripten")))]
1024 use sync::mpsc::{channel, Sender};
1026 use super::{Builder};
1031 // !!! These tests are dangerous. If something is buggy, they will hang, !!!
1032 // !!! instead of exiting cleanly. This might wedge the buildbots. !!!
1035 fn test_unnamed_thread() {
1036 thread::spawn(move|| {
1037 assert!(thread::current().name().is_none());
1038 }).join().ok().unwrap();
1042 fn test_named_thread() {
1043 Builder::new().name("ada lovelace".to_string()).spawn(move|| {
1044 assert!(thread::current().name().unwrap() == "ada lovelace".to_string());
1045 }).unwrap().join().unwrap();
1050 fn test_invalid_named_thread() {
1051 let _ = Builder::new().name("ada l\0velace".to_string()).spawn(|| {});
1055 fn test_run_basic() {
1056 let (tx, rx) = channel();
1057 thread::spawn(move|| {
1058 tx.send(()).unwrap();
1064 fn test_join_panic() {
1065 match thread::spawn(move|| {
1068 result::Result::Err(_) => (),
1069 result::Result::Ok(()) => panic!()
1074 fn test_spawn_sched() {
1075 let (tx, rx) = channel();
1077 fn f(i: i32, tx: Sender<()>) {
1078 let tx = tx.clone();
1079 thread::spawn(move|| {
1081 tx.send(()).unwrap();
1093 fn test_spawn_sched_childs_on_default_sched() {
1094 let (tx, rx) = channel();
1096 thread::spawn(move|| {
1097 thread::spawn(move|| {
1098 tx.send(()).unwrap();
1105 fn avoid_copying_the_body<F>(spawnfn: F) where F: FnOnce(Box<Fn() + Send>) {
1106 let (tx, rx) = channel();
1108 let x: Box<_> = box 1;
1109 let x_in_parent = (&*x) as *const i32 as usize;
1111 spawnfn(Box::new(move|| {
1112 let x_in_child = (&*x) as *const i32 as usize;
1113 tx.send(x_in_child).unwrap();
1116 let x_in_child = rx.recv().unwrap();
1117 assert_eq!(x_in_parent, x_in_child);
1121 fn test_avoid_copying_the_body_spawn() {
1122 avoid_copying_the_body(|v| {
1123 thread::spawn(move || v());
1128 fn test_avoid_copying_the_body_thread_spawn() {
1129 avoid_copying_the_body(|f| {
1130 thread::spawn(move|| {
1137 fn test_avoid_copying_the_body_join() {
1138 avoid_copying_the_body(|f| {
1139 let _ = thread::spawn(move|| {
1146 fn test_child_doesnt_ref_parent() {
1147 // If the child refcounts the parent thread, this will stack overflow when
1148 // climbing the thread tree to dereference each ancestor. (See #1789)
1149 // (well, it would if the constant were 8000+ - I lowered it to be more
1150 // valgrind-friendly. try this at home, instead..!)
1151 const GENERATIONS: u32 = 16;
1152 fn child_no(x: u32) -> Box<Fn() + Send> {
1153 return Box::new(move|| {
1154 if x < GENERATIONS {
1155 thread::spawn(move|| child_no(x+1)());
1159 thread::spawn(|| child_no(0)());
1163 fn test_simple_newsched_spawn() {
1164 thread::spawn(move || {});
1168 fn test_try_panic_message_static_str() {
1169 match thread::spawn(move|| {
1170 panic!("static string");
1173 type T = &'static str;
1174 assert!(e.is::<T>());
1175 assert_eq!(*e.downcast::<T>().unwrap(), "static string");
1182 fn test_try_panic_message_owned_str() {
1183 match thread::spawn(move|| {
1184 panic!("owned string".to_string());
1188 assert!(e.is::<T>());
1189 assert_eq!(*e.downcast::<T>().unwrap(), "owned string".to_string());
1196 fn test_try_panic_message_any() {
1197 match thread::spawn(move|| {
1198 panic!(box 413u16 as Box<Any + Send>);
1201 type T = Box<Any + Send>;
1202 assert!(e.is::<T>());
1203 let any = e.downcast::<T>().unwrap();
1204 assert!(any.is::<u16>());
1205 assert_eq!(*any.downcast::<u16>().unwrap(), 413);
1212 fn test_try_panic_message_unit_struct() {
1215 match thread::spawn(move|| {
1218 Err(ref e) if e.is::<Juju>() => {}
1219 Err(_) | Ok(()) => panic!()
1224 fn test_park_timeout_unpark_before() {
1226 thread::current().unpark();
1227 thread::park_timeout(Duration::from_millis(u32::MAX as u64));
1232 fn test_park_timeout_unpark_not_called() {
1234 thread::park_timeout(Duration::from_millis(10));
1239 fn test_park_timeout_unpark_called_other_thread() {
1241 let th = thread::current();
1243 let _guard = thread::spawn(move || {
1244 super::sleep(Duration::from_millis(50));
1248 thread::park_timeout(Duration::from_millis(u32::MAX as u64));
1253 fn sleep_ms_smoke() {
1254 thread::sleep(Duration::from_millis(2));
1258 fn test_thread_id_equal() {
1259 assert!(thread::current().id() == thread::current().id());
1263 fn test_thread_id_not_equal() {
1264 let spawned_id = thread::spawn(|| thread::current().id()).join().unwrap();
1265 assert!(thread::current().id() != spawned_id);
1268 // NOTE: the corresponding test for stderr is in run-pass/thread-stderr, due
1269 // to the test harness apparently interfering with stderr configuration.