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 [`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()`] 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 //! [`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.spawn.html
162 //! [`Thread`]: ../../std/thread/struct.Thread.html
163 //! [`park()`]: ../../std/thread/fn.park.html
164 //! [`unpark()`]: ../../std/thread/struct.Thread.html#method.unpark
165 //! [`thread::park_timeout()`]: ../../std/thread/fn.park_timeout.html
166 //! [`Cell`]: ../cell/struct.Cell.html
167 //! [`RefCell`]: ../cell/struct.RefCell.html
168 //! [`thread_local!`]: ../macro.thread_local.html
169 //! [`with`]: struct.LocalKey.html#method.with
171 #![stable(feature = "rust1", since = "1.0.0")]
174 use cell::UnsafeCell;
175 use ffi::{CStr, CString};
181 use sync::{Mutex, Condvar, Arc};
182 use sys::thread as imp;
183 use sys_common::mutex;
184 use sys_common::thread_info;
185 use sys_common::util;
186 use sys_common::{AsInner, IntoInner};
189 ////////////////////////////////////////////////////////////////////////////////
190 // Thread-local storage
191 ////////////////////////////////////////////////////////////////////////////////
193 #[macro_use] mod local;
195 #[stable(feature = "rust1", since = "1.0.0")]
196 pub use self::local::{LocalKey, LocalKeyState};
198 // The types used by the thread_local! macro to access TLS keys. Note that there
199 // are two types, the "OS" type and the "fast" type. The OS thread local key
200 // type is accessed via platform-specific API calls and is slow, while the fast
201 // key type is accessed via code generated via LLVM, where TLS keys are set up
202 // by the elf linker. Note that the OS TLS type is always available: on macOS
203 // the standard library is compiled with support for older platform versions
204 // where fast TLS was not available; end-user code is compiled with fast TLS
205 // where available, but both are needed.
207 #[unstable(feature = "libstd_thread_internals", issue = "0")]
208 #[cfg(target_thread_local)]
209 #[doc(hidden)] pub use sys::fast_thread_local::Key as __FastLocalKeyInner;
210 #[unstable(feature = "libstd_thread_internals", issue = "0")]
211 #[doc(hidden)] pub use self::local::os::Key as __OsLocalKeyInner;
213 ////////////////////////////////////////////////////////////////////////////////
215 ////////////////////////////////////////////////////////////////////////////////
217 /// Thread configuration. Provides detailed control over the properties
218 /// and behavior of new threads.
225 /// let builder = thread::Builder::new();
227 /// let handler = builder.spawn(|| {
231 /// handler.join().unwrap();
233 #[stable(feature = "rust1", since = "1.0.0")]
236 // A name for the thread-to-be, for identification in panic messages
237 name: Option<String>,
238 // The size of the stack for the spawned thread
239 stack_size: Option<usize>,
243 /// Generates the base configuration for spawning a thread, from which
244 /// configuration methods can be chained.
251 /// let builder = thread::Builder::new()
252 /// .name("foo".into())
255 /// let handler = builder.spawn(|| {
259 /// handler.join().unwrap();
261 #[stable(feature = "rust1", since = "1.0.0")]
262 pub fn new() -> Builder {
269 /// Names the thread-to-be. Currently the name is used for identification
270 /// only in panic messages.
277 /// let builder = thread::Builder::new()
278 /// .name("foo".into());
280 /// let handler = builder.spawn(|| {
281 /// assert_eq!(thread::current().name(), Some("foo"))
284 /// handler.join().unwrap();
286 #[stable(feature = "rust1", since = "1.0.0")]
287 pub fn name(mut self, name: String) -> Builder {
288 self.name = Some(name);
292 /// Sets the size of the stack for the new thread.
299 /// let builder = thread::Builder::new().stack_size(10);
301 #[stable(feature = "rust1", since = "1.0.0")]
302 pub fn stack_size(mut self, size: usize) -> Builder {
303 self.stack_size = Some(size);
307 /// Spawns a new thread, and returns a join handle for it.
309 /// The child thread may outlive the parent (unless the parent thread
310 /// is the main thread; the whole process is terminated when the main
311 /// thread finishes). The join handle can be used to block on
312 /// termination of the child thread, including recovering its panics.
316 /// Unlike the [`spawn`] free function, this method yields an
317 /// [`io::Result`] to capture any failure to create the thread at
320 /// [`spawn`]: ../../std/thread/fn.spawn.html
321 /// [`io::Result`]: ../../std/io/type.Result.html
328 /// let builder = thread::Builder::new();
330 /// let handler = builder.spawn(|| {
334 /// handler.join().unwrap();
336 #[stable(feature = "rust1", since = "1.0.0")]
337 pub fn spawn<F, T>(self, f: F) -> io::Result<JoinHandle<T>> where
338 F: FnOnce() -> T, F: Send + 'static, T: Send + 'static
340 let Builder { name, stack_size } = self;
342 let stack_size = stack_size.unwrap_or(util::min_stack());
344 let my_thread = Thread::new(name);
345 let their_thread = my_thread.clone();
347 let my_packet : Arc<UnsafeCell<Option<Result<T>>>>
348 = Arc::new(UnsafeCell::new(None));
349 let their_packet = my_packet.clone();
352 if let Some(name) = their_thread.cname() {
353 imp::Thread::set_name(name);
356 thread_info::set(imp::guard::current(), their_thread);
357 let try_result = panic::catch_unwind(panic::AssertUnwindSafe(f));
358 *their_packet.get() = Some(try_result);
362 Ok(JoinHandle(JoinInner {
364 Some(imp::Thread::new(stack_size, Box::new(main))?)
367 packet: Packet(my_packet),
372 ////////////////////////////////////////////////////////////////////////////////
374 ////////////////////////////////////////////////////////////////////////////////
376 /// Spawns a new thread, returning a [`JoinHandle`] for it.
378 /// The join handle will implicitly *detach* the child thread upon being
379 /// dropped. In this case, the child thread may outlive the parent (unless
380 /// the parent thread is the main thread; the whole process is terminated when
381 /// the main thread finishes). Additionally, the join handle provides a [`join`]
382 /// method that can be used to join the child thread. If the child thread
383 /// panics, [`join`] will return an [`Err`] containing the argument given to
388 /// Panics if the OS fails to create a thread; use [`Builder::spawn`]
389 /// to recover from such errors.
391 /// [`JoinHandle`]: ../../std/thread/struct.JoinHandle.html
392 /// [`join`]: ../../std/thread/struct.JoinHandle.html#method.join
393 /// [`Err`]: ../../std/result/enum.Result.html#variant.Err
394 /// [`panic`]: ../../std/macro.panic.html
395 /// [`Builder::spawn`]: ../../std/thread/struct.Builder.html#method.spawn
402 /// let handler = thread::spawn(|| {
406 /// handler.join().unwrap();
408 #[stable(feature = "rust1", since = "1.0.0")]
409 pub fn spawn<F, T>(f: F) -> JoinHandle<T> where
410 F: FnOnce() -> T, F: Send + 'static, T: Send + 'static
412 Builder::new().spawn(f).unwrap()
415 /// Gets a handle to the thread that invokes it.
419 /// Getting a handle to the current thread with `thread::current()`:
424 /// let handler = thread::Builder::new()
425 /// .name("named thread".into())
427 /// let handle = thread::current();
428 /// assert_eq!(handle.name(), Some("named thread"));
432 /// handler.join().unwrap();
434 #[stable(feature = "rust1", since = "1.0.0")]
435 pub fn current() -> Thread {
436 thread_info::current_thread().expect("use of std::thread::current() is not \
437 possible after the thread's local \
438 data has been destroyed")
441 /// Cooperatively gives up a timeslice to the OS scheduler.
448 /// thread::yield_now();
450 #[stable(feature = "rust1", since = "1.0.0")]
452 imp::Thread::yield_now()
455 /// Determines whether the current thread is unwinding because of panic.
462 /// struct SomeStruct;
464 /// impl Drop for SomeStruct {
465 /// fn drop(&mut self) {
466 /// if thread::panicking() {
467 /// println!("dropped while unwinding");
469 /// println!("dropped while not unwinding");
476 /// let a = SomeStruct;
481 /// let b = SomeStruct;
486 #[stable(feature = "rust1", since = "1.0.0")]
487 pub fn panicking() -> bool {
488 panicking::panicking()
491 /// Puts the current thread to sleep for the specified amount of time.
493 /// The thread may sleep longer than the duration specified due to scheduling
494 /// specifics or platform-dependent functionality.
496 /// # Platform behavior
498 /// On Unix platforms this function will not return early due to a
499 /// signal being received or a spurious wakeup.
506 /// // Let's sleep for 2 seconds:
507 /// thread::sleep_ms(2000);
509 #[stable(feature = "rust1", since = "1.0.0")]
510 #[rustc_deprecated(since = "1.6.0", reason = "replaced by `std::thread::sleep`")]
511 pub fn sleep_ms(ms: u32) {
512 sleep(Duration::from_millis(ms as u64))
515 /// Puts the current thread to sleep for the specified amount of time.
517 /// The thread may sleep longer than the duration specified due to scheduling
518 /// specifics or platform-dependent functionality.
520 /// # Platform behavior
522 /// On Unix platforms this function will not return early due to a
523 /// signal being received or a spurious wakeup. Platforms which do not support
524 /// nanosecond precision for sleeping will have `dur` rounded up to the nearest
525 /// granularity of time they can sleep for.
530 /// use std::{thread, time};
532 /// let ten_millis = time::Duration::from_millis(10);
533 /// let now = time::Instant::now();
535 /// thread::sleep(ten_millis);
537 /// assert!(now.elapsed() >= ten_millis);
539 #[stable(feature = "thread_sleep", since = "1.4.0")]
540 pub fn sleep(dur: Duration) {
541 imp::Thread::sleep(dur)
544 /// Blocks unless or until the current thread's token is made available.
546 /// Every thread is equipped with some basic low-level blocking support, via
547 /// the `park()` function and the [`unpark()`][unpark] method. These can be
548 /// used as a more CPU-efficient implementation of a spinlock.
550 /// [unpark]: struct.Thread.html#method.unpark
552 /// The API is typically used by acquiring a handle to the current thread,
553 /// placing that handle in a shared data structure so that other threads can
554 /// find it, and then parking (in a loop with a check for the token actually
557 /// A call to `park` does not guarantee that the thread will remain parked
558 /// forever, and callers should be prepared for this possibility.
560 /// See the [module documentation][thread] for more detail.
562 /// [thread]: index.html
564 // The implementation currently uses the trivial strategy of a Mutex+Condvar
565 // with wakeup flag, which does not actually allow spurious wakeups. In the
566 // future, this will be implemented in a more efficient way, perhaps along the lines of
567 // http://cr.openjdk.java.net/~stefank/6989984.1/raw_files/new/src/os/linux/vm/os_linux.cpp
568 // or futuxes, and in either case may allow spurious wakeups.
569 #[stable(feature = "rust1", since = "1.0.0")]
571 let thread = current();
572 let mut guard = thread.inner.lock.lock().unwrap();
574 guard = thread.inner.cvar.wait(guard).unwrap();
579 /// Use [park_timeout].
581 /// Blocks unless or until the current thread's token is made available or
582 /// the specified duration has been reached (may wake spuriously).
584 /// The semantics of this function are equivalent to `park()` except that the
585 /// thread will be blocked for roughly no longer than `ms`. This method
586 /// should not be used for precise timing due to anomalies such as
587 /// preemption or platform differences that may not cause the maximum
588 /// amount of time waited to be precisely `ms` long.
590 /// See the [module documentation][thread] for more detail.
592 /// [thread]: index.html
593 /// [park_timeout]: fn.park_timeout.html
594 #[stable(feature = "rust1", since = "1.0.0")]
595 #[rustc_deprecated(since = "1.6.0", reason = "replaced by `std::thread::park_timeout`")]
596 pub fn park_timeout_ms(ms: u32) {
597 park_timeout(Duration::from_millis(ms as u64))
600 /// Blocks unless or until the current thread's token is made available or
601 /// the specified duration has been reached (may wake spuriously).
603 /// The semantics of this function are equivalent to `park()` except that the
604 /// thread will be blocked for roughly no longer than `dur`. This method
605 /// should not be used for precise timing due to anomalies such as
606 /// preemption or platform differences that may not cause the maximum
607 /// amount of time waited to be precisely `dur` long.
609 /// See the module doc for more detail.
611 /// # Platform behavior
613 /// Platforms which do not support nanosecond precision for sleeping will have
614 /// `dur` rounded up to the nearest granularity of time they can sleep for.
618 /// Waiting for the complete expiration of the timeout:
621 /// use std::thread::park_timeout;
622 /// use std::time::{Instant, Duration};
624 /// let timeout = Duration::from_secs(2);
625 /// let beginning_park = Instant::now();
626 /// park_timeout(timeout);
628 /// while beginning_park.elapsed() < timeout {
629 /// println!("restarting park_timeout after {:?}", beginning_park.elapsed());
630 /// let timeout = timeout - beginning_park.elapsed();
631 /// park_timeout(timeout);
634 #[stable(feature = "park_timeout", since = "1.4.0")]
635 pub fn park_timeout(dur: Duration) {
636 let thread = current();
637 let mut guard = thread.inner.lock.lock().unwrap();
639 let (g, _) = thread.inner.cvar.wait_timeout(guard, dur).unwrap();
645 ////////////////////////////////////////////////////////////////////////////////
647 ////////////////////////////////////////////////////////////////////////////////
649 /// A unique identifier for a running thread.
651 /// A `ThreadId` is an opaque object that has a unique value for each thread
652 /// that creates one. `ThreadId`s do not correspond to a thread's system-
653 /// designated identifier.
658 /// #![feature(thread_id)]
662 /// let handler = thread::Builder::new()
664 /// let thread = thread::current();
665 /// let thread_id = thread.id();
669 /// handler.join().unwrap();
671 #[unstable(feature = "thread_id", issue = "21507")]
672 #[derive(Eq, PartialEq, Copy, Clone)]
673 pub struct ThreadId(u64);
676 // Generate a new unique thread ID.
677 fn new() -> ThreadId {
678 static GUARD: mutex::Mutex = mutex::Mutex::new();
679 static mut COUNTER: u64 = 0;
684 // If we somehow use up all our bits, panic so that we're not
685 // covering up subtle bugs of IDs being reused.
686 if COUNTER == ::u64::MAX {
688 panic!("failed to generate unique thread ID: bitspace exhausted");
701 #[unstable(feature = "thread_id", issue = "21507")]
702 impl fmt::Debug for ThreadId {
703 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
704 f.pad("ThreadId { .. }")
708 ////////////////////////////////////////////////////////////////////////////////
710 ////////////////////////////////////////////////////////////////////////////////
712 /// The internal representation of a `Thread` handle
714 name: Option<CString>, // Guaranteed to be UTF-8
716 lock: Mutex<bool>, // true when there is a buffered unpark
721 #[stable(feature = "rust1", since = "1.0.0")]
722 /// A handle to a thread.
729 /// let handler = thread::Builder::new()
730 /// .name("foo".into())
732 /// let thread = thread::current();
733 /// println!("thread name: {}", thread.name().unwrap());
737 /// handler.join().unwrap();
744 // Used only internally to construct a thread object without spawning
745 fn new(name: Option<String>) -> Thread {
746 let cname = name.map(|n| {
747 CString::new(n).expect("thread name may not contain interior null bytes")
750 inner: Arc::new(Inner {
753 lock: Mutex::new(false),
754 cvar: Condvar::new(),
759 /// Atomically makes the handle's token available if it is not already.
761 /// See the module doc for more detail.
768 /// let handler = thread::Builder::new()
770 /// let thread = thread::current();
775 /// handler.join().unwrap();
777 #[stable(feature = "rust1", since = "1.0.0")]
778 pub fn unpark(&self) {
779 let mut guard = self.inner.lock.lock().unwrap();
782 self.inner.cvar.notify_one();
786 /// Gets the thread's unique identifier.
791 /// #![feature(thread_id)]
795 /// let handler = thread::Builder::new()
797 /// let thread = thread::current();
798 /// println!("thread id: {:?}", thread.id());
802 /// handler.join().unwrap();
804 #[unstable(feature = "thread_id", issue = "21507")]
805 pub fn id(&self) -> ThreadId {
809 /// Gets the thread's name.
813 /// Threads by default have no name specified:
818 /// let builder = thread::Builder::new();
820 /// let handler = builder.spawn(|| {
821 /// assert!(thread::current().name().is_none());
824 /// handler.join().unwrap();
827 /// Thread with a specified name:
832 /// let builder = thread::Builder::new()
833 /// .name("foo".into());
835 /// let handler = builder.spawn(|| {
836 /// assert_eq!(thread::current().name(), Some("foo"))
839 /// handler.join().unwrap();
841 #[stable(feature = "rust1", since = "1.0.0")]
842 pub fn name(&self) -> Option<&str> {
843 self.cname().map(|s| unsafe { str::from_utf8_unchecked(s.to_bytes()) } )
846 fn cname(&self) -> Option<&CStr> {
847 self.inner.name.as_ref().map(|s| &**s)
851 #[stable(feature = "rust1", since = "1.0.0")]
852 impl fmt::Debug for Thread {
853 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
854 fmt::Debug::fmt(&self.name(), f)
858 // a hack to get around privacy restrictions
859 impl thread_info::NewThread for Thread {
860 fn new(name: Option<String>) -> Thread { Thread::new(name) }
863 ////////////////////////////////////////////////////////////////////////////////
865 ////////////////////////////////////////////////////////////////////////////////
867 /// Indicates the manner in which a thread exited.
869 /// A thread that completes without panicking is considered to exit successfully.
870 #[stable(feature = "rust1", since = "1.0.0")]
871 pub type Result<T> = ::result::Result<T, Box<Any + Send + 'static>>;
873 // This packet is used to communicate the return value between the child thread
874 // and the parent thread. Memory is shared through the `Arc` within and there's
875 // no need for a mutex here because synchronization happens with `join()` (the
876 // parent thread never reads this packet until the child has exited).
878 // This packet itself is then stored into a `JoinInner` which in turns is placed
879 // in `JoinHandle` and `JoinGuard`. Due to the usage of `UnsafeCell` we need to
880 // manually worry about impls like Send and Sync. The type `T` should
881 // already always be Send (otherwise the thread could not have been created) and
882 // this type is inherently Sync because no methods take &self. Regardless,
883 // however, we add inheriting impls for Send/Sync to this type to ensure it's
884 // Send/Sync and that future modifications will still appropriately classify it.
885 struct Packet<T>(Arc<UnsafeCell<Option<Result<T>>>>);
887 unsafe impl<T: Send> Send for Packet<T> {}
888 unsafe impl<T: Sync> Sync for Packet<T> {}
890 /// Inner representation for JoinHandle
891 struct JoinInner<T> {
892 native: Option<imp::Thread>,
897 impl<T> JoinInner<T> {
898 fn join(&mut self) -> Result<T> {
899 self.native.take().unwrap().join();
901 (*self.packet.0.get()).take().unwrap()
906 /// An owned permission to join on a thread (block on its termination).
908 /// A `JoinHandle` *detaches* the child thread when it is dropped.
910 /// Due to platform restrictions, it is not possible to [`Clone`] this
911 /// handle: the ability to join a child thread is a uniquely-owned
914 /// This `struct` is created by the [`thread::spawn`] function and the
915 /// [`thread::Builder::spawn`] method.
919 /// Creation from [`thread::spawn`]:
924 /// let join_handle: thread::JoinHandle<_> = thread::spawn(|| {
925 /// // some work here
929 /// Creation from [`thread::Builder::spawn`]:
934 /// let builder = thread::Builder::new();
936 /// let join_handle: thread::JoinHandle<_> = builder.spawn(|| {
937 /// // some work here
941 /// [`Clone`]: ../../std/clone/trait.Clone.html
942 /// [`thread::spawn`]: fn.spawn.html
943 /// [`thread::Builder::spawn`]: struct.Builder.html#method.spawn
944 #[stable(feature = "rust1", since = "1.0.0")]
945 pub struct JoinHandle<T>(JoinInner<T>);
947 impl<T> JoinHandle<T> {
948 /// Extracts a handle to the underlying thread.
953 /// #![feature(thread_id)]
957 /// let builder = thread::Builder::new();
959 /// let join_handle: thread::JoinHandle<_> = builder.spawn(|| {
960 /// // some work here
963 /// let thread = join_handle.thread();
964 /// println!("thread id: {:?}", thread.id());
966 #[stable(feature = "rust1", since = "1.0.0")]
967 pub fn thread(&self) -> &Thread {
971 /// Waits for the associated thread to finish.
973 /// If the child thread panics, [`Err`] is returned with the parameter given
976 /// [`Err`]: ../../std/result/enum.Result.html#variant.Err
977 /// [`panic`]: ../../std/macro.panic.html
984 /// let builder = thread::Builder::new();
986 /// let join_handle: thread::JoinHandle<_> = builder.spawn(|| {
987 /// // some work here
989 /// join_handle.join().expect("Couldn't join on the associated thread");
991 #[stable(feature = "rust1", since = "1.0.0")]
992 pub fn join(mut self) -> Result<T> {
997 impl<T> AsInner<imp::Thread> for JoinHandle<T> {
998 fn as_inner(&self) -> &imp::Thread { self.0.native.as_ref().unwrap() }
1001 impl<T> IntoInner<imp::Thread> for JoinHandle<T> {
1002 fn into_inner(self) -> imp::Thread { self.0.native.unwrap() }
1005 #[stable(feature = "std_debug", since = "1.16.0")]
1006 impl<T> fmt::Debug for JoinHandle<T> {
1007 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1008 f.pad("JoinHandle { .. }")
1012 fn _assert_sync_and_send() {
1013 fn _assert_both<T: Send + Sync>() {}
1014 _assert_both::<JoinHandle<()>>();
1015 _assert_both::<Thread>();
1018 ////////////////////////////////////////////////////////////////////////////////
1020 ////////////////////////////////////////////////////////////////////////////////
1022 #[cfg(all(test, not(target_os = "emscripten")))]
1025 use sync::mpsc::{channel, Sender};
1027 use super::{Builder};
1032 // !!! These tests are dangerous. If something is buggy, they will hang, !!!
1033 // !!! instead of exiting cleanly. This might wedge the buildbots. !!!
1036 fn test_unnamed_thread() {
1037 thread::spawn(move|| {
1038 assert!(thread::current().name().is_none());
1039 }).join().ok().unwrap();
1043 fn test_named_thread() {
1044 Builder::new().name("ada lovelace".to_string()).spawn(move|| {
1045 assert!(thread::current().name().unwrap() == "ada lovelace".to_string());
1046 }).unwrap().join().unwrap();
1051 fn test_invalid_named_thread() {
1052 let _ = Builder::new().name("ada l\0velace".to_string()).spawn(|| {});
1056 fn test_run_basic() {
1057 let (tx, rx) = channel();
1058 thread::spawn(move|| {
1059 tx.send(()).unwrap();
1065 fn test_join_panic() {
1066 match thread::spawn(move|| {
1069 result::Result::Err(_) => (),
1070 result::Result::Ok(()) => panic!()
1075 fn test_spawn_sched() {
1076 let (tx, rx) = channel();
1078 fn f(i: i32, tx: Sender<()>) {
1079 let tx = tx.clone();
1080 thread::spawn(move|| {
1082 tx.send(()).unwrap();
1094 fn test_spawn_sched_childs_on_default_sched() {
1095 let (tx, rx) = channel();
1097 thread::spawn(move|| {
1098 thread::spawn(move|| {
1099 tx.send(()).unwrap();
1106 fn avoid_copying_the_body<F>(spawnfn: F) where F: FnOnce(Box<Fn() + Send>) {
1107 let (tx, rx) = channel();
1109 let x: Box<_> = box 1;
1110 let x_in_parent = (&*x) as *const i32 as usize;
1112 spawnfn(Box::new(move|| {
1113 let x_in_child = (&*x) as *const i32 as usize;
1114 tx.send(x_in_child).unwrap();
1117 let x_in_child = rx.recv().unwrap();
1118 assert_eq!(x_in_parent, x_in_child);
1122 fn test_avoid_copying_the_body_spawn() {
1123 avoid_copying_the_body(|v| {
1124 thread::spawn(move || v());
1129 fn test_avoid_copying_the_body_thread_spawn() {
1130 avoid_copying_the_body(|f| {
1131 thread::spawn(move|| {
1138 fn test_avoid_copying_the_body_join() {
1139 avoid_copying_the_body(|f| {
1140 let _ = thread::spawn(move|| {
1147 fn test_child_doesnt_ref_parent() {
1148 // If the child refcounts the parent thread, this will stack overflow when
1149 // climbing the thread tree to dereference each ancestor. (See #1789)
1150 // (well, it would if the constant were 8000+ - I lowered it to be more
1151 // valgrind-friendly. try this at home, instead..!)
1152 const GENERATIONS: u32 = 16;
1153 fn child_no(x: u32) -> Box<Fn() + Send> {
1154 return Box::new(move|| {
1155 if x < GENERATIONS {
1156 thread::spawn(move|| child_no(x+1)());
1160 thread::spawn(|| child_no(0)());
1164 fn test_simple_newsched_spawn() {
1165 thread::spawn(move || {});
1169 fn test_try_panic_message_static_str() {
1170 match thread::spawn(move|| {
1171 panic!("static string");
1174 type T = &'static str;
1175 assert!(e.is::<T>());
1176 assert_eq!(*e.downcast::<T>().unwrap(), "static string");
1183 fn test_try_panic_message_owned_str() {
1184 match thread::spawn(move|| {
1185 panic!("owned string".to_string());
1189 assert!(e.is::<T>());
1190 assert_eq!(*e.downcast::<T>().unwrap(), "owned string".to_string());
1197 fn test_try_panic_message_any() {
1198 match thread::spawn(move|| {
1199 panic!(box 413u16 as Box<Any + Send>);
1202 type T = Box<Any + Send>;
1203 assert!(e.is::<T>());
1204 let any = e.downcast::<T>().unwrap();
1205 assert!(any.is::<u16>());
1206 assert_eq!(*any.downcast::<u16>().unwrap(), 413);
1213 fn test_try_panic_message_unit_struct() {
1216 match thread::spawn(move|| {
1219 Err(ref e) if e.is::<Juju>() => {}
1220 Err(_) | Ok(()) => panic!()
1225 fn test_park_timeout_unpark_before() {
1227 thread::current().unpark();
1228 thread::park_timeout(Duration::from_millis(u32::MAX as u64));
1233 fn test_park_timeout_unpark_not_called() {
1235 thread::park_timeout(Duration::from_millis(10));
1240 fn test_park_timeout_unpark_called_other_thread() {
1242 let th = thread::current();
1244 let _guard = thread::spawn(move || {
1245 super::sleep(Duration::from_millis(50));
1249 thread::park_timeout(Duration::from_millis(u32::MAX as u64));
1254 fn sleep_ms_smoke() {
1255 thread::sleep(Duration::from_millis(2));
1259 fn test_thread_id_equal() {
1260 assert!(thread::current().id() == thread::current().id());
1264 fn test_thread_id_not_equal() {
1265 let spawned_id = thread::spawn(|| thread::current().id()).join().unwrap();
1266 assert!(thread::current().id() != spawned_id);
1269 // NOTE: the corresponding test for stderr is in run-pass/thread-stderr, due
1270 // to the test harness apparently interfering with stderr configuration.